阅读说明：本技术 一种具有阵列式微纳透镜结构的石墨烯/砷化镓太阳电池及其制备方法 (Graphene/gallium arsenide solar cell with array micro-nano lens structure and preparation method thereof ) 是由 李国强 邓曦 刘兴江 王文樑 于 2021-07-26 设计创作，主要内容包括：本发明公开了一种具有阵列式微纳透镜结构的石墨烯/砷化镓太阳电池及其制备方法。本发明的石墨烯/砷化镓太阳电池自下而上依次包括背面电极、砷化镓层、石墨烯层、栅电极和具有表面阵列式微纳透镜结构的薄膜。本发明制备的石墨烯/砷化镓太阳电池具有更高光利用效率,增强电池表面光吸收,提高光电转化效率等优点,制备的具有微透镜结构的薄膜能够更好的将电池表面入射光收集起来,便于太阳电池进行光伏效应,有利于制备高转化效率的石墨烯/砷化镓太阳电池。(The invention discloses a graphene/gallium arsenide solar cell with an array micro-nano lens structure and a preparation method thereof. The graphene/gallium arsenide solar cell sequentially comprises a back electrode, a gallium arsenide layer, a graphene layer, a gate electrode and a film with a surface array type micro-nano lens structure from bottom to top. The graphene/gallium arsenide solar cell prepared by the method has the advantages of higher light utilization efficiency, enhanced light absorption of the surface of the cell, improved photoelectric conversion efficiency and the like, and the prepared film with the micro-lens structure can better collect incident light on the surface of the cell, is convenient for the photovoltaic effect of the solar cell, and is beneficial to preparing the graphene/gallium arsenide solar cell with high conversion efficiency.)

1. A preparation method of a graphene/gallium arsenide solar cell with an array micro-nano lens structure is characterized by comprising the following steps:

(1) preparing a back electrode on one surface of the gallium arsenide substrate or the epitaxial wafer;

(2) transferring graphene to the other side of the gallium arsenide substrate or the epitaxial wafer in the step (1) by adopting wet transfer, and preparing a gate electrode on the surface of the graphene after drying;

(3) spin-coating nanoimprint lithography glue on the surface of the gate electrode and semi-solidifying the nanoimprint lithography glue into a film, and then preparing the semi-solidified film into a surface array type micro-nano lens pattern by adopting a nanoimprint lithography technology to obtain the graphene/gallium arsenide solar cell with an array type micro-nano lens structure;

the soft template used by the nanoimprint technology is a soft template with a nano lens structure, the surface pattern of the soft template is a concave mirror structure distributed in an array, the diameter of the pattern is 100-200 nm, the thickness of the pattern is 50-200 nm, and the distance between the patterns is 100-200 nm.

2. The preparation method of the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the spin coating process in step (3) is as follows: placing the back electrode-gallium arsenide-graphene-gate electrode obtained in the step (2) in a spin coater, dripping the nanoimprint lithography glue mixed solution at the central position of one surface of the gate electrode, wherein the rotation speed of the spin coater is 2000-5000 r/min, the spin coating time is 60-200 s, and the area ratio of the volume of the dripped nanoimprint lithography glue mixed solution to the gallium arsenide substrate or epitaxial wafer is 0.05-0.2 mL/cm²(ii) a The nanoimprint lithography glue mixed liquid is a mixed liquid of a GLR Primer tackifier and GLR-Plus ultraviolet nanoimprint lithography glue according to the volume ratio of 1: 1.

3. The preparation method of the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the temperature for semi-curing in the step (3) is 100-150 ℃ and the time is 1-4 min;

the conditions of the nano-imprinting technology in the step (3) are as follows: the working temperature is room temperature, the contact pressure is 5-20 MPa, the starting and resetting displacement speed is 0.5-2 mm/s, the contact and separation displacement speed is 0.01-0.05 mm/s, the ultraviolet exposure time is 30-120 s, and the curing time after exposure is 2-5 min.

4. The preparation method of the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the gate electrode in the step (2) comprises a main gate electrode and a fine gate electrode, the main gate electrode is distributed along the surface boundary of the graphene layer, the thickness is 50-150 nm, and the width is 50-200 μm; the thickness of the fine gate electrode is 50-150 nm, the width is 3-5 μm, and the distance is 200-500 μm.

5. The method for preparing the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the gate electrode in step (2) comprises fine gate electrodes with the thickness of 100nm, the width of 3 μm and the distance of 300 μm and main gate electrodes with the thickness of 100nm and the width of 100 μm distributed along the surface boundary of the graphene layer;

the spin coating time of the nano-imprint glue in the step (3) is 120 s;

the pattern parameters of the soft template in the step (3) are as follows: the diameter is 100-200 nm, the thickness is 50-200 nm, and the distance is 100-200 nm;

and (4) the ultraviolet exposure time in the nano-imprinting process in the step (3) is 60 s.

6. The method for preparing the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the surface array micro-nano lens patterns in step (3) are arranged in a cubic array.

7. The method for preparing the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the gallium arsenide epitaxial wafer in the step (1) refers to an epitaxial wafer epitaxially grown along a crystal plane (100);

the gallium arsenide substrate or epitaxial wafer in the step (1) is at least one of single junction gallium arsenide, double junction gallium indium phosphide/gallium arsenide and triple junction gallium indium phosphide/gallium arsenide/germanium;

the back electrode in the step (1) and the gate electrode in the step (2) are made of at least one of gold, silver, titanium, copper, platinum and nickel.

8. The preparation method of the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein in the step (2), the graphene has 1-5 layers; the wet transfer method comprises the following steps: soaking copper-based graphene into FeCl₃And taking out the copper base from the aqueous solution, transferring the graphene into acetone, ethanol, deionized water, dilute hydrochloric acid and deionized water in sequence by utilizing a polymethyl methacrylate sheet, respectively carrying out ultrasonic cleaning, and then transferring the graphene onto a gallium arsenide substrate.

9. The preparation method of the graphene/gallium arsenide solar cell with the array micro-nano lens structure according to claim 1, wherein the back electrode in step (1) is prepared by evaporation and annealing; and (3) preparing the gate electrode in the step (2) by adopting an evaporation method.

10. A graphene/gallium arsenide solar cell with an array micro-nano lens structure prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of solar cells, and particularly relates to a graphene/gallium arsenide solar cell with an array micro-nano lens structure and a preparation method thereof.

Background

In recent years, heterojunction solar cells based on the combination of two-dimensional materials (particularly graphene) and semiconductors have attracted considerable research interest. Although graphene has extremely high electron mobility, high light transmittance and high thermal conductivity, the graphene has excellent photoelectric characteristics, so that the graphene is very suitable for being applied to the photovoltaic field. But have a zero bandgap and do not, by themselves, efficiently convert light into electricity. Therefore, a graphene/gallium arsenide heterojunction solar cell based on gallium arsenide semiconductor material is a good choice for converting incident light into electricity. The current graphene/gallium arsenide heterojunction solar cell has low conversion efficiency. The highest efficiency measured by the graphene/gallium arsenide single-junction solar cell which is reported at present is 16.2%. Compared with the conventional polycrystalline silicon solar cell, the efficiency of the conventional polycrystalline silicon solar cell can reach 18.5% -22.8%, and the conventional gallium arsenide solar cell is complex in manufacturing process and high in cost, so that the photovoltaic performance of the graphene/gallium arsenide single-junction solar cell needs to be improved by using a new structural design.

Nanoimprint technology (NIL) is a method that uses mechanical contact extrusion to redistribute the imprinted material between the template and the substrate to form the desired pattern configuration. Compared with the traditional photoetching technology, the patterns manufactured by the nano-imprinting technology have higher resolution, have the characteristics of high yield, low cost, large-scale batch production and the like, can be used for preparing the designed patterns on the surface of the solar cell in batches by utilizing the nano-imprinting technology, and are favorable for preparing the film with the high-precision micro-nano structure.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention mainly aims to provide a preparation method of a graphene/gallium arsenide solar cell with an array micro-nano lens structure. The method can reduce the cost of the preparation process.

The invention also aims to provide the graphene/gallium arsenide solar cell with the array micro-nano lens structure prepared by the method.

The graphene/gallium arsenide solar cell prepared by the method has the characteristics of strong light absorption capacity, high photoelectric conversion efficiency and the like.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a graphene/gallium arsenide solar cell with an array micro-nano lens structure comprises the following steps:

(1) preparing a back electrode on one surface of the gallium arsenide substrate or the epitaxial wafer;

(2) transferring graphene to the other side of the gallium arsenide substrate or the epitaxial wafer in the step (1) by adopting wet transfer, and preparing a gate electrode on the surface of the graphene after drying;

(3) spin-coating nanoimprint lithography glue on the surface of the gate electrode and semi-solidifying the nanoimprint lithography glue into a film, and then preparing the semi-solidified film into a surface array type micro-nano lens pattern by adopting a nanoimprint lithography technology to obtain the graphene/gallium arsenide solar cell with an array type micro-nano lens structure;

the soft template used by the nanoimprint technology is a soft template with a nano lens structure, the surface pattern of the soft template is a concave mirror structure distributed in an array, the diameter of the pattern is 100-200 nm, the thickness of the pattern is 50-200 nm, and the distance between the patterns is 100-200 nm.

Preferably, the gallium arsenide epitaxial wafer in step (1) refers to an epitaxial wafer epitaxially grown along the (100) crystal plane, and the structure of the gallium arsenide substrate or the gallium arsenide epitaxial wafer is not particularly limited, and may be an epitaxial structure suitable for a gallium arsenide solar cell, which is well known to those skilled in the art.

Preferably, the gallium arsenide substrate or epitaxial wafer in step (1) needs to be sequentially cleaned by acetone/isopropanol, ethanol and deionized water before use.

Preferably, the gallium arsenide substrate or epitaxial wafer of step (1) is at least one of single junction gallium arsenide, double junction gallium indium phosphide/gallium arsenide and triple junction gallium indium phosphide/gallium arsenide/germanium.

Preferably, the back electrode in step (1) is prepared by conventional evaporation and annealing treatment.

Preferably, the material of the back electrode in step (1) and the material of the gate electrode in step (2) are both at least one of gold, silver, titanium, copper, platinum and nickel.

Preferably, the graphene in the step (2) has 1-5 layers; the wet transfer method comprises the following steps: soaking copper-based graphene into FeCl₃And taking out the copper base from the aqueous solution, sequentially transferring graphene into acetone, ethanol, deionized water, dilute hydrochloric acid and deionized water by utilizing a polymethyl methacrylate (PMMA) sheet, respectively carrying out ultrasonic cleaning for 5min, removing impurities, and then transferring the graphene onto a gallium arsenide substrate.

More preferably, the volume ratio of hydrochloric acid to water in the dilute hydrochloric acid is 1: 10.

Preferably, the drying in step (2) adopts vacuum-assisted drying to remove moisture.

Preferably, the gate electrode in the step (2) comprises a main gate electrode and a fine gate electrode, wherein the main gate electrode is distributed along the surface boundary of the graphene layer, the thickness of the main gate electrode is 50-150 nm, and the width of the main gate electrode is 50-200 μm; the thickness of the fine gate electrode is 50-150 nm, the width is 3-5 mu m, the distance is 200-500 mu m, and the width of 3 mu m and the distance of 300 mu m are more preferable.

Preferably, the gate electrode in the step (2) is prepared by an evaporation method.

Preferably, the spin coating process in the step (3) is as follows: placing the back electrode-gallium arsenide-graphene-gate electrode obtained in the step (2) in a spin coater, dripping the nanoimprint lithography glue mixed solution at the central position of one surface of the gate electrode, wherein the rotation speed of the spin coater is 2000-5000 r/min, the spin coating time is 60-200 s, and the area ratio of the volume of the dripped nanoimprint lithography glue mixed solution to the gallium arsenide substrate or epitaxial wafer is 0.05-0.2 mL/cm²。

More preferably, the spin-coating time is 120 s.

Preferably, the nanoimprint lithography glue in the step (3) is a mixed solution of a GLR Primer tackifier and a GLR-Plus ultraviolet nanoimprint lithography glue in a volume ratio of 1:1 (Qingdao Tianren micro-nano technology Co., Ltd.).

Preferably, the temperature for semi-curing in the step (3) is 100-150 ℃ and the time is 1-4 min.

Preferably, the nanoimprinting technique of step (3) is performed under the following conditions: the working temperature is room temperature, the contact pressure is 5-20 MPa, the starting and resetting displacement speed is 0.5-2 mm/s, the contact and separation displacement speed is 0.01-0.05 mm/s, the ultraviolet exposure time is 30-120 s, and the curing time after exposure is 2-5 min.

More preferably, the uv exposure time is 60 s.

Preferably, the nanoimprinting technique of step (3) includes the steps of:

placing the soft template in the template area, and aligning the scale marks; placing the sample on a substrate tray, calibrating the sample position; starting a nano-imprinting machine, and setting imprinting parameters; and starting a nano-imprinting program until nano-imprinting is finished, and taking out the obtained solar cell.

Preferably, after the surface array type micro-nano lens pattern is prepared in the step (3), the thin film at the position of the gate electrode contact is removed by etching, so that the solar cell contact is exposed and is convenient for connecting an external circuit.

Preferably, the surface array type micro-nano lens patterns in the step (3) are arranged in a cubic array.

Preferably, the pattern parameters of the soft template in the step (3) are: the diameter is 100-200 nm, the thickness is 50-200 nm, and the distance is 100-200 nm.

The graphene/gallium arsenide solar cell with the array micro-nano lens structure is prepared by the method.

Preferably, the graphene/gallium arsenide solar cell with the array micro-nano lens structure sequentially comprises a film layer, a gate electrode, a graphene layer, a gallium arsenide epitaxial wafer layer and a back electrode from top to bottom.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) compared with a common graphene/gallium arsenide heterojunction solar cell, the array micro-nano lens structure film structure is formed on the surface, so that the light absorption of the surface of the solar cell can be improved, incident light can be collected and incident on the surface of the solar cell better by the micro-nano lens structure, and the light utilization rate of the solar cell is improved.

(2) The film with the micro-nano lens structure on the surface of the solar cell adopts high-light-transmittance high-molecular polymers, so that the lighting of the solar cell is hardly influenced. The film pattern adopts a nano-imprinting technology, so that the preparation is convenient, the accuracy is good, the size of the micro-nano structure can be freely regulated and controlled, the one-step forming is easy, the preparation process of the solar cell is not changed, and the application range is wide.

(3) The micro-nano lens structure film on the surface of the solar cell can play a role in packaging and protecting the cell, and can prevent the surface of the solar cell from being oxidized under the action of moisture and oxygen in the air, so that the service life of the cell can be prolonged, and the stability of the cell can be improved.

Drawings

Fig. 1 is a schematic structural diagram of a graphene/gallium arsenide solar cell with a surface micro-nano lens structure film, wherein the array micro-nano lens structure film layer (1), a front (main) gate electrode (2), a graphene layer (3), a gallium arsenide epitaxial wafer layer (4) and a back electrode (5) are provided.

Fig. 2 is a schematic diagram of a soft template for preparing a micro-nano lens array pattern with corresponding parameters.

Fig. 3 shows the I-V characteristics of the graphene/gallium arsenide solar cell before and after the micro-nano lens array structure is introduced in example 1.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

Referring to fig. 1, the graphene/gallium arsenide solar cell of the invention sequentially comprises a thin film layer (1) of an array micro-nano lens structure, a front (main) gate electrode (2), a graphene layer (3), a gallium arsenide epitaxial wafer layer (4) and a back electrode (5) from top to bottom.

Referring to fig. 2, the mold used in the nanoimprint technology of the present invention is a soft template with a nano-lens structure, and the surface pattern of the template is a concave mirror structure distributed in an array.

The wet transfer method of the embodiment comprises the following steps: soaking copper-based graphene into FeCl₃Taking out the aqueous solutionAnd (3) copper-based graphene is sequentially transferred to acetone, ethanol, deionized water, dilute hydrochloric acid (the volume ratio of HCl to water is 1: 10) and deionized water by utilizing a polymethyl methacrylate (PMMA) sheet, ultrasonic cleaning is respectively carried out for 5min, impurities are removed, and then the graphene is transferred to a gallium arsenide substrate.

Example 1

(1) Ultrasonic cleaning is carried out on a gallium arsenide substrate epitaxial wafer (a (100) crystal face) (the substrate is 2 inches) by using acetone ethanol and deionized water in sequence, and then the substrate is taken out and dried by using a nitrogen gun; preparing a gold coating on one surface of the gallium arsenide substrate epitaxial wafer through vapor deposition and annealing treatment to serve as a back electrode;

(2) transferring graphene to one side of the gallium arsenide electrode which is not prepared by adopting wet transfer; drying under vacuum to remove water; gold is used as an electrode material to evaporate and coat fine gate electrodes with the thickness of 100nm, the width of 3 mu m and the interval of 300 mu m and main gate electrodes with the thickness of 100nm and the width of 100 mu m which are distributed along the surface boundary of the graphene layer on the surface of the graphene layer;

(3) dripping 0.1mL of nanoimprint lithography glue (mixed solution of GLR Primer tackifier and GLR-Plus ultraviolet nanoimprint lithography glue in a volume ratio of 1:1, Qingdao Tianren micro-nano technology Co., Ltd.) on the surface center of one side of the gate electrode in the step (2), spin-coating for 120s at 3000r/min, then placing in a 120 ℃ oven for heat preservation for 2min, and forming a semi-cured film structure on the surface of the cell;

(4) preparing a surface array type micro-nano lens pattern by using a nano imprinting technology, placing a soft template in a template area, and aligning to the scale mark; placing the sample on a substrate tray, calibrating the sample position; starting a nano-imprinting machine, and setting imprinting parameters; starting a nano-imprinting program until nano-imprinting is finished;

the template pattern of the soft membrane plate is an array type micro-nano concave mirror structure distributed in a cubic array, and is shown in figure 2, the diameter is 100nm, the thickness is 50nm, and the pattern array interval is 100 nm; the setting conditions of the nano-imprinting technology stamping machine are as follows: the working temperature is room temperature, the contact pressure is 10MPa, the starting and resetting displacement speed is 1mm/s, the contact and separation displacement speed is 0.02mm/s, the ultraviolet irradiation is carried out for 60s, and then the imprinting state is kept for 180s, so that the completely cured film with the reverse pattern of the mold is obtained;

(5) etching is carried out to remove the stamping glue covered at the contact point of the gate electrode.

Example 1I-V characteristic curve of finally prepared graphene/GaAs solar cell referring to FIG. 3, open circuit voltage V_oc0.765V, short-circuit current density I_SCIs 24.1mAcm^-2The fill factor FF was 50.14% and the photoelectric conversion efficiency was 9.39%.

For the graphene/gallium arsenide solar cell (namely the solar cell obtained in the steps 1 and 2) of which the surface micro-nano lens structure array film is not prepared by adopting the nano imprinting technology, the open-circuit voltage V is_oc0.758V, short-circuit current density I_SCIs 20.8mA cm^-2The fill factor FF was 55.14% and the photoelectric conversion efficiency was 8.51%.

Example 2

Unlike example 1, the fine gate pitch of the surface gate electrode prepared in example 2 was 500 μm, and the surface film thickness was changed by controlling the imprint paste spin-coating time to 60 s. The parameters of the selected flexible membrane pattern are diameter 200nm, thickness 50nm, pattern array interval 200nm, ultraviolet exposure time 30s, and other conditions and preparation methods are the same as those of the embodiment 1. Finally prepared graphene/gallium arsenide solar cell open-circuit voltage V_oc0.758V, short-circuit current density I_SCIs 21.3mA cm^-2The fill factor FF was 50.24% and the photoelectric conversion efficiency was 8.11%.

Example 3

Different from the embodiment 1, the embodiment 3 controls the spin coating time of the nano-imprint glue to be 90s, and selects the parameters of the soft film plate pattern as the diameter of the lens pattern 150nm, the thickness of the lens pattern 50nm, the pattern array interval 150nm and the ultraviolet exposure time of 90s, and the other conditions and the preparation method are the same as those of the embodiment 1. Finally prepared graphene/gallium arsenide solar cell open-circuit voltage V_oc0.758V, short-circuit current density I_SCIs 22.5mA cm^-2The fill factor FF was 50.11% and the photoelectric conversion efficiency was 8.55%.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.