JP2008210889A - Bulk hetero-junction photoelectric converting element, photosensor array, and radiation image detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bulk hetero-junction photoelectric converting element for controlling deterioration of photoelectric conversion efficiency even when it is heated and also provide a photosensor array and a radiation image detector. <P>SOLUTION: The bulk hetero-junction photoelectric converting element 10 is provided with a bulk hetero layer formed by mixing a type P semiconductor material an a type N semiconductor material. In this bulk hetero-junction photoelectric converting element 10, a semiconductor material having a lower melting point of the type P semiconductor material and the type N semiconductor material is mixed in the amount more than that resulting in a mixing ratio giving the preset photoelectric conversion rate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bulk heterojunction photoelectric conversion element, an optical array sensor using the photoelectric conversion element, and a radiation image detector.

  Gretzel et al. Reported a dye-sensitized photoelectric conversion element (Gretzel cell) that has a performance close to that of an amorphous silicon photoelectric conversion element by forming a film of an organic dye having a photoelectric conversion function on a transparent electrode such as titanium oxide. (See Non-Patent Document 1). In recent years, a dye-sensitized photoelectric conversion element using a monomolecular film having fullerene has also been reported using a nanotechnology technique (see, for example, Patent Document 1 and Patent Document 2).

  Since these dye-sensitized photoelectric conversion elements are wet solar cells that are electrically connected to the counter electrode using a liquid redox electrolyte, the photoelectric conversion function is significantly reduced due to depletion of the electrolyte when used over a long period of time. There is concern that it will no longer function as a conversion element.

  In addition, as a photoelectric conversion element using an organic dye that does not use an electrolytic solution, a heterojunction type (laminated type) photoelectric conversion element in which an electron donor layer and an electron acceptor layer are sandwiched between a transparent electrode and a counter electrode, or A bulk heterojunction photoelectric conversion element in which a bulk hetero layer in which an electron donor and an electron acceptor are uniformly mixed is formed between a transparent electrode and a counter electrode has been proposed (see, for example, Patent Document 3). ).

  The operation principle of these photoelectric conversion elements will be described. First, holes and electrons are generated by the movement of electrons from the electron donor (or electron donor layer) to the electron acceptor (or electron acceptor layer) by photoexcitation. Then, due to the internal electric field, holes pass between the electron donors (or electron donor layer) and are carried to one electrode, and electrons pass between the electron acceptors (or electron acceptor layer) to the other electrode. Carried. As a result, a photocurrent is observed.

  In the heterojunction photoelectric conversion element, charge separation is performed only at the interface between the electron donor layer and the electron acceptor layer, so that the amount of generated charge is very small and the photoelectric conversion efficiency is low. On the other hand, in the bulk heterojunction photoelectric conversion element, since the electron acceptor and the electron donor are uniformly mixed, the interface is increased, thereby improving the light absorption rate. As a result, the photoelectric conversion efficiency is improved. It is expected to improve.

  An annealing process is known as means for improving the photoelectric conversion rate of such a bulk heterojunction photoelectric conversion element (see, for example, Non-Patent Document 2). The bulk hetero layer (film) of the photoelectric conversion element is crystallized from an amorphous state in each of one or both of an electron donor and an electron acceptor microscopically by annealing. This crystallization results in (1) an increase in mobility and (2) a percolation path, which is a direct charge transport path to the electrode in the bulk heterolayer, resulting in an improvement in carrier extraction efficiency. Two effects occur, and the photoelectric conversion efficiency is improved. The improvement in photoelectric conversion efficiency by this annealing treatment depends on the annealing temperature, and according to Non-Patent Document 2, an annealing temperature around 75 ° C. is optimal for obtaining the highest photoelectric conversion efficiency. When heat treatment is performed at a temperature equal to or higher than the optimum annealing temperature, the crystallinity deteriorates and the light absorptance deteriorates. As a result, the photoelectric conversion efficiency deteriorates.

  In addition, in order to use such a bulk heterojunction photoelectric conversion element as a device, there is a manufacturing process involving a heat treatment such as a protective film forming process as a post process. The protective film needs various functions such as a damage preventing function for preventing mechanical damage and a function of preventing intrusion of deteriorated substances for preventing invasion of water, oxygen and the like which deteriorate the performance of the organic semiconductor. In order to form a protective film having these functions, the bulk heterojunction photoelectric conversion element is required to have heat resistance of 150 ° C. or higher, which is higher than the annealing temperature. The bulk heterojunction photoelectric conversion element can be applied to various devices. As an example, when considering application to a radiation image detector, a scintillator layer (film) that absorbs X-ray energy and emits fluorescence. ) Must be formed on the bulk heterojunction photoelectric conversion element. For this reason, the bulk heterojunction photoelectric conversion element is required to have heat resistance of 200 ° C. or higher, which is higher than the annealing temperature.

The crystallinity of the bulk hetero layer also depends on the mixing ratio of the electron donor and the electron acceptor, and there is an optimum mixing ratio that realizes the highest photoelectric conversion efficiency.
JP 2000-261016 A JP 2002-094146 A JP-T-2002-502129 Journal of the America Chemical Society 115 (1993) 6382 Franz Padinger, Advanced Functional Materials 13 (2003) 85-88

  The present invention has been made in view of the above circumstances, and its object is to provide a bulk heterojunction photoelectric conversion element that can further suppress deterioration in photoelectric conversion efficiency even when heated. is there. And it is providing the optical array sensor and radiographic image detector using this bulk heterojunction type photoelectric conversion element.

  As a result of various studies, the present inventor has found that the phenomenon of deterioration in photoelectric conversion efficiency when heated is caused by the following mechanism. That is, in a bulk hetero layer in which a P-type semiconductor material that functions relatively as an electron donor and an N-type semiconductor material that functions relatively as an electron acceptor are mixed at a predetermined mixing ratio, the predetermined mixing ratio The electron donor and the electron acceptor that were microscopically partially crystallized annealed at a temperature that gives the highest photoelectric conversion efficiency below were subjected to a heat treatment even higher than the temperature, Of the P-type semiconductor material and the N-type semiconductor material, the semiconductor material having a low melting point starts to melt, and as a result, it is rearranged and deviated from the optimum crystal state. That is, the crystallinity of the bulk hetero layer deteriorates and the photoelectric conversion efficiency deteriorates. Therefore, if the present inventor supplements a semiconductor material having a low melting point by the amount that crystallinity is lost by high-temperature heat treatment, even if the crystallinity of the bulk hetero layer is deteriorated by the high-temperature heat treatment, photoelectric conversion is performed. It came to the idea that degradation of efficiency is suppressed. Therefore, it has been found that the above object can be achieved by the present invention described below.

  That is, in one aspect of the present invention, in a bulk heterojunction photoelectric conversion element including a bulk hetero layer in which a P-type semiconductor material and an N-type semiconductor material are mixed, the P-type semiconductor material and the N-type semiconductor material The semiconductor material having a low melting point is richer than a mixing ratio that gives a preset photoelectric conversion rate. The semiconductor material having a low melting point is preferably a P-type semiconductor material.

  In the bulk heterojunction photoelectric conversion element having such a configuration, a semiconductor material having a low melting point out of a P-type semiconductor material and an N-type semiconductor material is richer than a mixture ratio that gives a preset photoelectric conversion rate. Since the semiconductor material with a low melting point is compensated by the amount of crystallinity collapsed by high-temperature heat treatment, even if the crystallinity of the bulk hetero layer is degraded by this high-temperature heat treatment, the deterioration of photoelectric conversion efficiency is suppressed. Is done.

  In particular, a semiconductor material having a melting point lower than the mixing ratio of the P-type semiconductor material and the N-type semiconductor material, which has the highest crystallinity, that is, the highest photoelectric conversion efficiency, is made rich. Even if the crystallinity of the bulk hetero layer is deteriorated, deterioration of the photoelectric conversion efficiency is suppressed, and high photoelectric conversion efficiency is realized. Then, considering the heat history such as the maximum temperature and the heating time in the manufacturing process, the semiconductor material having a low melting point is appropriately made rich by the amount of crystallinity collapsed by the heat treatment in this manufacturing process. Even if the crystallinity of the bulk hetero layer is deteriorated by a simple heat treatment, the deterioration of the photoelectric conversion efficiency is appropriately suppressed, and the substantially highest photoelectric conversion efficiency is realized.

  In these bulk heterojunction photoelectric conversion elements, the P-type semiconductor material is poly-3-hexylthiophene or poly-3-octylthiophene.

  According to this configuration, since the P-type semiconductor material is poly-3-hexylthiophene or poly-3-octylthiophene, high photoelectric conversion efficiency can be obtained.

  In the above bulk heterojunction photoelectric conversion element, the N-type semiconductor material is a fullerene derivative.

  According to this configuration, since the N-type semiconductor material is a fullerene derivative, high photoelectric conversion efficiency can be obtained. Here, fullerene derivatives are PCBM, PCBNB, PCBIB, C70-based PCBM (for example, URL; http://www.f-carbon.com/product_spectra.html#01 (February 23, 2007) Day search, Internet), G. Yu et al, Science, 1995, 270, 1789, L Zheng et al, J. Phys. Chem. B 2004, 108, 11921-6).

  Furthermore, in the above-described bulk heterojunction photoelectric conversion element, the P-type semiconductor material is poly-3-hexylthiophene, the N-type semiconductor material is a fullerene derivative, and the P-type semiconductor material is enriched. The amount is 15% or less by weight.

  According to this configuration, when the P-type semiconductor material is poly-3-hexylthiophene and the N-type semiconductor material is a fullerene derivative, the amount by which the P-type semiconductor material is enriched is 15% or less by weight. Thus, since the semiconductor material having a low melting point is optimally supplemented, the deterioration of the photoelectric conversion efficiency is most suppressed.

  In the bulk heterojunction photoelectric conversion element described above, the P-type semiconductor material is poly-3-octylthiophene, the N-type semiconductor material is a fullerene derivative, and the P-type semiconductor material is enriched. The amount is 20% or less by weight.

  According to this configuration, when the P-type semiconductor material is poly-3-octylthiophene and the N-type semiconductor material is a fullerene derivative, the amount of the P-type semiconductor material to be enriched is 20% by weight. By making the following, since the semiconductor material having a low melting point is optimally supplemented, the deterioration of the photoelectric conversion efficiency is most suppressed.

  In the above-described bulk heterojunction photoelectric conversion element, the bulk hetero layer is annealed.

  According to this configuration, since the bulk hetero film is annealed, the photoelectric conversion rate is improved. And even if the temperature of annealing treatment is comparatively high, since the semiconductor material with low melting | fusing point is rich, deterioration of photoelectric conversion efficiency is suppressed more.

  Furthermore, in the above bulk heterojunction photoelectric conversion element, the annealing temperature is approximately the melting point of a semiconductor material having a low melting point.

  According to this configuration, since the annealing temperature is substantially the melting point of the semiconductor material having a low melting point, the amount of crystallinity collapse due to the annealing treatment is effectively compensated, so that the deterioration in photoelectric conversion efficiency is effective. To be suppressed.

  An optical sensor array according to another embodiment of the present invention is characterized in that the bulk heterojunction photoelectric conversion elements described above are arranged in an array.

  According to this structure, even when heated in the manufacturing process, an optical sensor array that can further suppress deterioration in photoelectric conversion efficiency is provided.

  In another aspect of the present invention, a first layer that emits light according to the intensity of incident radiation, a second layer that converts light energy output from the first layer into electrical energy, and the first layer And a third layer for outputting a signal based on the accumulated electric energy obtained in the two layers and the third layer for outputting a signal based on the accumulated electric energy. It has a bulk hetero layer of a terror junction type photoelectric conversion element.

  According to this configuration, a radiation image detector that can further suppress deterioration in photoelectric conversion efficiency even when heated in the manufacturing process is provided.

  In the bulk heterojunction photoelectric conversion element according to the present invention, deterioration in photoelectric conversion efficiency is further suppressed even when heated. And according to this invention, the optical array sensor and radiographic image detector using this bulk heterojunction type photoelectric conversion element are provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.
(First embodiment)
FIG. 1 is a cross-sectional view illustrating an example of a bulk heterojunction photoelectric conversion element according to the first embodiment. In FIG. 1, a bulk heterojunction photoelectric conversion element 10 is formed by sequentially laminating a transparent electrode 12, a bulk hetero layer photoelectric conversion portion 14, and a counter electrode 13 on one surface of a substrate 11.

  The substrate 11 is a member that holds the transparent electrode 12, the photoelectric conversion unit 14, and the counter electrode 13 that are sequentially stacked. In the present embodiment, since light that is photoelectrically converted enters from the substrate 11 side, the substrate 11 can transmit the light that is photoelectrically converted, that is, with respect to the wavelength of the light to be photoelectrically converted. It is a transparent member. As the substrate 11, for example, a glass substrate or a resin substrate is used. The substrate 11 is not essential. For example, the bulk heterojunction photoelectric conversion element 10 may be configured by forming the transparent electrode 12 and the counter electrode 13 on both surfaces of the photoelectric conversion unit 14.

The transparent electrode 12 is an electrode that can transmit light that is photoelectrically converted in the photoelectric conversion unit 14, and is preferably an electrode that transmits light of 300 to 800 nm. As a material, for example, a transparent conductive metal oxide such as indium tin oxide (ITO), SnO ₂ , or ZnO, a metal thin film such as gold, silver, or platinum, or a conductive polymer can be used.

  The counter electrode 13 can be made of metal (for example, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon, or the material of the transparent electrode 12, but is not limited thereto.

  In the bulk heterojunction photoelectric conversion element 10 shown in FIG. 1, the photoelectric conversion unit 14 is sandwiched between the transparent electrode 12 and the counter electrode 13, but the pair of comb-like electrodes are arranged on one side of the photoelectric conversion unit 14. The bulk heterojunction photoelectric conversion element 10 may be configured by adopting an electrode configuration.

  The photoelectric conversion unit 14 is a layer that converts light energy into electric energy, and includes a bulk hetero layer in which a P-type semiconductor material and an N-type semiconductor material are uniformly mixed. The P-type semiconductor material functions relatively as an electron donor (donor), and the N-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons as in the case of an electrode, but donates or accepts electrons by a photoreaction.

  As the P-type semiconductor material, in order to realize relatively high photoelectric conversion efficiency, for example, poly-3-hexylthiophene (hereinafter abbreviated as “P3HT”) and poly-3-octylthiophene (hereinafter, “P3OT”). Is abbreviated as ")". As the N-type semiconductor material, for example, a fullerene derivative such as PCBIB (Phenyl C61-butylic acid i-butyl ester) is used in order to realize relatively high photoelectric conversion efficiency.

  Examples of a method for forming a bulk hetero layer in which an electron acceptor and an electron donor are mixed include a vapor deposition method and a coating method (including a casting method and a spin coating method). Among these, a coating method is particularly preferable.

  Then, the bulk hetero layer of the photoelectric conversion unit 14 is annealed at a predetermined temperature during the manufacturing process so as to improve the photoelectric conversion rate, and is partially crystallized microscopically.

  In FIG. 1, light incident from the transparent electrode 12 through the substrate 11 is absorbed by the electron acceptor or electron donor in the bulk hetero layer of the photoelectric conversion unit 14, and electrons move from the electron donor to the electron acceptor. A hole-electron pair (charge separation state) is formed. The generated electric charge is caused by an internal electric field, for example, when the work functions of the transparent electrode 12 and the counter electrode 13 are different, the electrons pass between the electron acceptors due to the potential difference between the transparent electrode 12 and the counter electrode 13, and the holes are , Passed between the electron donors and carried to different electrodes, and photocurrent is detected. For example, when the work function of the transparent electrode 12 is larger than the work function of the counter electrode 13, electrons are transported to the transparent electrode 12 and holes are transported to the counter electrode 13. If the magnitude of the work function is reversed, electrons and holes are transported in the opposite direction. In addition, by applying a potential between the transparent electrode 12 and the counter electrode 13, the transport direction of electrons and holes can be controlled.

  Here, it should be noted that in the bulk hetero layer of the photoelectric conversion unit 14, a semiconductor material having a low melting point out of the P-type semiconductor material and the N-type semiconductor material has a preset mixing ratio that gives a predetermined photoelectric conversion rate. Be rich.

  Since the semiconductor material having a low melting point is richer than a preset mixing ratio that gives a predetermined photoelectric conversion rate, a semiconductor having a low melting point is subjected to heat treatment such as annealing at a temperature higher than the melting point. Even if the material is melted, it is rich, so that the crystallinity sufficient to give a predetermined photoelectric conversion efficiency set in advance is maintained, and deterioration of the photoelectric conversion efficiency can be suppressed.

  In order to produce such a bulk hetero layer of the photoelectric conversion unit 14, elements A and B are produced using the mixing ratio of the P-type semiconductor material and the N-type semiconductor material and the annealing temperature as parameters. In order to evaluate the rate, crystallinity that can serve as an index was evaluated by an X-ray diffractometer (XRD).

(Example 1)
In the device A, P3HT was used as a P-type semiconductor material, and PCBIB, which is one of fullerene derivatives, was used as an N-type semiconductor material. P3HT has a melting point of about 208 ° C. and PCBIB has a melting point of about 280 ° C. Therefore, the semiconductor material having a low melting point is P3HT, which is a P-type semiconductor material.

  First, Merck P3HT was dissolved in chlorobenzene solvent at an addition amount of 3% by weight, and ultrasonically stirred for 5 minutes, and Frontier Carbon's PCBIB was dissolved in chlorobenzene solvent at an addition amount of 3% by weight. The ultrasonically stirred solution was mixed for 5 minutes at each mixing ratio. Each mixing ratio is P3HT: PCIBB = 0.2: 1, 0.4: 1, 0.6: 1, 0.8: 1, 1: 1, 1: 0.8, 1: 0.6, 1 : 0.4, 1: 0.2. The mixing ratio of P3HT is approximately 16.7%, approximately 28.6%, 37.5%, approximately 44.4%, 50%, approximately 55.6%, 62.5%, approximately 71.4% by weight. %, About 83.3%. Next, this mixed solution was ultrasonically stirred for 5 minutes, and the resulting mixed solution was spin-coded on the cleaned glass substrate. And this glass substrate was heated at each temperature in the oven of atmospheric pressure and nitrogen atmosphere, and the annealing process was carried out, and the element A was produced. Each temperature of annealing treatment is 25 degreeC, 50 degreeC, 100 degreeC, 150 degreeC, 200 degreeC, 250 degreeC. The thickness of the mixed liquid layer (bulk hetero layer) after the annealing treatment was about 100 nm.

  FIG. 2 is a graph showing the relationship between the mixing ratio of P3HT and crystallinity in the element A. The horizontal axis of FIG. 2 shows the mixing ratio of P3HT expressed in%, and the vertical axis of the X-ray diffraction apparatus in the case of the best crystallinity (when the mixing ratio of P3HT is about 44.4%). The crystallinity normalized by the output value is shown. ◆ and ■ show measured values, ◆ shows the case of annealing at 100 ° C., and ■ shows the case of annealing at 200 ° C.

  FIG. 3 is a diagram showing the relationship between the annealing temperature and crystallinity in the element A. The horizontal axis in FIG. 3 indicates the annealing temperature expressed in ° C., and the vertical axis is normalized by the output value of the X-ray diffractometer when the crystallinity is the best (when the annealing temperature is 100 ° C.). The crystallinity exhibited. ◆ and ■ show measured values, ◆ shows the case of P3HT: PCIBB = 0.8: 1, and ■ shows the case of P3HT: PCIBB = 1: 0.8.

  As can be seen from FIG. 2, when the annealing temperature is 100 ° C. at which neither the P-type nor the N-type semiconductor material is melted, the mixing ratio of P3HT is about 16.7 (= (0.2 / (0. 2 + 1)) × 100)% to about 44.4 (= (0.8 / (0.8 + 1)) × 100)%, the crystallinity is improved, and the mixing ratio of P3HT is about 44.4%. The crystallinity deteriorates as it increases to about 83.3 (= (1 / (1 + 0.2)) × 100)%. On the other hand, when the annealing temperature is 200 ° C., the crystallinity increases as the mixing ratio of P3HT increases from about 16.7% to about 55.6 (= (1 / (1 + 0.8)) × 100)%. The crystallinity deteriorates as the mixing ratio of P3HT increases from about 55.6% to about 83.3%.

  Therefore, when the annealing temperature increases from 100 ° C. to 200 ° C., the mixing ratio with the best crystallinity shifts from P3HT: PCIBB = 0.8: 1 to P3HT: PCIBIB = 1: 0.8. That is, the mixing ratio of P3HT is increased from 44.4% to 55.6% by weight. The amount that enriches P3HT in this case is about 55.56-about 44.44 = about 11.1% by weight.

  Then, when the relationship between the annealing temperature and crystallinity in the case of the mixing ratio P3HT: PCIBIB = 0.8: 1 and the mixing ratio P3HT: PCIBIB = 1: 0.8 is examined, the result of FIG. 3 is obtained. It was. That is, as can be seen from FIG. 3, in the case of the mixing ratio P3HT: PCIBIB = 0.8: 1 with the best crystallinity, the crystallinity is improved as the annealing temperature increases from 25 ° C. to 100 ° C. As the annealing temperature increases from 100 ° C. to 250 ° C., the crystallinity deteriorates. Crystallinity is best when the annealing temperature is 100 ° C. On the other hand, in the case of the mixing ratio P3HT: PCIBB = 1: 0.8 in which the relatively low melting point P3HT is rich, the crystallinity is improved as the annealing temperature is increased from 25 ° C. to 100 ° C., Even when the annealing temperature is increased from 100 ° C. to 200 ° C., the crystallinity is hardly changed (degradation of crystallinity is suppressed), and as the annealing temperature is increased from 200 ° C. to 250 ° C., the crystallinity is improved. to degrade. When the annealing temperature is in the range of 100 ° C. to 200 ° C., deterioration of crystallinity is suppressed and good crystallinity is substantially maintained.

  Therefore, when P3HT having a melting point lower than the mixing ratio P3HT: PCIBB = 0.8: 1 having the best crystallinity is made rich, the deterioration of crystallinity is suppressed and the crystallinity is improved. Since the crystallinity and the photoelectric conversion rate are correlated with each other, when P3HT having a melting point lower than the mixing ratio P3HT: PCIBB = 0.8: 1 having the highest photoelectric conversion efficiency is made rich, a decrease in the photoelectric conversion rate is suppressed. . In particular, when the mixing ratio P3HT: PCIBB = 0.8: 1, relatively good crystallinity is substantially maintained over a temperature range of 100 ° C. to 200 ° C., and high photoelectric conversion efficiency is substantially maintained. .

  As can be seen from FIGS. 2 and 3, from the viewpoint of suppressing the deterioration of crystallinity, that is, optimally suppressing the decrease in photoelectric conversion efficiency, the P-type semiconductor material is P3HT and the N-type semiconductor material is the fullerene group. In the bulk hetero layer which is a living organism, the amount of enrichment of P3HT is preferably 15% or less by weight, and particularly the amount of enrichment of P3HT is preferably about 11.1% by weight.

(Example 2)
For element B, P3OT was used as the P-type semiconductor material, and PCBIB was used as the N-type semiconductor material. The melting point of P3OT is about 165 ° C. Therefore, the semiconductor material having a low melting point is P3OT which is a P-type semiconductor material.

  First, P3OT manufactured by ADS is dissolved in a chlorobenzene solvent at an addition amount of 2% by weight, and an ultrasonically stirred solution for 5 minutes and PCBIB manufactured by Frontier Carbon Co. are dissolved in a chlorobenzene solvent at an addition amount of 2% by weight. The ultrasonically stirred solution was mixed for 5 minutes at each mixing ratio. Each mixing ratio is P3OT: PCIBB = 0.2: 1, 0.4: 1, 0.6: 1, 0.8: 1, 1: 1, 1: 0.8, 1: 0.6, 1 : 0.4, 1: 0.2. The mixing ratio of P3OT is about 16.7%, about 28.6%, 37.5%, about 44.4%, 50%, about 55.6%, 62.5%, about 71.4% by weight. %, About 83.3%. Next, this mixed solution was ultrasonically stirred for 5 minutes, and the resulting mixed solution was spin-coded on the cleaned glass substrate. And this glass substrate was heated at each temperature in the oven of atmospheric pressure and nitrogen atmosphere, and the annealing process was carried out, and the element B was produced. Each temperature of annealing treatment is 25 degreeC, 50 degreeC, 100 degreeC, 150 degreeC, and 200 degreeC. The thickness of the mixed liquid layer (bulk hetero layer) after the annealing treatment was about 55 nm.

  FIG. 4 is a diagram showing the relationship between the mixing ratio of P3OT and the crystallinity in the element B. The horizontal axis of FIG. 4 shows the mixing ratio of P3OT expressed in units of%, and the vertical axis of the X-ray diffraction apparatus in the case of the best crystallinity (when the mixing ratio of P3OT is about 55.6%). The crystallinity normalized by the output value is shown. ◆ and ■ show measured values, ◆ shows the case of annealing at 150 ° C., and ■ shows the case of annealing at 200 ° C.

  FIG. 5 is a diagram showing the relationship between the annealing temperature and crystallinity in the element B. In FIG. The horizontal axis in FIG. 5 indicates the annealing temperature expressed in ° C., and the vertical axis is normalized by the output value of the X-ray diffractometer when the crystallinity is the best (when the annealing temperature is 150 ° C.). The crystallinity exhibited. ◆ and ■ show measured values, ◆ shows the case of P3OT: PCBIB = 1: 0.8, and ■ shows the case of P3OT: PCBIB = 1: 0.4.

  As can be seen from FIG. 4, when the annealing temperature is 150 ° C., the crystallinity is improved as the mixing ratio of P3OT is increased from about 16.7% to about 55.6%, and the mixing ratio of P3OT is about Crystallinity deteriorates as it increases from 55.6% to about 83.3%. On the other hand, when the annealing temperature is 200 ° C., the crystallinity increases as the mixing ratio of P3OT increases from about 16.7% to about 71.4 (= (1 / (1 + 0.4)) × 100)%. The crystallinity deteriorates as the mixing ratio of P3OT increases from about 71.4% to about 83.3%.

  Therefore, when the annealing temperature increases from 150 ° C. to 200 ° C., the mixing ratio with the best crystallinity shifts from P3OT: PCBIB = 1: 0.8 to P3OT: PCBIB = 1: 0.4. That is, the mixing ratio of P3OT is increased from about 55.6% to about 71.4% by weight. In this case, the amount that makes P3OT rich is about 71.43 to about 55.56 = about 15.9% by weight.

  When the relationship between the annealing temperature and crystallinity in the case of the mixing ratio P3OT: PCIBIB = 1: 0.8 and the mixing ratio P3OT: PCIBIB = 1: 0.4 is examined, the result of FIG. 5 is obtained. It was. That is, as can be seen from FIG. 5, in the case of the mixing ratio P3OT: PCBIB = 1: 0.8 having the best crystallinity, the crystallinity is improved as the annealing temperature increases from 25 ° C. to 150 ° C. As the annealing temperature rises from 150 ° C. to 200 ° C., the crystallinity rapidly deteriorates. Crystallinity is best when the annealing temperature is 150 ° C. On the other hand, in the case of P3OT: PCIBIB = 1: 0.4 in which P3OT having a relatively low melting point is enriched, the crystallinity is improved and the annealing treatment is performed as the annealing temperature increases from 25 ° C. to 150 ° C. Even when the temperature rises from 150 ° C. to 200 ° C., the deterioration of crystallinity is moderate. When the annealing temperature is in the range of 150 ° C. to 200 ° C., deterioration of crystallinity is suppressed, and good crystallinity is substantially maintained.

  Therefore, when P3OT having a melting point lower than the mixing ratio P3OT: PCBIB = 1: 0.8 having the best crystallinity is made rich, crystallinity deterioration is suppressed and crystallinity is improved. That is, when P3OT having a melting point lower than the mixing ratio P3OT: PCBIB = 1: 0.8 having the highest photoelectric conversion efficiency is made rich, a decrease in photoelectric conversion rate is suppressed. In particular, when the mixing ratio P3OT: PCIBB = 1: 0.4, relatively good crystallinity is substantially maintained over a temperature range of 150 ° C. to 200 ° C., and high photoelectric conversion efficiency is substantially maintained. .

  As can be seen from FIGS. 4 and 5, from the viewpoint of suppressing the deterioration of crystallinity, that is, suppressing the decrease in photoelectric conversion efficiency, the P-type semiconductor material is P3OT, and the N-type semiconductor material is a fullerene derivative. In a certain bulk hetero layer, the amount of P3OT enriched is preferably 20% or less by weight, and in particular, the amount of P3OT enriched is preferably about 15.9% by weight.

  As described above, among the P-type semiconductor material and the N-type semiconductor material in the bulk hetero layer, a semiconductor material having a low melting point is made richer than a mixture ratio that gives a preset photoelectric conversion rate, so that high-temperature heat treatment is performed. Since the semiconductor material having a low melting point is compensated for by the collapse of the crystallinity, even if the crystallinity of the bulk hetero layer is deteriorated by this high-temperature heat treatment, the deterioration of the photoelectric conversion efficiency can be suppressed.

  In particular, a semiconductor material having a melting point lower than the mixing ratio of the P-type semiconductor material and the N-type semiconductor material, which has the highest crystallinity, that is, the highest photoelectric conversion efficiency, is made rich. Even if the crystallinity of the bulk hetero layer deteriorates, the deterioration of the photoelectric conversion efficiency is suppressed, and a high photoelectric conversion efficiency can be realized. Then, considering the heat history such as the maximum temperature and the heating time in the manufacturing process, the semiconductor material having a low melting point is appropriately made rich by the amount of crystallinity collapsed by the heat treatment in this manufacturing process. Even if the crystallinity of the bulk hetero layer deteriorates due to a simple heat treatment, the deterioration of the photoelectric conversion efficiency is appropriately suppressed, and the substantially highest photoelectric conversion efficiency can be realized.

  And since the temperature at which heat treatment is performed is substantially the same as that of a semiconductor material having a low melting point, the amount of loss of crystallinity caused by heat treatment is effectively compensated, so that deterioration in photoelectric conversion efficiency can be effectively suppressed. It becomes.

  Returning to FIG. 1, the photoelectric conversion unit 14 may be configured as a single layer in which the electron acceptor and the electron donor are uniformly mixed. However, the mixing ratio of the electron acceptor and the electron donor is set to be different. You may comprise by the changed multiple layer.

  In a photoelectric conversion element in which a layer in which an electron donor and an electron acceptor are mixed is formed between the electrodes, when the electron acceptor and the electron donor are mixed uniformly, the electrons and holes generated after charge separation are charged. Recombination is likely to occur during transportation, and this can be a factor that lowers the photoelectric conversion efficiency. Therefore, the photoelectric conversion unit 14 includes a plurality of layers in which an electron acceptor and an electron donor are mixed, and causes a decrease in device performance by changing the mixing ratio of the electron acceptor and the electron donor in each layer. It is possible to solve the problem of charge generation amount and the problem of charge transport after charge separation. For example, a layer with a high mixing ratio of the electron acceptor is arranged on the electrode side for collecting electrons, and a layer with a high mixing ratio of the electron donor is arranged on the electrode side for collecting holes, The recombination probability during charge transport can be lowered while keeping the generated charge amount large.

  Further, the above-described bulk heterojunction photoelectric conversion element 10 includes the transparent electrode 12, the photoelectric conversion portion 14 of the bulk hetero layer, and the counter electrode 13 that are sequentially stacked on the substrate 11, but is not limited thereto. For example, the bulk heterojunction photoelectric conversion element 10 may be configured by including another layer such as an insulating layer or an undercoat layer between the transparent electrode 12 or the counter electrode 13 and the photoelectric conversion unit 14.

(Second Embodiment)
Next, an embodiment of an optical sensor array to which the bulk heterojunction photoelectric conversion element 10 described above is applied will be described in detail.

  FIG. 6 is a diagram showing the configuration of the photosensor array in the second embodiment. 6A is a top view, and FIG. 6B is a cross-sectional view taken along the line A-A ′ of FIG.

  In FIG. 12, an optical sensor array 20 is paired with a transparent electrode 22 as a lower electrode, a photoelectric conversion unit 24 for converting light energy into electric energy, and a transparent electrode 22 on a substrate 21 as a holding member. The counter electrode 23 is sequentially laminated. The photoelectric conversion unit 24 includes two layers, a photoelectric conversion layer 24b having a bulk hetero layer in which a P-type semiconductor material and an N-type semiconductor material are uniformly mixed, and a buffer layer 24a. In the example shown in FIG. 6, six bulk heterojunction photoelectric conversion elements are formed.

  The substrate 21, the transparent electrode 22, the photoelectric conversion layer 24b, and the counter electrode 23 have the same configuration and role as the transparent electrode 12, the photoelectric conversion unit 14, and the counter electrode 13 in the bulk heterojunction photoelectric conversion element 10 described above. is there.

  For example, glass is used for the substrate 21, ITO is used for the transparent electrode 22, and aluminum is used for the counter electrode 23, for example. For example, P3HT is used as the P-type semiconductor material of the photoelectric conversion layer 24b, and PCB ([6,6] -phenyl C61-butyl acid acid methyl), which is one of fullerene derivatives, is used as the N-type semiconductor material. ester) is used. The buffer layer 24a is made of PEDOT (poly-3,4-ethylenedioxythiophene) -PSS (polystyrene sulfonic acid) conductive polymer (trade name BaytronP, manufactured by Stark Vitec). Such an optical sensor array 20 was manufactured as follows.

  An ITO film was formed on the glass substrate by sputtering and processed into a predetermined pattern shape by photolithography. The thickness of the glass substrate was 0.7 mm, the thickness of the ITO film was 200 nm, and the measurement area (light receiving area) of the ITO film after photolithography was 5 mm × 5 mm. Next, a PEDOT-PSS film was formed on the glass substrate 21 by spin coating (conditions: rotational speed = 1000 rpm, filter diameter = 1.2 μm). Thereafter, the substrate was heated in an oven at 100 ° C. for 30 minutes and dried. The thickness of the PEDOT-PSS film after drying was 90 nm.

  Next, a P3HT + PCBM mixed film was formed on the PEDOT-PSS film by a spin coating method (conditions: rotational speed = 1500 rpm, filter diameter = 0.8 μm). In this spin coating, P3HT was dissolved in a chloroform solvent (addition amount 1% by weight) with ultrasonic stirring (5 minutes), and PCBM was dissolved in a chloroform solvent (addition amount 1% by weight) with ultrasonic stirring (5%). The mixture was mixed at a mixing ratio P3HT: PCBM = 1.0: 1.0 (optimal conditions were 0.6: 1.0 at 75 ° C.) (weight ratio). A mixture obtained by ultrasonic stirring (5 minutes) was used. After the formation of the P3HT + PCBM mixed film, annealing was performed by heating in an oven at 100 ° C. for 30 minutes in a nitrogen gas atmosphere. The thickness of the P3HT + PCBM mixed film after the annealing treatment was 70 nm.

  Thereafter, using a metal mask having a predetermined pattern opening, an aluminum layer as an upper electrode was formed on the P3HT + PCBM mixed film by a vapor deposition method (thickness = 10 nm). Thereafter, 1 μm of PVA (polyvinyl alcohol) was formed by spin coating and baked at 150 ° C. to prepare a passivation layer (not shown). The optical sensor array 20 was produced as described above.

In the optical sensor array 20 in the present embodiment, the semiconductor material having a low melting point out of the P-type semiconductor material and the N-type semiconductor material in the bulk hetero layer is richer than the mixing ratio that gives a preset photoelectric conversion rate. Since the semiconductor material having a low melting point is supplemented by the amount that the crystallinity is destroyed by the annealing treatment, even if the crystallinity of the bulk hetero layer is deteriorated by this annealing treatment, the deterioration of the photoelectric conversion efficiency is suppressed.
(Third embodiment)
Next, an embodiment of a system using a radiation image detector to which the bulk heterojunction photoelectric conversion element 10 and the optical sensor array described above are applied will be described in detail.

  FIG. 7 is a block diagram showing an image detection system using the radiation image detector in the third embodiment. The image detection system S includes a radiation image detector 3, a radiation generator 4, a processing control unit 5, and a network device unit 6.

  The processing control unit 5 includes, for example, a computer such as a personal computer, and includes an image processing unit 51, an image display unit 52, an information input unit 53, an image output unit 54, an image storage unit 55, and computer-aided image automatic processing. And a diagnosis unit (CAD) 56. The network device unit 6 includes a network 60 with a CT (computerized tomography) 61, an MRI (magnetic resonance imaging) 62, an X-ray imaging device 63 such as a CR (computed radiography) or an FPD (Flat Panel Detector), an external image storage device 64, and the like. An external image display device 65 is connected.

  In FIG. 7, the radiation emitted from the radiation generator 4 that generates and emits radiation is irradiated to the radiation image detector 3 through a subject (for example, a patient in a medical facility) H. The radiation image detector 3 generates an image signal DFE based on the intensity of the irradiated radiation. The generated image signal DFE is read by the image processing unit 51 connected to the radiation image detector 3. Alternatively, the image signal DFE is accumulated in a portable recording medium such as a semiconductor memory card attached to the radiation image detector 3, and then the recording medium is removed from the radiation image detector 3 and is sent to the image processing unit 51. By being mounted, the image processing unit 51 is supplied.

  In the image processing unit 51, image processing such as shading correction, gain correction, gradation correction, edge enhancement processing, frequency processing, dynamic range compression processing, and the like is performed on the image signal DFE generated by the radiation image detector 3. The Thereby, an image signal suitable for diagnosis or the like is output. Further, an image display unit 52 is connected to the image processing unit 51, and an image generated based on the image signal after image processing output from the image processing unit 51 is displayed on the image display unit 52. The

  In addition, the image processing unit 51 can perform enlargement and reduction of the image, and also performs compression and expansion processing of the image signal in order to facilitate storage and transfer of the image signal. For this reason, it is possible to easily confirm the imaging region by enlarging / reducing the image displayed on the image display unit 52. In addition, the image processing unit 51 automatically designates the displayed image and the area of the displayed image, and automatically performs appropriate image processing on the designated image and the designated area.

  For example, an operation input unit 53 having a keyboard, a mouse, a pointer, and the like is connected to the image processing unit 51. The user can input patient information or the like through the operation input unit 53 and add additional information to the image signal. The operation input unit 53 also gives instructions for specifying image processing, storing and reading image signals, and transmitting and receiving image signals via a network.

  The image output unit 54 records and outputs a radiation image on recording paper, film, or the like. For example, an imager may be used that exposes a silver salt photographic film based on an image signal and records and outputs a radiation image as a silver image by developing the exposed silver salt photographic film. Alternatively, the image output unit 54 is an ink jet printer that prints ink on recording paper or film by an ink jet method based on an image signal, and a thermal that transfers ink to the recording paper or film by melting or sublimating ink based on an image signal. A printer or an electrophotographic printer that forms an image on recording paper by scanning the photosensitive member with laser light based on an image signal, transferring the toner adhering to the photosensitive member to paper, and fixing it with heat and pressure It may be.

  The image storage unit 55 is composed of an information recording medium having a relatively large storage capacity such as a hard disk or a DVD-R (Digital Versatile Disc Recordable), for example, so that an image signal of a radiographic image can be read as needed. It is something to save.

  The CAD 56 provides information useful for diagnosis to a doctor so that the diagnosis is supported so that there is no oversight of the lesion, and the computerized image processing and computer analysis of the captured radiographic image is performed to obtain information useful for the diagnosis. Append to signal.

  The image processing unit 51 can send the radiographic image signal not only to the image output unit 54, the image storage unit 55, and the CAD 56 described above, but also to the network device unit 6. That is, an image signal of a radiographic image can be sent to other departments in a hospital facility or a remote place via a network 60 such as a so-called LAN, the Internet, and a PACS (medical image network).

  Further, the image processing unit 51 also receives an image signal obtained from the CT 61 or MRI 62 or an image signal obtained from the X-ray imaging apparatus 63 such as CR or FPD, and other inspection information via this network. In order to compare with the radiographic image obtained by the radiographic image detector 3, the image signal or examination information sent via the network 60 is displayed on the image display unit 52 or output from the image output unit 54. You can also. Furthermore, the image processing unit 51 can store the transmitted image signal, inspection information, and the like in the image storage unit 55. In addition, the image processing unit 51 stores the image signal of the radiographic image obtained by the radiographic image detector 20 in the external image storage device 64, or displays the radiographic image detector 3 on the screen of the external image display device 65. The obtained radiation image can also be displayed.

  FIG. 8 is a partially broken perspective view showing an example of the structure of the radiation image detector in the third embodiment. The radiation image detector 3 includes an imaging panel 31, a scanning drive circuit 32, a signal selection circuit 33, a control circuit 34, a memory unit 35, an operation unit 36, a display unit 37, a power supply unit 38, and a connector. 39 and a housing 300.

  The imaging panel 31 generates accumulated electrical energy according to the intensity of irradiated radiation, and includes a surface on which many of the photoelectric conversion elements described above are arranged in an array (two-dimensional matrix). The imaging panel 31 is also an embodiment of an optical sensor array. The electrical energy generated by the imaging panel 31 is read by the scanning drive circuit 32 and output as an image signal by the signal selection circuit 33. The output image signal is stored in a memory unit 35 including a rewritable read-only memory (for example, a flash memory). The operation of the radiation image detector 3 is controlled by the control circuit 34, and the operation is switched by the operation unit 36.

  The display unit 37 is used to display that image preparation has been completed and that a predetermined amount of image signal has been written in the memory unit 35. The power supply unit 38 supplies power required to drive the imaging panel 31 and obtain an image signal. The connector 39 is for performing communication between the radiation image detector 3 and the image processing unit 51. The inside of the housing 300, the scanning drive circuit 32, the signal selection circuit 33, the control circuit 34, the memory unit 39, and the like are covered with a radiation shielding member (not shown). The radiation shielding member prevents radiation scattering inside the housing 300 and irradiation of radiation to each circuit.

  The housing 300 is for housing the above-described components. The housing 300 is preferably made of a material that can withstand external impact and is as light as possible, such as aluminum or an alloy thereof. The radiation incident surface side of the housing 300 is configured using a non-metal that easily transmits radiation, such as carbon fiber. Further, on the back side opposite to the radiation incident surface, it is generated for the purpose of preventing the radiation from passing through the radiation image detector 3 or by the material constituting the radiation image detector 3 absorbing the radiation. For the purpose of preventing the influence from secondary radiation, it is preferable to use a material that effectively absorbs radiation, such as a lead plate.

  FIG. 9 is a circuit diagram illustrating a circuit configuration of the imaging panel according to the third embodiment. The imaging panel 31 has a two-dimensional arrangement of collecting electrodes 310 for reading out electrical energy stored in accordance with the intensity of irradiated radiation. The collecting electrode 310 is used as one electrode of the capacitor 311, and electric energy is stored in the capacitor 311. Here, one collecting electrode 310 corresponds to one pixel of the radiation image.

  Here, in this specification, when referring generically, it shows with the reference symbol which abbreviate | omitted the suffix, and when referring to an individual structure, it shows with the reference symbol which attached the suffix.

  Between the pixels, the scanning lines 313-1 to 313-m and the signal lines 314-1 to 314-n are disposed so as to be orthogonal, for example. In the example shown in FIG. 9, three scanning lines 313-1 to 333-3 and three signal lines 314-1 to 314-3 are illustrated. The capacitor 311-(1, 1) is connected to a transistor 312-(1, 1) made of a silicon laminated structure or an organic semiconductor. The transistor 312- (1,1) is, for example, a field effect transistor, and the drain electrode or the source electrode is connected to the collection electrode 310- (1,1), and the gate electrode is connected to the scanning line 313-1. Connected. When the drain electrode is connected to the collecting electrode 310- (1,1), the source electrode is connected to the signal line 314-1, and when the source electrode is connected to the collecting electrode 310- (1,1) The drain electrode is connected to the signal line 314-1. Similarly, the scanning line 313 and the signal line 314 are connected to the collecting electrode 310, the capacitor 311 and the transistor 312 of other pixels. Reference numeral 316 represents a reset line.

FIG. 10 is a partial cross-sectional view (one pixel) of the imaging panel according to the third embodiment. A first layer 301 that emits light according to the intensity of incident radiation is provided on the radiation irradiation surface side of the imaging panel 31. Examples of radiation include X-rays. In this case, for example, the wavelength is about 0.1 nm (1 × 10 ⁻¹⁰ m), and X-rays that are electromagnetic waves that pass through a human body, a ship, an aircraft member, or the like are irradiated. This X-ray is output from the radiation generator 4, and the radiation generator 4 is generally a fixed anode or a rotary anode X-ray tube. In addition, the X-ray tube usually has an anode load voltage of 10 kV to 300 kV, and 20 kV to 150 kV when used for medical purposes.

  The first layer 301 is a scintillator having a phosphor as a main component, and emits fluorescence having a wavelength of 300 nm to 800 nm by incident radiation.

The phosphors used in the first layer 301 are tungstate phosphors such as CaWO ₄ , CaWO ₄ : Pb, MgWO, Y ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Tb, La ₂ O _2. S: Tb, (Y, Gd) ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Terbium-activated rare earth oxysulfide phosphors such as Tb, Tm, YPO ₄ : Tb, GdPO ₄ : Tb Terbium-activated rare earth phosphate phosphors such as LaPO ₄ : Tb, LaOBr: Tb, LaOBr: Tb, Tm, LaOCl: Tb, LaOCl: Tb, Tm, GdOBr: Tb, GdOBr: Tb, Tm, GdOCl: Tb, Terbium activated rare earth oxyhalide phosphors such as GdOCl: Tb, Tm, thulium activated rare earth oxyhalides such as LaOBr: Tm, LaOCl: Tm -Based phosphors, gadolinium-activated rare earth oxyhalide phosphors such as LaOBr: Gd, LuOCl: Gd, GdOBr: Ce, GdOCl: Ce, (Gd, Y) OBr: Ce, (Gd, Y) OCl: Ce, etc. Cerium-activated rare earth oxyhalide phosphors, BaSO ₄ : Pb, BaSO ₄ : Eu ²⁺ , (Ba, Sr) SO ₄ : Eu ^{2+ and} other barium sulfate phosphors, Ba ₃ (PO ₄ ) ₂ : Eu ²⁺ , (Ba ₂ PO ₄ ) ₂ : Eu ²⁺ , Sr ₃ (PO ₄ ) ₂ : Eu ²⁺ , (Sr ₂ PO ₄ ) ₂ : Eu ^2+, etc., a divalent europium activated alkaline earth metal phosphate phosphor, ^{BaFCl: Eu 2+, BaFBr: Eu} 2+, BaFCl: Eu 2+, Tb, BaFCl: Eu 2+, Tb, BaF 2 · BaCl 2 · K _{^{l: Eu 2+, (Ba,}} Mg) F 2 · BaCl 2 · KCl: 2 divalent europium activated alkaline earth metal fluoride halide phosphors ^{Eu 2+, CsI: Na, CsI} : Tl, NaI, KI: Iodide phosphors such as Tl, sulfide phosphors such as ZnS: Ag, (Zn, Cd) S: Ag, (Zn, Cd) S: Cu, (Zn, Cd) S: Cu, Ag, HfP ₂ O ₇ , HfP ₂ O ₇ : Cu, Hf ₂ (PO ₄ ) _4, etc., phosphoric hafnium-based phosphor, YTaO ₄ , YTaO ₄ : Tm, YTaO ₄ : Nb, (Y, Sr) TaO ₄ : Nb, LuTaO ₄ , LuTaO ₄ : Tm, LuTaO ₄ : Nb, (Lu, Sr) TaO ₄ : Nb, GdTaO ₄ : Tm, Mg ₄ Ta ₂ O ₉ : Nb, Gd ₂ O ₃ .Ta ₂ O ₅ .B ₂ O ₃ : Tb etc. Tantalum based phosphor, the ^{_{other, Gd 2 O 2 S: Eu}} 3+, (La, Gd, Lu) 2 Si 2 O 7: Eu, ZnSiO 4: Mn, Sr 2 P 2 O 7: the use of the Eu Can do.

In particular, cesium iodide (CsI: X, where X is an activator) and gadolinium oxysulfide (Gd ₂ O ₂ S: X, where X is an activator) are preferable because of their high X-ray absorption and luminous efficiency, and these are used. Thus, a high-quality image with low noise can be obtained.

  The scintillator preferably has a columnar crystal structure. In the columnar crystal, the light guide effect, that is, the effect of reducing the emission of light within the crystal from being emitted outside the side surface of the columnar crystal can be obtained. This is because increasing the body layer thickness increases X-ray absorption and improves graininess.

  The phosphor used in the present embodiment is not limited to these, and is a phosphor that outputs electromagnetic waves in a region where the light receiving element is sensitive, such as a visible, ultraviolet, or infrared region by irradiation of radiation. I need it. In addition, the diameter of the phosphor particles used in the present embodiment is preferably 7 μm or less, particularly 4 μm or less. This is because the smaller the diameter of the phosphor particles, the more it becomes possible to prevent light from being scattered in the scintillator layer, and a higher sharpness can be obtained. The phosphor particles may be dispersed in a binder. Examples of such a binder include polyurethane, vinyl chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, various types of synthesis. Examples thereof include rubber resins, phenol resins, epoxy resins, urea resins, melanin resins, phenoxy resins, silicon resins, acrylic resins, urea formamide resins, and the like. Among these, polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral, and nitrocellulose are preferably used. By using such a preferable binder, it becomes possible to increase the dispersibility of the phosphor and increase the filling rate of the phosphor, thereby contributing to the improvement of the graininess.

  The weight content of the phosphor dispersed in the binder is preferably 90 to 99%. The thickness of the first layer 301 is preferably 20 μm or more (particularly 50 μm or more) from the viewpoint of improving graininess, and is preferably 1 mm or less (particularly 300 μm or less) from the viewpoint of improving sharpness.

  In addition, since the fluorescent substance used in this embodiment is hygroscopic except for a part, it is preferably sealed so as not to be influenced by environmental moisture. For this reason, for example, by using the methods disclosed in JP-A-11-223890, JP-A-11-249243, JP-A-11-344598, and JP-A-2000-171597, the imaging panel 31 is used. Can be sealed entirely.

  A second layer 302 that converts electromagnetic waves (light) output from the first layer 301 into electrical energy is formed on the side of the first layer 301 opposite to the radiation irradiation surface side. The second layer 302 is provided with a diaphragm 302a, a transparent electrode 302b, a photoelectric conversion layer 302c, and a conductive layer 302d from the first layer 301 side. The transparent electrode 302b, the photoelectric conversion layer 302c, and the conductive layer 302d used here have the same configuration and role as the transparent electrode 12, the photoelectric conversion unit 14, and the counter electrode 13 in the bulk heterojunction photoelectric conversion element 10 described above. is there.

  The diaphragm 302a is for separating the first layer 301 from other layers, and for example, Oxi-nitride is used. The transparent electrode 302b can form a thin film using a method such as vapor deposition or sputtering. In addition, a pattern having a desired shape may be formed by photolithography, or when high pattern accuracy is not required (about 100 μm or more), a mask having a desired shape is used during vapor deposition or sputtering of the electrode material. A pattern may be formed. This transparent electrode desirably has a transmittance of more than 5%. Furthermore, although depending on the material, the film thickness is preferably 10 nm or more from the viewpoint of improving the uniformity of the film, and is preferably 1 μm or less (particularly 200 nm) from the viewpoint of shortening the production time.

  The photoelectric conversion layer 302c is formed of a photoelectric conversion unit having the bulk hetero layer shown in FIG. Of the P-type semiconductor material and the N-type semiconductor material in the bulk hetero layer, the semiconductor material having a low melting point is made richer than a mixing ratio that gives a preset photoelectric conversion rate. The photoelectric conversion layer 302 c generates electrons and holes by absorbing electromagnetic waves (light) output from the first layer 301. The holes generated here are collected in the conductive layer 302d, and the electrons are collected in the transparent electrode 302b. Note that in this structure, a hole conduction layer or an electron conduction layer may be formed between the transparent electrode 302b and the photoelectric conversion layer 302c, or between the conductive layer 302d and the photoelectric conversion layer 302c, but is indispensable. It is not a thing.

The conductive layer (counter electrode) 302d is made of, for example, chromium. In addition, a general metal electrode or the transparent electrode can be selected, but in order to obtain good characteristics, a metal, an alloy, an electrically conductive compound and a mixture thereof having a small work function (4.5 eV or less) are used. What is used as an electrode material is preferable. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, indium, lithium / aluminum mixture, all rare earths and the like. The conductive layer 302d can be generated using a method such as vapor deposition or sputtering using these electrode materials as raw materials. The sheet thickness of the conductive layer 302d is preferably 10 nm or more (particularly 50 nm or more) from the viewpoint of improving the uniformity of the film, and is preferably 1 μm or less (particularly 500 nm) from the viewpoint of shortening the production time.

  On the side opposite to the radiation irradiation surface side of the second layer 302, there is a third layer 303 for storing electric energy obtained in the second layer 302 and outputting a signal based on the stored electric energy. Is formed. The third layer 303 includes a capacitor 311 that stores the electric energy generated in the second layer 302 for each pixel, and a transistor 312 that is a switching element for outputting the stored electric energy as a signal. . Note that the third layer 303 is not limited to the one using a switching element. For example, the third layer 303 may be configured to generate and output a signal corresponding to the energy level of the stored electric energy.

  As the transistor 312, for example, a TFT (Thin Film Transistor) is used. This TFT may be an inorganic semiconductor type used in a liquid crystal display or the like, or an organic semiconductor, and is preferably a TFT formed on a plastic film. As the TFT formed on the plastic film, an amorphous silicon-based TFT is known. In addition, the FSA (Fluidic Self Assembly) technology developed by Alien Technology in the United States, that is, a microfabrication made of single crystal silicon. A TFT may be formed on a flexible plastic film by arranging CMOS (Nanoblocks) on an embossed plastic film. Furthermore, Science 283, 822 (1999) and Appl. Phys. A TFT using an organic semiconductor as described in documents such as Lett, 771488 (1998), Nature, 403, 521 (2000) may be used.

  As described above, the switching element used in this embodiment is preferably a TFT manufactured using the FSA technique and a TFT using an organic semiconductor, and a TFT using an organic semiconductor is particularly preferable. If a TFT is formed using this organic semiconductor, equipment such as a vacuum deposition apparatus is not required as in the case where a TFT is formed using silicon, and the TFT can be formed by utilizing printing technology or inkjet technology. Cost is low. Furthermore, since the processing temperature can be lowered, it can be formed into a plastic substrate shape that is weak against heat.

  In addition, a field effect transistor (FET) is particularly preferable among TFTs using an organic semiconductor, and specifically, an organic TFT having a structure shown in FIGS. 11A to 11C is preferable. In the organic TFT shown in FIG. 11A, a gate electrode, a gate insulating layer, source / drain electrodes, and an organic semiconductor layer are sequentially formed on a substrate. In the organic TFT shown in FIG. 11B, a gate electrode, a gate insulating layer, an organic semiconductor layer, and source / drain electrodes are sequentially formed on a substrate. In the organic TFT shown in FIG. 11C, a source / drain electrode, a gate insulating layer, and a gate electrode are sequentially formed on an organic semiconductor single crystal.

  The compound forming the organic semiconductor layer may be a single crystal material or an amorphous material, and may be a low molecule or a polymer, but particularly preferred are condensed aromatic carbonized carbons represented by pentacene, triphenylene, anthracene, etc. Examples thereof include single crystals of hydrogen compounds and π-conjugated polymers.

  The source electrode, the drain electrode, and the gate electrode may be metal, a conductive inorganic compound, or a conductive organic compound, but are preferably a conductive organic compound from the viewpoint of ease of manufacture. Typical examples include π-conjugated polymer compounds such as Lewis acids (eg, iron chloride, aluminum chloride, antimony bromide), halogens (eg, iodine and bromine), sulfonates (eg, polystyrene sulfonates). Examples thereof include those doped with sodium salt (PSS), potassium p-toluenesulfonate, etc., and specifically, a conductive polymer obtained by adding PSS to PEDOT is a typical example. Specific examples of the organic TFT include those shown in FIG.

  As shown in FIGS. 9 and 10, the transistor 312 that is a switching element stores electrical energy generated in the second layer 302 and is connected to a collecting electrode 310 that is one electrode of the capacitor 311. . The capacitor 311 stores the electrical energy generated in the second layer 302, and the stored electrical energy is read out by driving the transistor 312. That is, by driving the switching element, a signal for each pixel regarding the radiation image can be generated. In FIG. 10, the transistor 312 includes a gate electrode 312a, a source electrode (drain electrode) 312b, a drain electrode (source electrode) 312c, an organic semiconductor layer 312d, and an insulating layer 312e. .

  The fourth layer 304 is a substrate of the imaging panel 31. A substrate preferably used as the fourth layer 304 is a plastic film. Examples of such plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), Examples of the film include cellulose triacetate (TAC) and cellulose acetate propionate (CAP). By using such a plastic film, the weight can be reduced as compared with the case where a glass substrate is used, and the resistance to impact is improved.

  Furthermore, a plasticizer such as trioctyl phosphate or dibutyl phthalate may be added to these plastic films, or a known ultraviolet absorber such as benzotriazole or benzophenone may be added. In addition, a resin prepared by applying a so-called organic-inorganic polymer hybrid method in which a raw material of an inorganic polymer such as tetraethoxysilane is added and the molecular weight is increased by applying energy such as a chemical catalyst, heat, or light. It can also be used as a raw material.

  Further, on the side opposite to the surface on the third layer 303 side in the fourth layer 304, as the power supply unit 38, for example, a primary battery such as a manganese battery, a nickel-cadmium battery, a mercury battery, or a lead battery, a rechargeable secondary A battery may be provided. As a form of this battery, a flat form is preferable so that the radiation image detector can be thinned.

  In addition, the imaging panel 31 is provided with initialization transistors 315-1 to 315-n, for example, having drain electrodes connected to the signal lines 314-1 to 314-n (FIG. 9). The source electrodes of the transistors 315-1 to 315-n are grounded. The gate electrode is connected to the reset line 316.

  The scanning lines 313-1 to 313-m and the reset line 316 of the imaging panel 31 are connected to the scanning drive circuit 32. When the readout signal RS is supplied from the scanning drive circuit 32 to one of the scanning lines 313-1 to 313-m (p is any value of 1 to m), the scanning line 313 is supplied. The transistors 312- (p, 1) to 312- (p, n) connected to −p are turned on, and the electricity stored in the capacitors 311− (p, 1) to 311− (p, n) Energy is read out to the signal lines 314-1 to 314-n, respectively. The signal lines 314-1 to 314-n are connected to the signal converters 331-1 to 331-n of the signal selection circuit 33. In the signal converters 331-1 to 331-n, the signal lines 314-1 to 314 are connected. Voltage signals SV-1 to SV-n proportional to the amount of electric energy read on -n are generated. The voltage signals SV-1 to SV-n output from the signal converters 331-1 to 331 -n are supplied to the register 332.

  In the register 332, the supplied voltage signal is sequentially selected and converted into a digital image signal for one scanning line (for example, 12 bits to 14 bits) by the A / D converter 333. The control circuit 34 supplies the readout signal RS to each of the scanning lines 313-1 to 313-m via the scanning drive circuit 32 to perform image scanning, captures a digital image signal for each scanning line, and obtains a radiographic image. The image signal is generated. Note that the reset signal RT is supplied from the scanning drive circuit 32 to the reset line 316 to turn on the transistors 315-1 to 315-n, and the readout signal RS is supplied to the scanning lines 313-1 to 313-m. By turning on the transistors 312- (1,1) to 312- (m, n), the electric energy stored in the capacitors 311- (1,1) to 311- (m, n) is converted into the transistor 312- 1 to 312-n and the imaging panel 31 is initialized.

  A memory unit 35 and an operation unit 36 are connected to the control circuit 34, and the operation of the radiation image detector 3 is controlled based on an operation signal PS from the operation unit 36. The operation unit 36 is provided with a plurality of switches. Based on the operation signal PS corresponding to the switch operation from the operation unit 36, the imaging panel 31 is initialized and the image signal of the radiation image is generated. The generation of the image signal of the radiation image may be performed when a radiation irradiation end signal is supplied from the radiation generator 4 via the connector 39. Further, the control circuit 34 performs processing for storing the generated image signal in the memory unit 35 and the like.

Here, as shown in FIG. 8, the radiographic image detector 3 is provided with a power supply unit 38 and a memory unit 35 for storing an image signal of the radiographic image, and the radiographic image detector 3 is detachable via a connector 39. By doing so, a system capable of carrying the radiation image detector 3 can be constructed. Further, if the memory unit 35 is configured to be detachable using a non-volatile memory, the image signal can be obtained only by mounting the memory unit 35 on the image processing unit 51 without connecting the radiation image detector 3 and the image processing unit 51. Can be supplied to the image processing unit 51, so that radiographic images can be easily captured and processed, and operability can be improved. When the radiological image detector 3 is used as a stationary type, by supplying power and reading out an image signal through the connector 39, the radiographic image can be read without providing the memory unit 35 and the power source unit 38. Of course, an image signal can be obtained.

  In the radiation image detector 3 in the present embodiment, a semiconductor material having a low melting point out of the P-type semiconductor material and the N-type semiconductor material in the bulk hetero layer is richer than a mixture ratio that gives a preset photoelectric conversion rate. Therefore, since the semiconductor material having a low melting point is compensated for by the crystallinity being destroyed by the annealing treatment, even if the crystallinity of the bulk hetero layer is deteriorated by this annealing treatment, the deterioration of the photoelectric conversion efficiency is suppressed.

  In this embodiment, the fourth layer 304 serving as a substrate is made of resin, so that the weight can be reduced as compared with a conventional radiation image detector using a glass substrate. In addition, since the fourth layer 304 is made of resin, the third layer 303 formed on the fourth layer 304 is formed of a divided silicon stacked structure element or an organic semiconductor. Therefore, unlike the conventional radiographic image detector using a glass substrate, it is not necessary to use an expensive and special manufacturing apparatus for forming a thin film transistor mainly composed of silicon on the glass substrate. Can be manufactured at low cost.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

It is sectional drawing which shows an example of the bulk heterojunction photoelectric conversion element in 1st Embodiment. 6 is a diagram showing a relationship between a mixing ratio of P3HT and crystallinity in an element A. FIG. 6 is a diagram showing the relationship between the annealing temperature and crystallinity in element A. FIG. 6 is a diagram showing a relationship between the mixing ratio of P3OT and the crystallinity in the element B. FIG. FIG. 5 is a diagram showing the relationship between the annealing temperature and crystallinity in element B. It is a figure which shows the structure of the optical sensor array in 2nd Embodiment. It is a block diagram which shows the image detection system using the radiographic image detector in 3rd Embodiment. It is a partially broken perspective view which shows an example of the structure of the radiographic image detector in 3rd Embodiment. It is a circuit diagram which shows the circuit structure of the imaging panel in 3rd Embodiment. The partial cross section figure (1 pixel) of the imaging panel in 3rd Embodiment is shown. It is a perspective view which shows the structure of organic TFT. It is a figure which shows the specific example of organic TFT.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Radiation image detector 10 Bulk heterojunction photoelectric conversion element 12, 22, 302b Transparent electrode 13, 23 Counter electrode 14, 24 Photoelectric conversion part 20 Photosensor array 31 Imaging panel (photosensor array)
302c Photoelectric conversion layer 303d Conductive layer (counter electrode)

Claims (10)

In a bulk heterojunction photoelectric conversion element including a bulk hetero layer in which a P-type semiconductor material and an N-type semiconductor material are mixed,
A bulk heterojunction photoelectric conversion element characterized in that, among the P-type semiconductor material and the N-type semiconductor material, a semiconductor material having a low melting point is richer than a mixing ratio that gives a preset photoelectric conversion rate. The bulk heterojunction photoelectric conversion element according to claim 1, wherein the semiconductor material having a low melting point is a P-type semiconductor material. The bulk heterojunction photoelectric conversion element according to any one of claims 1 and 2, wherein the P-type semiconductor material is poly-3-hexylthiophene or poly-3-octylthiophene. The bulk heterojunction photoelectric conversion device according to any one of claims 1 to 3, wherein the N-type semiconductor material is a fullerene derivative. The P-type semiconductor material is poly-3-hexylthiophene;
The N-type semiconductor material is a fullerene derivative;
The bulk heterojunction photoelectric conversion element according to claim 1, wherein the amount of the P-type semiconductor material to be rich is 15% or less by weight. The P-type semiconductor material is poly-3-octylthiophene;
The N-type semiconductor material is a fullerene derivative;
The bulk heterojunction photoelectric conversion element according to claim 1, wherein the amount of the P-type semiconductor material to be enriched is 20% or less by weight. The bulk heterojunction photoelectric conversion element according to any one of claims 1 to 6, wherein the bulk hetero layer is annealed. The bulk heterojunction photoelectric conversion element according to claim 7, wherein the annealing temperature is substantially the melting point of a semiconductor material having a low melting point. An optical sensor array comprising the bulk heterojunction photoelectric conversion elements according to any one of claims 1 to 8 arranged in an array. A first layer that emits light according to the intensity of incident radiation, a second layer that converts light energy output from the first layer into electrical energy, and accumulation and accumulation of electrical energy obtained in the second layer A radiation image detector comprising: a third layer for outputting a signal based on the generated electrical energy;
The radiation image detector, wherein the second layer includes a bulk hetero layer of the bulk heterojunction photoelectric conversion device according to any one of claims 1 to 8.

Images