CN105957968A - Method for improving photoelectric conversion efficiency of silicon-based photovoltaic device - Google Patents

Abstract

The invention discloses a method for improving the photoelectric conversion efficiency of a silicon-based photovoltaic device, which is characterized in that it comprises preparation of silver nanosheets, wet etching of silicon nanowire arrays, silicon nanowires-silver nanosheets-poly(3,4-sub- Ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device assembly, etc. The synthesis/assembly method of the invention is simple, clear in principle and obvious in effect. Adopting the method of the present invention utilizes nano-noble metal plasmons to generate thermal electron injection mechanism, so that the current density and light absorption range of silicon-based photovoltaic devices are increased, and the photoelectric conversion efficiency in the near-infrared region is significantly improved, which is beneficial to realizing a wide solar spectrum. The (full) spectral response, absorption and utilization play an important role. The invention is a very promising method for widening the spectrum of solar energy utilization and improving the photoelectric conversion efficiency, and has wide energy and industrial applications.

Description

A method for improving photoelectric conversion efficiency of silicon-based photovoltaic devices

technical field

The invention belongs to the technical field of solar photoelectricity, and in particular relates to a method for improving the photoelectric conversion efficiency of a silicon-based photovoltaic device by using the thermal electron injection effect generated by nano-noble metal plasmons.

Background technique

China National Scientific Think Tank Decision Consulting Series "Solar Cell Development Status and Performance Improvement Research" (Science Press, 2014 first edition, 1-7 pages) pointed out that the use of solar energy is the solution to the current severe energy and environmental problems It is one of the effective ways, and it is also a focus of research by scientists from all over the world. Among various forms of energy conversion, electric energy has the advantages of being clean and easy to use, easy to store and transport, so photoelectric conversion has become a major solar energy utilization method. The basis of photoelectric conversion of solar cells is the photovoltaic effect of semiconductor materials/semiconductor-like materials. Currently, widely studied solar cells include elemental semiconductor solar cells (single crystal silicon, polycrystalline silicon, silicon thin films), compound semiconductor solar cells (III-V compound , CIGS thin film, CdTe thin film), dye-sensitized solar cells, organic polymer solar cells, and next-generation ultra-high-efficiency solar cells such as perovskite solar cells and quantum dot solar cells. The efficient utilization of solar energy can be achieved by improving the light absorption range and conversion efficiency. However, most photovoltaic devices currently absorb visible light, and the near-infrared light, which accounts for 52% of sunlight, has not been efficiently utilized. "Research on the Development Status and Performance Improvement of Solar Cells" (Science Press, 2014 first edition, pages 169-172) pointed out that the development of high-efficiency, low-cost third-generation silicon-based solar cells has become one of the frontier topics of concern. First, this requires the use of new materials, new technologies, and new structures that are different from conventional ones. One of the main solutions is to make silicon-based materials respond effectively to both long-wavelength and short-wavelength light, that is, to realize the solar spectrum wide (full) spectral response. Because of this, enhancing the absorption and utilization of sunlight in the near-infrared region has become a key scientific issue, which puts forward specific requirements for the design and mechanism research of device types. If the conversion efficiency in the near-infrared region can be improved, it can make solar energy The battery efficiency is further improved, the utilization efficiency of solar energy is further increased, and the related production capacity and benefits are more prominent. "Research on the Development Status and Performance Improvement of Solar Cells" (Science Press, first edition in 2014, pages 172-180) pointed out that in current research, the design of silicon-based photovoltaic devices for broad spectral response mainly includes multilayer/multilayer The design of junction cells, and the use of new materials such as silicon quantum dots. The preparation of multi-layer/multi-junction cells is cumbersome and requires extremely high process precision; although the use of new materials such as silicon quantum dots can obtain a wide spectral response, there is no expansion and innovation in the mechanism of action, and it cannot break through the bottleneck of photovoltaic device efficiency.

According to "Science Bulletin" (2011, Issue 56, pp. 2631-2661) "Regulation and Utilization of Surface Plasmon Resonance of Metal Nanostructures", it is pointed out that noble metal nanoparticles have intrinsic plasmon effects, and their resonance absorbs light. It has a wide adjustable range, and has outstanding performance in optical absorption enhancement, photothermal effect, and hot electron excitation, and can introduce photons into the nanometer scale. During the energy release process of plasmons, electron-hole pairs with higher energy than the background thermal distribution will be generated. These hot carriers with higher energy have a good prospect for photodynamic applications. Plasmons have already had some good applications in optics, such as in photocatalysis, photodetection, and photoelectric conversion. At present, the use of plasmonic elements in photoelectric conversion is mainly based on the noble metal array structure, which has been used to achieve a wide (full) spectral response to the solar spectrum. However, the noble metal array structure has high requirements for equipment and technology. It cannot be prepared simply and in large quantities, and the cost is also very high. Compared with the noble metal array structure, noble metal nanoparticles have extremely low requirements on equipment technology, are easy to synthesize in large quantities, and have a wide range of adjustments. However, in the field of photovoltaic devices, the application and mechanism of plasmons of noble metal nanoparticles have not yet been obtained. good research.

Based on this, there is an urgent need to develop a simple and effective method, especially for sunlight in the near-infrared region, using the nano-noble metal plasmon effect to assemble photovoltaic devices with more broad-spectrum absorption and response, so that the solar energy utilization efficiency can be improved and improved. .

Contents of the invention

The purpose of the present invention is to propose a method for improving the photoelectric conversion efficiency of silicon-based photovoltaic devices, so that the thermal electrons generated by plasmons in the near-infrared region of silver nanosheets can be continuously injected into the silicon-based photovoltaic devices under the action of light. In the main body of transmission, to increase the light absorption range of photovoltaic devices and improve the corresponding conversion efficiency.

The method for improving the photoelectric conversion efficiency of silicon-based photovoltaic devices in the present invention is characterized in that:

According to the mixed solution composed of 0.5mL 25-100mmol/L silver nitrate aqueous solution, 5mL 50-150mmol/L sodium citrate aqueous solution and 0.5-2mL hydrogen peroxide with a mass concentration of 30% in 250mL water, add it under stirring at room temperature In 2.5mL of 50-200mmol/L sodium borohydride aqueous solution in an ice-bath environment, react for 5-10 minutes to obtain silver nano-triangular sheets; after centrifuging and washing the obtained silver nano-sheets with water three times, disperse them in 2mL of water to form Silver nanosheet aqueous dispersion;

After using oxygen plasma to clean the organic matter on the surface of the silicon wafer master, then use a hydrofluoric acid aqueous solution with a mass concentration of 3-10% to clean the surface of the silicon wafer master for 1-5 minutes; the silicon wafer master after the above pretreatment Immerse in an aqueous solution containing 2.5-10mmol/L silver nitrate and 2.4-4.8mol/L hydrofluoric acid, and react under uniform stirring to form a layer of silver particles with a size of 10-300nm on the surface of the silicon chip master; Immerse the chip in an aqueous solution containing 3-6mol/L hydrogen peroxide and 2.4-4.8mol/L hydrofluoric acid for wet etching, and let it stand for 2-20 minutes; first use dilute nitric acid with a mass concentration of 30-50%, and then Use hydrofluoric acid with a mass concentration of 3-10% to clean the remaining silver particles and the oxide layer on the surface of the array to obtain a silicon nanowire array; clean the obtained silicon nanowire array with argon plasma to control the plasma The working voltage of the cleaning instrument is 0.5-1.5kV, and the air pressure in the working chamber of the instrument is 10-10 ² Pa. Clean until the surface silicon-hydrogen bond cannot be detected by infrared spectroscopy;

Then, the previously prepared silver nanosheet water dispersion liquid is dropped on the above-mentioned silicon nanowire array after cleaning and removing the silicon-hydrogen bond to completely cover the silicon nanowire array, and then the volume ratio concentration is 60% poly(3,4 -Ethylenedioxythiophene)-poly(styrenesulfonic ^acid ) ethanol solution is dropped on its outer surface until it is completely covered; and then coated with poly(3,4 -ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution of 8Ω/sq indium tin oxide transparent glass is covered on it, so that the poly(3,4) on the indium tin oxide transparent glass and silicon nanowire array -ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solutions are in contact with each other, and indium tin oxide transparent glass is used as the front electrode; silver glue is coated on the back of the silicon wafer as the back electrode.

The silver nitrate aqueous solution concentration used in the preparation of silver nanosheets is preferably 50mmol/L, the sodium citrate aqueous solution concentration is preferably 75mmol/L, and the volume of hydrogen peroxide with a mass concentration of 30% is preferably 1mL, and the sodium borohydride aqueous solution concentration is preferably 1mL. Preferably it is 100mmol/L; the reaction time for preparing silver nanosheets is preferably 5 minutes.

The silicon wafer master is preferably an N-type (100) silicon wafer of 1 to 10 Ω·cm;

The cleaning time of the silicon wafer master plate using oxygen plasma is preferably 1 minute;

The preferred mass concentration of hydrofluoric acid used for cleaning the pre-treated silicon wafer master is 5%, and the cleaning is performed for 1 minute.

The concentration of the silver nitrate aqueous solution used in the preparation of the silicon nanowire array is preferably 5 mmol/L, the concentration of the hydrofluoric acid aqueous solution is preferably 4.8 mol/L, and the concentration of the hydrogen peroxide aqueous solution is preferably 4.5 mol/L;

The hydrogen peroxide-hydrofluoric acid etching time for preparing the silicon nanowire array is preferably 3 minutes, preferably controlled so that the length of the obtained silicon nanowire is ² μm, and the distance between adjacent nanowires is 50-500 nm; The amount of silver nanosheets added to the silicon nanowire array is preferably 200 nmol.

The cleaning after the wet etching is preferably firstly cleaned with 30% dilute nitric acid and then with 5% hydrofluoric acid for 1 minute respectively.

The silicon nanowire array is cleaned with argon plasma, and the operating voltage of the plasma cleaning instrument is preferably 1 kV, the pressure in the working chamber of the instrument is preferably 40 Pa, and the time is preferably 30 minutes.

The dripping amount of the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution added to the silicon nanowire array is preferably 20 μL/cm ² ; the operation sequence is preferably, first Silver nanosheets are added to the silicon nanowire array, and then poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution is added to make the silver nanosheets directly contact the silicon nanowires, and between the interfaces of inorganic-organic heterojunctions.

The mechanism of the method for improving the photoelectric conversion efficiency of silicon-based photovoltaic devices in the present invention is: silver nanosheets generate plasmons under the action of light, mainly in the near-infrared region, and the energy of plasmons is released by high-energy electron-hole pairs. form, that is, hot carriers. When silver nanosheets are in direct contact with silicon nanowire arrays, a Schottky barrier will be formed at the interface. Since the hot electrons generated by silver nanosheet plasmons have relatively high energy, they can cross the Schottky barrier or tunnel through Potential barrier, continuously injected into the conduction band of silicon, and original electron flow generated by photoexcitation in silicon-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction Convergence, the effect of enhancing the carrier density is achieved; in addition, the hot holes will flow to the highest electron-occupied orbital of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), forming an effective, A circuit that can increase the current density. The final performance is the improvement of photoelectric conversion efficiency and the increase of light absorption range.

Using the method of the invention to prepare photovoltaic devices with enhanced photoelectric efficiency and increased light absorption range in the near-infrared region, the addition and control of silver nanosheets that can generate plasmons in the near-infrared region is one of the keys to success.

According to the method of the present invention, the conversion efficiency of silicon-based photovoltaic devices in the near-infrared region can be improved and the overall light absorption range can be increased, which has the following advantages:

1. Compared with the existing technology related to photovoltaic devices, the silver nanosheet plasmon hot electron injection method adopted in the present invention is simple and easy, can be synthesized in large quantities, and the position of the plasmon resonant peak is adjustable. The intervention is simple and controllable, which is conducive to the popularization of the future application of this method.

2. For the efficiency improvement and broad-spectrum absorption of photovoltaic devices, the silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic The heterojunction device applies the hot carriers generated by the plasmon effect of noble metal nanoparticles to silicon-based photovoltaic devices, which improves the efficiency in the near-infrared region and absorbs a broader spectrum, which increases by 59% at 800nm.

The invention has the advantages of simple synthesis/assembly method, clear mechanism and obvious effect. After adopting the method of the invention, the current density of silicon-based photovoltaic devices is increased, the light absorption range is increased, and the photoelectric conversion efficiency in the near-infrared region is significantly improved.

Since the present invention adopts the method of plasmonic hot electron injection in silicon-based photovoltaic devices, there is no hot electron injection in this type of silicon-based photovoltaic devices that adopts plasmonic element effect to make conversion Reports on ways to improve efficiency. In the current technology, nano-noble metal arrays or structural plasmonic elements are used to increase the absorption of the spectral range. Compared with the synthesis/assembly method of the present invention, the synthesis/assembly method is simple, the principle is clear, and the effect is obvious. This technology makes the current density of photovoltaic devices The increase, the absorption range, and the photoelectric conversion efficiency in the near-infrared region have been significantly improved, which play an important role in realizing the wide (full) spectral response, absorption and utilization of the solar spectrum.

Description of drawings

Fig. 1 is the ordinary transmission electron microscope (TEM) photograph of gained silver nanoplate in the embodiment of the present invention 1;

Fig. 2 is the ultraviolet-visible extinction spectrum (UV-vis) curve of silver nanosheet in embodiment 1.

Fig. 3 is the scanning electron microscope (SEM) photograph that the silicon nanowire obtained in embodiment 1 is covered with silver nanoplate;

Fig. 4 is the SEM photo of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) covered with silicon nanowires obtained in Example 1;

Fig. 5 is a current-voltage characteristic curve of a silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device.

Fig. 6 is the quantum efficiency curve of silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device.

Fig. 7 is the current-voltage characteristic curve of silicon nanowire-silver nanosheet-reduced graphene oxide Schottky junction device obtained in embodiment 2;

8 is the quantum efficiency curve of the silicon nanowire-silver nanosheet-reduced graphene oxide Schottky junction device obtained in Example 2.

Figure 9 is the current of the flexible thin silicon silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device obtained in Example 3 - voltage characteristic curve;

Fig. 10 is a photo of flexible thin silicon nanowires obtained in Example 3 coated on indium tin oxide transparent plastic.

detailed description

Example 1:

Add 0.5mL of 50mmol/L silver nitrate aqueous solution, 5mL of 75mmol/L sodium citrate aqueous solution and 1mL of 30% hydrogen peroxide to 250mL of water, and add 2.5mL of 100mmol/L in an ice bath environment while stirring at room temperature Sodium borohydride aqueous solution was reacted for 5 minutes to obtain silver nano-triangular sheets; after the obtained silver nano-sheets were centrifuged and washed three times with water, they were dispersed in 2 mL of water to form an aqueous dispersion of silver nano-sheets;

Fig. 1 is the ordinary transmission electron microscope (TEM) photograph of silver nanosheet obtained in the present embodiment 1; Fig. 2 is the ultraviolet-visible extinction spectrum (UV-vis) curve of silver nanosheet. It can be seen from Figure 1 that the size of the silver nanosheets is 50nm and the shape is a triangular sheet; it can be seen from Figure 2 that the silver nanosheets have spectral absorption in the ultraviolet-visible-near-infrared band, and have obvious light absorption in the near-infrared region.

If instead of using 0.5mL 25mmol/L silver nitrate aqueous solution, 5mL 50mmol/L sodium citrate aqueous solution and 0.5mL mass concentration 30% hydrogen peroxide, and adding 2.5mL 50mmol/L sodium borohydride aqueous solution, reaction 10 Minutes, silver nanosheets can also be obtained.

If you use 0.5mL 100mmol/L silver nitrate aqueous solution, 5mL 150mmol/L sodium citrate aqueous solution, 2mL hydrogen peroxide with a mass concentration of 30%, and 2.5mL 200mmol/L sodium borohydride aqueous solution, and react for 5 minutes, you can also to obtain silver nanosheets.

Clean the master plate of silicon wafer with oxygen plasma for 1 minute, then clean the surface with 5% hydrofluoric acid aqueous solution with mass concentration for 1 minute, and immerse the master plate of silicon wafer after the cleaning treatment in a solution containing 5 mmol/L silver nitrate and 4.8 mol/L hydrogen In an aqueous solution of hydrofluoric acid, react at room temperature for 1 minute. Rinse the obtained silicon chip with water three times, then immerse the above-mentioned silicon chip in an aqueous solution containing 4.5mol/L hydrogen peroxide and 4.8mol/L hydrofluoric acid, let it stand for 3 minutes, rinse it with water three times, and then wash it with a mass concentration of 30 % nitric acid and 5% hydrofluoric acid for 1 min respectively. Dry the obtained silicon nanowire array with nitrogen gas, and then clean the silicon nanowire array with argon plasma for 30 minutes. Whether the surface silicon-hydrogen bonds have been completely removed can be detected by infrared spectroscopy.

FIG. 3 is a scanning electron microscope (SEM) photo of silicon nanowires coated with silver nanosheets obtained in this example. It can be seen from Figure 3 that the silicon nanowires are arranged vertically and neatly, with a length of 3 μm. The same effect can also be obtained if the surface of the silicon wafer master is cleaned for 5 minutes with a mass concentration of 5% hydrofluoric acid aqueous solution; if the silicon wafer master is immersed in an aqueous solution containing 2.5mmol/L silver nitrate and 2.4mol/L hydrofluoric acid Silver particles can also be formed on the surface in an aqueous solution of 10mmol/L silver nitrate and 4.8mol/L hydrofluoric acid; if an aqueous solution containing 3mol/L hydrogen peroxide and 2.4mol/L hydrofluoric acid or containing An aqueous solution of 6mol/L hydrogen peroxide and 4.8mol/L hydrofluoric acid can also obtain silicon nanowire arrays. Depending on the length of the wet etching reaction, the length of the obtained silicon nanowire arrays is also different. After 20 minutes of reaction, a silicon nanowire array with a length of about 20 μm was obtained. In the control plasma cleaning, the plasma energy is weak when the working voltage of the instrument is 0.5kV and the chamber pressure is 100Pa; the plasma energy is strong when the control working voltage is 1.5kV and the chamber pressure is 10Pa.

Drop the previously prepared silver nanosheet water dispersion on the above-mentioned silicon nanowire array after cleaning and removing the silicon-hydrogen bond to completely cover the silicon nanowire array, and then add poly(3,4- The ethanol solution of ethylenedioxythiophene)-poly(styrene sulfonic acid) is dropped on its outer surface until it is completely covered, the amount of silver nanosheets added is 200nmol/cm ² , poly(3,4-ethylenedioxythiophene )-poly(styrenesulfonic acid) ethanol solution was added in an amount of 20 μL/cm ² .

Figure 4 shows the silicon nanowires coated with poly(3,4-ethylenedioxythiophene) obtained after dropping poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) in this example. - SEM scanning photograph of silicon nanowire arrays of poly(styrene sulfonic acid) (PEDOT:PSS). It can be seen from FIG. 4 that the silicon nanowires are coated with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), which has covered the surface of the silicon nanowire array.

Then, 8 Ω/sq indium tin oxide transparent glass coated with 0.5 μL/cm ² of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution was coated on the above-mentioned drops of silver nanoparticles. On the silicon nanowire array of sheet water dispersion and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution, making indium tin oxide transparent glass and poly( The ethanol solutions of 3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) are in contact with each other, and the indium tin oxide transparent glass is used as the front electrode; the silver glue is coated on the back of the silicon wafer as the back electrode.

The drop amount of silver nanosheets is 50-500nmol/cm ² . When the drop amount is 50nmol/cm ² , the silver nanosheets loaded on the silicon nanowire array are relatively thin. When the drop amount is 500nmol/cm ² , the silicon nanowires The silver nanosheets loaded on the array are denser. On the silicon nanowire array, the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution can be added in an amount of 5-50 μL/cm ² , and the dropping amount is 5 μL/cm ² The coverage is thinner when the dripping amount is 50μL/cm ² and the coverage is thicker. The same effect can be achieved by coating indium tin oxide transparent glass with 5 μL/cm ² poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution.

The current-voltage characteristic curve and quantum efficiency curve of silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device were tested.

Figure 5 is the current-voltage characteristic curve of silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device; Figure 6 is the silicon Quantum efficiency curves of nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction devices. It can be seen from Figure 5 that the open circuit voltage and short circuit current of the inorganic-organic heterojunction device are significantly increased when the silver nanosheets are intervened. It can be seen from Figure 6 that the inorganic-organic heterojunction device is mainly responsive to light in the 400-1000nm band, and the light absorption efficiency of the device in the 600-1000nm band is significantly increased when silver nanosheets are intervened.

Table 1 below shows the parameters related to the photoelectric conversion efficiency of the silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) heterojunction device:

Table 1 Relevant parameters of photoelectric conversion efficiency of silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) heterojunction device

After adding silver nanosheets, the current-voltage characteristic curve (see Figure 5), quantum efficiency curve (see Figure 6) and related parameters (see Table 1) of inorganic-organic heterojunction devices intervened by/without silver nanosheets It can be seen that the light absorption range of the inorganic-organic heterojunction photovoltaic device intervened by silver nanosheets is increased, the current density is increased, the open circuit voltage is improved, and the photoelectric conversion efficiency is significantly improved.

Example 2:

Utilizing the characteristics of hot electron injection of silver nanosheet plasma units, it can also be applied to other silicon-based photovoltaic devices, and the light absorption range of photovoltaic devices can also be increased and the photoelectric conversion efficiency can be improved.

The synthesis of silver nanosheets and the preparation of silicon nanowires are the same as in Example 1, and the time taken for wet etching is 20 minutes.

Reduced graphene oxide (rGO) can be obtained by reducing graphene oxide prepared by the Hummol/Lers method. Add 30 mg of graphene oxide to 30 mL of water, then add 30 mg of ascorbic acid, and react at 80°C for 3 hours. Then, the obtained large pieces of reduced graphene oxide were ultrasonicated for 10 minutes*3 times with a cell ultrasonic disruptor, and dispersed into 30 mL of water.

An aqueous dispersion of silver nanosheets (200nmol/cm ² ) was dropped on the silicon nanowires, and then a 0.15 mL/cm ² redox graphene suspension was dropped on the silicon nanowires surrounded by insulating materials. Silver paste was coated on the graphene oxide on top of the insulating material as the front electrode. Apply silver glue on the back of the silicon wafer as the back electrode. The current-voltage characteristic curve and quantum efficiency curve of the silicon nanowire-silver nanosheet-reduced graphene oxide Schottky junction device were tested.

Table 2 shows the parameters related to the photoelectric conversion efficiency of the silicon nanowire-silver nanosheet-reduced graphene oxide Schottky junction device:

Table 2 Relevant parameters of photoelectric conversion efficiency of silicon nanowire-silver nanosheet-reduced graphene oxide Schottky junction device

V _oc (V) J _sc (mA·cm ^-2 ) FF η(%) Silicon Nanowires-Reduced Graphene Oxide 0.25 15.11 17.7 0.0007 Silicon nanowires-silver nanosheets-reduced graphene oxide 0.33 88.28 20.8 0.0060

Figure 7 shows the current-voltage characteristic curve of the silicon nanowire-silver nanosheet-reduced graphene oxide Schottky junction device; Figure 8 is its quantum efficiency curve. It can be seen from FIG. 7 that when silver nanosheets are intervened, the short-circuit current of the Schottky junction device is significantly increased, and the open-circuit voltage is also increased. It can be seen from Figure 8 that the Schottky junction device mainly responds to light in the 600-1100nm band, and the light absorption efficiency of the device in the 700-1000nm band increases significantly when silver nanosheets are intervened.

After adding silver nanosheets, the current-voltage characteristic curve (see Figure 7), quantum efficiency curve (see Figure 8) and related parameters of the silicon nanowire-graphene oxide Schottky junction device intervened by/without silver nanosheets (See Table 2) It can be seen that the light absorption range of the silicon-based Schottky junction device using the thermal electron injection mechanism increases, the current density increases significantly, the open circuit voltage also increases, and the photoelectric conversion efficiency increases significantly.

Example 3:

In silicon-based photovoltaic devices, silicon wafer masters can be thinned to obtain mechanically flexible thin silicon wafers, and silicon nanowire arrays can be obtained on the basis of thin silicon wafers, flexible silicon-based photovoltaic devices can be obtained, and The light absorption range is increased and the photoelectric conversion efficiency is improved by using the silver nanosheets.

The synthesis of silver nanosheets and the preparation of silicon nanowires are the same as in Example 1, with double-sided etching. Thinning is performed on the selected silicon wafer master to obtain silicon wafers. A 100 μm-thick N-type (100) silicon wafer (2-5Ω·cm) is selected, and an inductively coupled plasma etching machine is used for etching and thinning process. Clean the silicon wafer master with acetone, isopropanol, and water, hang coat it on the silicon wafer with PMMOL/LA (1500rpm, 30s), soft bake at 180°C, use an inductively coupled plasma etching machine, first use oxygen plasma Clean the surface, and then etch with mixed gas (140repeats, Dep: 4s, C ₄ H ₈ 100sccm, SF ₆ 1sccm; Etch: 7s, C ₄ H ₈ 1sccm, SF ₆ 100sccm), to obtain 10μm thick silicon flakes, and then use Oxygen plasma cleaning followed by acetone cleaning.

The aqueous dispersion of silver nanosheets (200nmol/cm ² ) and the ethanol solution (20μL/cm ² ) of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) with a volume concentration of 60% were dropped On one side of the aforementioned thin silicon nanowires. Then cover the surface of the thin silicon nanowire on the indium tin oxide transparent plastic (30Ω/sq) coated with a small amount of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) ethanol solution, and the back The side silicon nanowires are connected with silver glue as the back electrode, and the positive electrode is the conductive surface of indium tin oxide transparent plastic. The current-voltage characteristic curve of the flexible thin silicon silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device was tested.

Figure 9 is the flexible thin silicon silicon nanowire-silver nanosheet-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) inorganic-organic heterojunction device obtained in Example 3. Current-voltage characteristic curve; As can be seen from Figure 9, the flexible photovoltaic device using the thermal electron injection mechanism has a relatively good photoelectric conversion efficiency, and can still maintain a good open circuit voltage and short circuit current after being bent 50 times. Fig. 10 is a photo of flexible thin silicon silicon nanowires covered on indium tin oxide transparent plastic; it can be seen from Fig. 10 that a flexible photovoltaic device using a thermal electron injection mechanism can be obtained through Example 3, which has relatively good mechanical flexibility.

The results of the above analysis and characterization prove that the result obtained in this example is the application of the hot electron injection enhancement effect of plasmons in silicon-based photovoltaic devices, which is a very important type of solar energy utilization spectrum broadening and photoelectric conversion efficiency improvement with great application prospects. methods and devices.

Since the present invention adopts the method of plasmonic hot electron injection in silicon-based photovoltaic devices, there is no such hot electron injection of plasmonic element effect in such silicon-based photovoltaic devices in the prior art to improve conversion efficiency In the current technology, there are nano-noble metal arrays or structural plasmonic elements to increase the absorption of the spectral range. In comparison, the synthesis/assembly method of the present invention is simple, the principle is clear, and the effect is obvious. This technology makes photovoltaic devices The current density increases, the absorption range increases, and the photoelectric conversion efficiency in the near-infrared region is significantly improved, which plays an important role in realizing the wide (full) spectral response, absorption and utilization of the solar spectrum.

Claims (8)

1. the method improving silicon-based photovoltaic device photoelectric conversion efficiency, it is characterised in that:

According to water-soluble by the sodium citrate of the silver nitrate aqueous solution of 0.5mL 25-100mmol/L, 5mL 50-150mmol/L The hydrogen peroxide of liquid and 0.5-2mL mass concentration 30% adds the mixed liquor of composition in 250mL water, under stirring at room temperature Add and be in the sodium borohydride aqueous solution of the 2.5mL 50-200mmol/L in ice bath environment, react 5-10 minute, To silver nanoparticle triangular plate；After obtained Nano silver piece water eccentric cleaning three times, it is dispersed in 2mL water, forms silver Nanometer sheet aqueous dispersions；

After using oxygen plasma to wash the Organic substance of silicon chip master surfaces, then with the Fluohydric acid. water of mass concentration 3-10% Solution cleaning silicon chip master surfaces 1-5 minute；To immerse containing 2.5-10mmol/L through above-mentioned pretreated silicon chip mother matrix In the aqueous solution of silver nitrate and 2.4-4.8mol/L Fluohydric acid., react under uniform stirring to silicon chip master surfaces formation one layer The Argent grain of a size of 10-300nm；Again above-mentioned silicon chip is immersed containing 3-6mol/L hydrogen peroxide and 2.4-4.8mol/L hydrogen Fluorine aqueous acid carries out wet etching, stands 2-20 minute；First with the dust technology of mass concentration 30-50%, use again The Fluohydric acid. of mass concentration 3-10% washes Argent grain and the oxide layer on surface of remaining in array, obtains silicon nanometer Linear array；Obtained silicon nanowire array argon plasma is cleaned, controls the work of plasma cleaning apparatus Voltage is 10-10 at 0.5-1.5kV, instrument working chamber internal gas pressure²Under the conditions of Pa, cleaning to infrared spectrum inspection does not measures table Face si-h bond；

Nano silver piece aqueous dispersions the most prepared above is dropped in the silicon nanowires after above-mentioned cleaned removing si-h bond Array is up to completely covered silicon nanowire array, then poly-(3, the 4-Ethylenedioxy Thiophene) that volume by volume concentration is 60%-poly- The ethanol solution of (styrene sulfonic acid) drops in its outer surface to being completely covered；0.5-5 μ L/cm will be scribbled again²Volume by volume concentration It is the 8 Ω/sq indium tin oxide transparent glass of poly-(3,4-Ethylenedioxy Thiophene)-poly-(styrene sulfonic acid) ethanol solution of 60% Cover thereon, make poly-(3, the 4-Ethylenedioxy Thiophene)-poly-(styrene on indium tin oxide transparent glass and silicon nanowire array Sulfonic acid) ethanol solution contacts with each other, using indium tin oxide transparent glass as front electrode；Elargol is coated in silicon chip back as Back electrode.

2. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described preparation The silver nitrate aqueous solution concentration that Nano silver piece is used is 50mmol/L, and sodium citrate aqueous solution concentration is 75mmol/L, The volume using the hydrogen peroxide of mass concentration 30% is 1mL, and sodium borohydride aqueous solution concentration is 100mmol/L；Institute State that to prepare response time of Nano silver piece be 5 minutes.

3. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described silicon chip Mother matrix is the N-type silicon chip of 1～10 Ω cm；The described employing oxygen plasma cleaning silicon chip mother matrix time is 1 minute；Institute State and clean the Fluohydric acid. mass concentration that used of pretreatment silicon chip mother matrix and be 5%, clean 1 minute.

4. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described preparation The silver nitrate aqueous solution concentration that silicon nanowire array is used is 5mmol/L, and hydrofluoric acid aqueous solution concentration is 4.8mol/L, Aqueous hydrogen peroxide solution concentration is 4.5mol/L.

5. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described preparation The hydrogen peroxide of silicon nanowire array-hf etching time is 3 minutes, controls to make a length of 2 μm of gained silicon nanowires, Distance between adjacent nanowires is 50-500nm；Every cm²Silicon nanowire array adds the amount of Nano silver piece 200nmol。

6. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described wet method Cleaning after etching is first used mass concentration 30% dust technology, is used 5% Fluohydric acid. again, is respectively washed 1 minute.

7. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described by silicon Nano-wire array argon plasma cleans, and the running voltage controlling plasma cleaning apparatus is 1kV, and instrument works Intracavity air pressure is 40Pa, and the time is 30 minutes.

8. the method improving silicon-based photovoltaic device photoelectric conversion efficiency as claimed in claim 1, is characterised by described addition The dripping quantity of poly-(3,4-Ethylenedioxy Thiophene)-poly-(styrene sulfonic acid) ethanol solution in silicon nanowire array is 20μL/cm²；Operation order is first to be added in silicon nanowire array by Nano silver piece, adds poly-(3,4-ethylenedioxies Thiophene)-the ethanol solution of poly-(styrene sulfonic acid), make Nano silver piece directly contact silicon nanowires, and be positioned at inorganic organic different Between the interface of matter knot.