CN111192969B

CN111192969B - Structure and preparation method of light-emitting field effect transistor based on poly-F8BT crystal

Info

Publication number: CN111192969B
Application number: CN202010019461.9A
Authority: CN
Inventors: 陈润泽; 李钰; 卜镜元
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2020-01-08
Filing date: 2020-01-08
Publication date: 2021-01-05
Anticipated expiration: 2040-01-08
Also published as: CN111192969A

Abstract

The invention belongs to the field of preparation of novel electronic components, and relates to a structure and a preparation method of a light-emitting field effect tube based on poly-F8BT crystal. The invention combines the controlled evaporation self-assembly method with the two-solvent scheme to obtain a crystal array with high crystal quality, the coverage of the film is also greatly improved, and the crystal width of the organic film is widened. As a light-emitting layer, the highly ordered crystal array obtained by the method of the present invention has lower turn-on voltage, higher external quantum efficiency and better light-emitting performance than an organic light-emitting field effect transistor based on a common thin film as a light-emitting layer. Compared with the thin film prepared by spin coating, the light-emitting layer prepared by the double solvent evaporation method in the present invention can realize the fast directional transport of carriers.

Description

Light-emitting field effect transistor structure based on poly F8BT crystal and preparation method

Technical Field

The invention belongs to the field of preparation of novel electronic components, and relates to a light-emitting field effect transistor structure based on poly F8BT crystal and a preparation method thereof.

Background

Light emitting field effect transistors (LFETs) are light emitting diodes incorporating switching features that allow direct access to organic semiconductors through spatially resolved probes to form charge recombination zones, allowing organic devices to be used more widely in optoelectronic integrated circuits. But such devices have the disadvantage of being not externally quantum efficient. To achieve higher efficiency, the excitons in the recombination layer are separated from the charges in the adjacent charge transport and injection layers using an organic semiconductor. Organic light emitting field effect transistors (OLETs) can combine the electrical switching properties of organic transistors with the light emitting properties of organic light emitting diodes. New device structures are provided for a range of applications for display, illumination and integrated optoelectronic devices. An advantage of this device structure is that the location of the recombination region can be moved within the transistor channel away from any absorbing metal electrodes by the applied gate and drain voltages. This minimizes photon loss at the electrodes and makes OLET a widely studied device structure, especially for applications requiring high excitation densities, such as organic electric injection lasers.

However, most of the methods for preparing an OLET light-emitting layer are prepared by spin coating or evaporation, and the light-emitting layer prepared by the methods is usually not directionally crystallized, so that the light-emitting efficiency of the device is very low, and the potential of the OLET device cannot be fully exerted, which requires a method for preparing a highly ordered crystal array of the light-emitting layer.

The small molecular organic semiconductor which can be processed by solution has relatively high charge carrier transmission and low manufacturing cost, so that the small molecular organic semiconductor is deeply researched, and has wide application prospect in the field of large-area flexible electronics. However, since small molecule organic semiconductor thin films typically exhibit random crystal orientation and poor coverage, which results in significant changes in the performance of Organic Thin Film Transistors (OTFTs), good alignment of the crystals is necessary to achieve uniformity of the performance of the OLETs. The films obtained in these above works still show low area coverage, which must be improved to produce high mobility OLETs with performance uniformity.

Disclosure of Invention

In order to solve the problems, the invention provides a light-emitting field effect transistor based on poly (F8BT) crystal and a preparation method thereof, and the light-emitting field effect transistor is based on poly (9, 9-dioctyl fluorenyl-2, 7-diyl) (F8BT) crystal, combines a controlled evaporation self-assembly method with a two-solvent scheme, and utilizes the growth of a small-molecule organic semiconductor on a slightly inclined substrate to arrange a good and highly ordered banded small-molecule organic semiconductor F8BT crystal array in the inclined direction of the substrate so as to control the crystal growth and enhance the area coverage rate of the organic semiconductor. The organic luminous field effect tube prepared by the method has low open voltage and high external quantum efficiency, can realize bipolar transmission, and can greatly improve the luminous performance of an OLET device.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a light-emitting field effect transistor structure based on poly F8BT crystal comprises multiple layers, wherein a top gate structure is adopted, the top gate structure is from bottom to top, and the first layer is a transparent glass substrate; the two sides of the second layer are respectively a source electrode and a drain electrode, and the middle part is a luminous layer; an electron injection layer and a hole injection layer are respectively arranged at two sides of the third layer, and a light-emitting layer is arranged in the middle of the third layer; the fourth layer is a luminous layer and is in an integral structure with the luminous layers of the second layer and the third layer; the fifth layer is an insulating layer; the sixth layer is a grid;

the source electrode is made of aluminum (Al); the grid electrode and the drain electrode are made of gold (Au); the material of the light-emitting layer is F8BT crystal array; the electron injection layer is made of zinc oxide (ZnO); the hole injection layer is made of molybdenum trioxide (MoO)₃) (ii) a The insulating layer is made of polymethyl methacrylate (PMMA).

The thickness of the luminescent layer is 70-90nm (including the cross part with the second layer and the third layer).

The thickness of the insulating layer is 600-700 nm.

The thickness of the hole injection layer is 3-5 nm.

The thickness of the electron injection layer is 3-5 nm.

The thickness of the source electrode and the drain electrode is 30-50 nm.

The thickness of the grid electrode is 10-16 nm.

The source electrode and the drain electrode are interdigital; the grid is sheet.

A preparation method of a light-emitting field effect transistor structure based on poly F8BT crystal comprises the following steps:

step 1, placing the transparent glass substrate in liquid detergent, deionized water, methanol and isopropanol in sequence, ultrasonically cleaning, and then drying.

Step 2, placing a mask on the transparent glass substrate obtained in the step 1, wherein patterns on the used mask are in a comb shape, the width of the hollow stripes is the same as that of the source electrode and the drain electrode, one ends of the hollow stripes are not communicated, the other ends of the hollow stripes are communicated, the communicated ends extend outwards, the length of the communicated ends is longer than the distance between the two outermost comb teeth, and the communicated ends are used for connecting each electrode; adjusting the position of the mask plate to enable the hollow stripes to be positioned at one end of the transparent glass substrate; placing the mask plate and the transparent glass substrate which are fixed together in an evaporation coating machine, and depositing 30-50 nm-thick aluminum on the transparent glass substrate at the speed of 0.3-0.5nm/s to be used as a source electrode; then, the evaporation source is switched to deposit zinc oxide with the thickness of 3-5nm on the source electrode at the speed of 0.1-0.3nm/s as an electron injection layer.

Step 3, taking the edge of the outward extending part of the communicating end of the mask as a symmetry axis, symmetrically turning the mask for 180 degrees, then placing the mask on the transparent glass substrate, enabling the hollow stripes to be positioned at the other end of the transparent glass substrate, fixing the hollow stripes and the transparent glass substrate, placing the mask and the transparent glass substrate in an evaporation coating machine, and depositing gold with the thickness of 30-50nm on the transparent glass substrate at the speed of 0.3-0.5nm/s to be used as a drain electrode; then, molybdenum trioxide with a thickness of 3-5nm is deposited on the drain electrode as a hole injection layer by switching the evaporation source at a rate of 0.1-0.3 nm/s.

And 4, taking the mask plate out of the transparent glass substrate obtained in the step 3, then placing the glass substrate in an HMDS solution at the temperature of 130-140 ℃ for carrying out hydrophobization treatment for 20-30 minutes, and then horizontally placing a cylindrical glass bottle on the treated transparent glass substrate, so that the side wall surface of the cylindrical glass bottle is in contact with the transparent glass substrate, and the cylinder is positioned outside the two electrodes, so that crystals can grow between the two electrodes.

Step 5, dissolving F8BT in a mixed solution of xylene and n-butyl acetate to obtain an F8BT solution, wherein the concentration of F8BT is 10-15mg/ml, and the ratio of the xylene to the n-butyl acetate is 5:1-20: 1; dripping the F8BT solution into the gap between the glass bottle and the transparent glass substrate, heating and evaporating at 60-80 deg.C, and removing the cylindrical glass bottle to obtain F8BT crystal; wherein a light-emitting layer having a thickness of 70-90nm is obtained.

And 6, dissolving PMMA in n-butyl acetate to obtain a PMMA solution with the concentration of 60-70mg/ml, and spin-coating a layer of 700n MMA transparent film with the thickness of 600-700n MMA as an insulating layer on the F8BT crystal obtained in the step 5 by using a spin coater at the speed of 4000-5000 rpm.

And 7, putting the transparent glass substrate which is coated with the insulating layer in an evaporation coating machine, and evaporating gold with the thickness of 3-5nm as a grid on the PMMA transparent film at the speed of 0.1-0.3 nm/s.

The mask version, the width of the un-fretwork department between two fretwork stripes is 60um, fretwork stripe length is 3 mm.

The invention has the beneficial effects that:

1. the invention combines the controlled evaporation self-assembly method and the double-solvent scheme to obtain the crystal array with high crystal quality, greatly improves the film coverage and widens the crystal width of the organic film.

2. Compared with an organic light-emitting field effect transistor which takes a common film as a light-emitting layer, the highly ordered crystal array obtained by the method has lower starting voltage, higher external quantum efficiency and better light-emitting performance.

3. Compared with a film prepared by spin coating, the luminescent layer prepared by the double-solvent evaporation method can realize rapid directional transmission of current carriers.

Drawings

Fig. 1 is a schematic cross-sectional view of a light-emitting field effect transistor structure based on poly F8BT transistors according to the present invention.

Fig. 2 is a microscope image of a highly ordered F8BT crystal array.

Fig. 3 is a microscope view of the completed device from above.

FIG. 4 is an I-V plot of source-drain current versus source-drain voltage at a gate voltage of 0 VoA.

FIG. 5 is an I-V plot of source drain current versus gate voltage for a source drain voltage of-100 Von.

FIG. 6 is a reticle schematic.

Fig. 7 is a schematic of crystal formation.

Detailed Description

The following further describes the specific embodiments of the present invention with reference to the drawings and technical solutions.

As shown in fig. 1, a light-emitting field effect transistor structure based on poly F8BT crystal comprises a multilayer structure, from bottom to top, a first layer being a transparent glass substrate; the two sides of the second layer are respectively provided with a source electrode and a drain electrode, the middle part is provided with a luminous layer, the source electrode is made of aluminum, and the drain electrode is made of gold; an electron injection layer and a hole injection layer are respectively arranged at two sides of the third layer, and a light-emitting layer is arranged in the middle of the third layer; the fourth layer is a light-emitting layer, is of an integral structure with the light-emitting layers of the second layer and the third layer, and is made of F8BT crystal array; the fifth layer is an insulating layer made of polymethyl methacrylate; the sixth layer is a grid made of gold.

The preparation method of the light-emitting field effect transistor structure based on the poly F8BT crystal comprises the following steps:

example 1

Step 1, cleaning a transparent conductive glass substrate, wherein the adopted substrate is common transparent glass

Adopting a transparent substrate, and chemically cleaning the substrate, wherein the cleaning steps are as follows: firstly, ultrasonically oscillating a substrate for 20min by using liquid detergent and deionized water, then sequentially cleaning the substrate for 20min by using the deionized water, acetone and isopropanol by using the same method, and finally drying the substrate by using nitrogen.

And putting the cleaned glass into Plasma, and carrying out ultraviolet oxygen treatment for 10 min.

Step 2, fixing the cleaned and dried substrate and the mask, placing the sample in an evaporation coating machine, and vacuumizing to 6.0 multiplied by 10^-4Pa, depositing 30nm aluminum electrode on the substrate at the speed of 0.3 nm/s; then closing the evaporation source to switch the evaporation channel, and waiting for vacuum pumping again until the vacuum is reduced to 6.0 × 10^-4Pa, 3nm zinc oxide was deposited on the aluminum electrode at a rate of 0.1 nm/s. The structure of the reticle used is shown in fig. 6.

Step 3, taking the substrate out of the mask plate, transferring the substrate to 180 degrees, putting the substrate into an evaporation coating machine again, and vacuumizing the substrate to 6.0 multiplied by 10^-4Pa, depositing a 30nm gold electrode on the substrate at a speed of 0.3 nm/s; then closing the evaporation source to switch the evaporation channel, and waiting for the vacuum degree to be as low as 6.0 multiplied by 10^-4Pa, 3nm molybdenum trioxide was deposited on the gold electrode at a rate of 0.1 nm/s.

And 4, adhering the substrate with the evaporated electrodes on a culture dish, reversely buckling the culture dish on the HMDS solution heated at the temperature of 130 ℃, performing hydrophobization treatment for 20 minutes by using solution steam, and placing a cylindrical glass bottle on the treated substrate.

And 5, weighing 10mgF8BT by using a balance scale, weighing 1ml of mixed solution of xylene and n-butyl acetate (the ratio of the xylene to the n-butyl acetate is 5:1) by using a liquid transfer gun, dissolving F8BT in the mixed solution, heating and stirring for one hour at 60 ℃, dripping the F8BT solution into a gap between a glass bottle and a substrate, heating for drying by distillation, and growing into F8BT crystals to obtain a 70nm light-emitting layer. The principle of crystal formation is shown in fig. 7, and the resulting highly ordered F8BT crystal array is shown in fig. 2.

And 6, weighing 60mg of PMMA by using a balance scale, measuring 1ml of n-butyl acetate solution by using a pipette, dissolving the PMMA in the n-butyl acetate, heating and stirring for one hour at the temperature of 60 ℃, and spin-coating a 600 nm-thick PMMA transparent film on the F8BT crystal by using a spin coater at the speed of 4000 rpm.

Step 7, putting the spin-coated substrate in an evaporation coating machine, and vacuumizing to 6.0 multiplied by 10^-4Pa, a 10nm transparent gold electrode was deposited on PMMA at 0.1nm/s as a gate electrode.

Finally, the light-emitting field effect transistor structure based on the poly F8BT crystal is obtained, as shown in FIG. 3. When the grid voltage is 0 volt ampere, the I-V curve of the source-drain current and the source-drain voltage is shown in figure 4, which shows that the device has good conductivity, when the source-drain voltage is-100 volt ampere, the I-V curve of the source-drain current and the grid voltage is shown in figure 5, and the grid voltage has good regulation and control performance on the hole-electron recombination region.

Example 2

Adopting a transparent substrate, and chemically cleaning the substrate, wherein the cleaning steps are as follows: firstly, ultrasonically oscillating a substrate by detergent and deionized water for 30min, then sequentially cleaning the substrate by the deionized water, acetone and isopropanol for 50min by the same method, and finally blowing the substrate by nitrogen.

And putting the cleaned glass into Plasma, and carrying out ultraviolet oxygen treatment for 20 min.

Step 2, fixing the cleaned and dried substrate and the mask plate,and the sample is placed in an evaporation coating machine, and vacuum pumping is carried out until the vacuum is as low as 5.0 x 10^-4Pa, depositing 40nm of aluminum electrode on the substrate at the speed of 0.4 nm/s; then closing the evaporation source to switch the evaporation channel, and waiting for vacuum pumping again until the vacuum is as low as 5.0 x 10^-4Pa, 4nm of zinc oxide was deposited on the aluminum electrode at a rate of 0.2 nm/s.

Step 3, taking the substrate out of the mask plate, transferring the substrate to 180 degrees, putting the substrate into an evaporation coating machine again, and vacuumizing the substrate to 4.0 multiplied by 10^-4Pa, depositing a 40nm gold electrode on the substrate at a speed of 0.4 nm/s; then closing the evaporation source to switch the evaporation channel, and waiting for the vacuum degree to be as low as 5.0 multiplied by 10^-4Pa, 4nm of molybdenum trioxide was deposited on the gold electrode at a rate of 0.2 nm/s.

And 4, adhering the substrate with the evaporated electrodes on a culture dish, reversely buckling the culture dish on the HMDS solution heated at the temperature of 140 ℃, performing hydrophobization treatment for 30 minutes by using solution steam, and placing a cylindrical glass bottle on the treated substrate.

And 5, weighing 12mgF8BT by using a balance scale, weighing 1ml of mixed solution of xylene and n-butyl acetate in a certain proportion (the ratio of the xylene to the n-butyl acetate is 10:1) by using a liquid transfer gun, dissolving F8BT in the mixed solution, heating and stirring for one hour at 70 ℃, dripping the F8BT solution into a gap between a glass bottle and a substrate, heating and waiting for evaporation to dryness to grow F8BT crystals, and obtaining the 80nm light-emitting layer.

And 6, taking 65mg of PMMA by using a balance scale, measuring 1ml of n-butyl acetate solution by using a pipette, dissolving the PMMA in the n-butyl acetate, heating and stirring for half an hour at 70 ℃, and spin-coating a layer of PMMA transparent film with the thickness of 650nm on the F8BT crystal by using a spin coater at the speed of 4500 rpm.

And 7, placing the spin-coated substrate in an evaporation coating machine, vacuumizing to 6.0 multiplied by 10 < -4 > Pa, and evaporating a 13nm transparent gold electrode on PMMA by 0.2nm/s to be used as a grid electrode.

Example 3

Adopting a transparent substrate, and chemically cleaning the substrate, wherein the cleaning steps are as follows: firstly, ultrasonically oscillating a substrate by detergent and deionized water for 10min, then sequentially cleaning the substrate by the deionized water, acetone and isopropanol for 60min by the same method, and finally blowing the substrate by nitrogen.

And putting the cleaned glass into Plasma, and carrying out ultraviolet oxygen treatment for 40 min.

Step 2, fixing the cleaned and dried substrate and the mask, placing the sample in an evaporation coating machine, and vacuumizing to 7.0 multiplied by 10^-4Pa, depositing 50nm of aluminum electrode on the substrate at the speed of 0.5 nm/s; then closing the evaporation source to switch the evaporation channel, and waiting for vacuum pumping again until the vacuum is reduced to 7.0 × 10^-4Pa, 5nm of zinc oxide was deposited on the aluminum electrode at a rate of 0.3 nm/s.

Step 3, taking the substrate out of the mask plate, transferring the substrate to 180 degrees, putting the substrate into an evaporation coating machine again, and vacuumizing the substrate to 7.0 multiplied by 10^-4Pa, depositing a 50nm gold electrode on the substrate at a speed of 0.5 nm/s; then closing the evaporation source to switch the evaporation channel, and waiting for the vacuum degree to be as low as 7.0 multiplied by 10^-4Pa, 5nm of molybdenum trioxide was deposited on the gold electrode at a rate of 0.3 nm/s.

And 4, adhering the substrate with the evaporated electrodes on a culture dish, reversely buckling the culture dish on the HMDS solution heated at 135 ℃, performing hydrophobization treatment for 10 minutes by using solution steam, and placing a cylindrical glass bottle on the treated substrate.

And 5, weighing 15mg of F8BT by using a balance scale, measuring 1ml of mixed solution of xylene and n-butyl acetate (the ratio of the xylene to the n-butyl acetate is 20:1) in a certain ratio by using a liquid transfer gun, dissolving F8BT in the mixed solution, heating and stirring at 80 ℃ for one hour, dripping the F8BT solution into a gap between a glass bottle and a substrate, heating and waiting for evaporation to dryness to grow into F8BT crystals, and obtaining a 90nm light-emitting layer.

And 6, weighing 70mg of PMMA by using a balance scale, measuring 1ml of n-butyl acetate solution by using a liquid transfer gun, dissolving the PMMA in the n-butyl acetate, heating and stirring for one hour at 80 ℃, and spin-coating a layer of PMMA transparent film with the thickness of 700nm on the F8BT crystal by using a spin coater at the speed of 5000 rpm.

And 7, placing the spin-coated substrate in an evaporation coating machine, vacuumizing to 6.0 multiplied by 10 < -4 > Pa, and evaporating a 16nm transparent gold electrode on PMMA by 0.3nm/s to be used as a grid electrode.

Claims

1. a preparation method based on the light-emitting field effect tube structure of poly-F8BT crystal, is characterized in that, described light-emitting field effect tube structure comprises multi-layer, adopts top grid structure, from bottom to top, the first layer is a transparent glass substrate The two sides of the second layer are the source electrode and the drain electrode respectively, and the middle is the light-emitting layer; the two sides of the third layer are the electron injection layer and the hole injection layer, respectively, and the middle is the light-emitting layer; the fourth layer is the light-emitting layer, which is the same as The light-emitting layers of the second layer and the third layer are integrated; the fifth layer is an insulating layer; the sixth layer is a gate electrode;

The material of the source electrode is aluminum; the material of the gate electrode and the drain electrode is gold; the material of the light-emitting layer is F8BT crystal array; the material of the electron injection layer is zinc oxide; The material of the layer is molybdenum trioxide; the material of the insulating layer is polymethyl methacrylate;

Described preparation method, steps are as follows:

Step 1. Place the transparent glass substrate in detergent, deionized water, methanol, and isopropanol for ultrasonic cleaning in sequence, and then dry;

Step 2. Place the mask on the transparent glass substrate obtained in Step 1. The pattern on the mask used is comb-like, and the width of the hollow stripes is the same as the width of the source and drain electrodes. One end is not connected, the other end is connected, and the connected end is extended outward, so that the length of the connected end is longer than the distance between the two comb teeth at the outermost end, and the connected end is used to connect each electrode; adjust the position of the mask so that the The hollow stripes are located at one end of the transparent glass substrate; the fixed mask and the transparent glass substrate are placed in an evaporative coating machine to deposit aluminum with a thickness of 30-50nm on the transparent glass substrate at a speed of 0.3-0.5nm/s. As the source electrode; then switch the evaporation source to deposit zinc oxide with a thickness of 3-5nm on the source electrode at a speed of 0.1-0.3nm/s as an electron injection layer;

Step 3. Taking the edge of the connecting end of the reticle as the axis of symmetry, turn the reticle symmetrically by 180° and place it on the transparent glass substrate, so that the hollow stripes are located at the other end of the transparent glass substrate. After fixing, place it in an evaporation coating machine, and deposit gold with a thickness of 30-50nm on a transparent glass substrate at a speed of 0.3-0.5nm/s as a drain; then switch the evaporation source to drain the drain at a speed of 0.1-0.3nm/s. Molybdenum trioxide with a thickness of 3-5nm is deposited on the pole as a hole injection layer;

Step 4. Take the mask out from the transparent glass substrate obtained in step 3, then place the glass substrate in the HMDS solution at 130-140° C. for hydrophobization treatment for 20-30 minutes, and then place the transparent glass substrate on the treated transparent glass substrate for 20-30 minutes. A cylindrical glass bottle is placed horizontally on the top, so that the side wall surface of the cylindrical glass bottle is in contact with the transparent glass substrate, and the cylindrical glass bottle is located outside the two electrodes, so that crystals are grown between the two electrodes;

Step 5. F8BT is dissolved in the mixed solution of xylene and n-butyl acetate to obtain F8BT solution, wherein the concentration of F8BT is 10-15mg/ml, and the ratio of xylene and n-butyl acetate is 5:1-20:1; The F8BT solution was dropped into the gap between the glass bottle and the transparent glass substrate, heated and evaporated to dryness at a temperature of 60-80 °C, and the cylindrical glass bottle was removed to obtain F8BT crystals; wherein a light-emitting layer with a thickness of 70-90 nm was obtained. ;

Step 6. Dissolve PMMA in n-butyl acetate to obtain a PMMA solution with a concentration of 60-70mg/ml. On the F8BT crystal obtained in step 5, spin-coat a layer with a thickness of 600 at a speed of 4000rpm-5000rpm with a glue spinner. -700nm PMMA transparent film as insulating layer;

Step 7. Place the transparent glass substrate on which the insulating layer has been spin-coated in an evaporation coating machine, and evaporate gold with a thickness of 3-5 nm on the PMMA transparent film at a speed of 0.1-0.3 nm/s as a gate.

2. a kind of preparation method based on the light-emitting field effect tube structure of poly-F8BT crystal according to claim 1, is characterized in that:

The thickness of the light-emitting layer is 70-90nm;

The thickness of the insulating layer is 600-700nm;

The thickness of the hole injection layer is 3-5nm;

The thickness of the electron injection layer is 3-5nm;

The thickness of the source electrode and the drain electrode is 30-50nm;

The gate thickness is 10-16nm;

The source electrode and the drain electrode are interdigitated; the gate electrode is sheet-shaped.

3. The method for preparing a light-emitting field effect transistor structure based on poly-F8BT crystal according to claim 1, wherein the mask plate has a width of 60um between the two hollow stripes without hollowing out, The hollow stripe length is 3mm.