Preparation method of single crystal photovoltaic cell

Abstract

The invention belongs to the technical field of preparation of single-crystal photovoltaic cells, and particularly relates to a preparation method of a single-crystal photovoltaic cell, which comprises the following steps: S1, starting to grow a rubrene single crystal, placing the rubrene single crystal on a red-core single-crystal substrate after the growth is completed, and performing low-evaporation-rate deposition on the grown rubrene single crystal by using a vacuum evaporator to obtain a deposition solution; then, the rubrene single crystal grows a red-core homoepitaxial film on a red-core single crystal substrate, and doping is carried out through a co-evaporation method; by using the doping technology of homoepitaxial growth of the rubrene single crystal layer, transverse hole transmission and collection of holes from the whole region of the pn homojunction occur, the carrier collection efficiency is improved, meanwhile, the holes generated in the pn homojunction can be collected by a hole collection electrode through a p-type hole collection path, and through the application of the method, the performance of the solar cell is improved. Electrons generated in the pn homojunction can be directly collected by the electrode.

Description

Technical Field

[0001] The invention belongs to the technical field of single crystal photovoltaic cell preparation, and in particular relates to a method for preparing a single crystal photovoltaic cell. Background Art

[0002] Monocrystalline photovoltaic cells are solar cells made of single-crystal silicon materials. Their core principle is to convert sunlight into electrical energy through the photoelectric effect. They are widely used in modern solar energy technology.

[0003] Patent publication number CN109192798B discloses a method for manufacturing a P-type monocrystalline silicon HIT photovoltaic cell, wherein it is mainly proposed that in the development history of silicon heterojunction solar cells, the doping type of the silicon substrate, the surface morphology of the silicon substrate, the preparation process of the gate, the annealing process of the transparent conductive layer, and the specific structure of the cell are usually improved to improve the photoelectric conversion efficiency of the silicon heterojunction solar cell. However, this method still has some disadvantages in the process room used. Therefore, by selecting a P-type monocrystalline silicon wafer as the silicon substrate, optimizing the number of N-type amorphous silicon layers and P-type amorphous silicon layers on the upper and lower surfaces of the P-type monocrystalline silicon wafer, the thickness of each layer, and the relationship between the size and specific value of the doping concentration of each layer, it is beneficial to the separation and transmission of electrons and holes in the P-type monocrystalline silicon HIT photovoltaic cell, thereby effectively improving the short-circuit current and fill factor of the P-type monocrystalline silicon HIT photovoltaic cell, thereby improving the photoelectric conversion efficiency of the P-type monocrystalline silicon HIT photovoltaic cell;

[0004] Through the above-mentioned known patent contents, we found that there are still some areas that can be improved in the actual use process, so we set our sights on organic single crystals. Organic single crystals have high carrier mobility. At the same time, since the high carrier mobility is manifested along the π-π stacking of organic molecules parallel to the crystal surface, and the diffusion length of excitons in organic single crystals is relatively long, we began to study the body doping technology for homoepitaxial growth of rubrene single crystal layers. When the existing organic single crystals are used in the field of batteries, the electrons and holes inside them move slowly in the material, so the carrier collection ability is often not strong. In this study, we tried to prepare doped rubrene single crystal photovoltaic cells. The entire photocurrent generated in the homojunction is collected by the p-doped homoepitaxial layer, so the device can improve its collection efficiency while also improving better conductivity.

[0005] Based on this, we designed a method for preparing single-crystal photovoltaic cells. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a single-crystal photovoltaic cell, which can improve the carrier collection efficiency through lateral hole transport and hole collection from the entire area of ​​the pn homojunction.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for preparing a single-crystal photovoltaic cell, including:

[0009] S1, starting to grow a rubrene single crystal, placing the rubrene single crystal on a red core single crystal substrate after the growth is completed, using a vacuum evaporator to perform low evaporation rate deposition on the grown rubrene single crystal, and then the rubrene single crystal will grow a homoepitaxial film of the red core on the red core single crystal substrate, and then doping is performed by a co-evaporation method;

[0010] S2, Fe2Cl6 and Cs2CO3 were used as acceptor and donor dopants respectively for doping in a preset method, and then the p-type Fe2Cl6 and Cs2CO3 with a doping concentration of 10000ppm were added. + and n ± Rubrene film is inserted into the Ag electrode and p - and n - type crystals to form an ohmic contact. At this time, by using p + The Ag electrode forms an ohmic contact with the p-type rubrene single crystal to complete the preparation.

[0011] In some embodiments, the rubrene single crystal in S1 is grown by physical vapor transport in nitrogen at 0.1 atmospheres, and the growth thickness of the rubrene single crystal is in the range of 2-5 μm.

[0012] In some embodiments, the low evaporation rate in S1 is specifically 3-3.3×10-3nm / s at room temperature. -1 Evaporation at a rate of .

[0013] In some embodiments, the preset method in S2 is to add Fe2Cl6 and Cs2CO3 at a doping concentration of 1:10ppm corresponding to 3-3.3×10-8 and 3-3.3×10-7nm / s-1 The doping is performed at a dopant evaporation rate of , and the preset method is achieved by using a slit rotating disk with an aperture ratio of 1:100 to reduce the evaporation rate.

[0014] In some embodiments, the specific thickness of the rubrene film in S2 is 10-15 nm, and the lateral gap between the two electrodes in S2 is maintained at 0.05-1 mm.

[0015] In some embodiments, the p-type homoepitaxial layer in S2 can serve as a lateral hole transport layer.

[0016] In some embodiments, the width of the pn homojunction in S2 is the width of the Ag electrode, which is maintained at 2-3 mm. The area of ​​the pn homojunction is 2-3 mm×L mm, where L represents the length of the pn homojunction and the value of L fluctuates between 0.1-1.0 mm.

[0017] In some embodiments, the ohmic electrode in S2 contacting the p-layer is a pure hole device.

[0018] The technical effects achieved by the present invention are:

[0019] 1. By using the doping technology of homoepitaxially grown rubrene single crystal layer, lateral hole transport and hole collection from the entire area of ​​the pn homojunction occur, improving the carrier collection efficiency;

[0020] 2. At the same time, the holes generated in the pn homojunction can also be collected by the hole collection electrode through the p-type hole collection path;

[0021] 3. Through the application of this method, the electrons generated in the pn homojunction can be directly collected by the electrode. DETAILED DESCRIPTION

[0022] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0023] Example:

[0024] A method for preparing a single-crystal photovoltaic cell, comprising:

[0025] First, the growth of rubrene single crystal is started, and after the growth is completed, the rubrene single crystal is placed on a red core single crystal substrate, and a vacuum evaporator is used to perform low evaporation rate deposition on the grown rubrene single crystal, and then the rubrene single crystal will grow a homoepitaxial film of the red core on the red core single crystal substrate, and then doping is performed by a co-evaporation method;

[0026] Finally, Fe2Cl6 and Cs2CO3 were used as acceptor and donor dopants, respectively, and then the p-type Fe2Cl6 and Cs2CO3 with a doping concentration of 10000ppm were doped. + and n ± Rubrene film is inserted into the Ag electrode and p - and n - type crystals to form an ohmic contact. At this time, by using p + The Ag electrode forms an ohmic contact with the p-type rubrene single crystal to complete the preparation.

[0027] Through the above steps, the preparation of the doped rubrene film is finally completed. The film has preset electrical and photoelectric properties, so it can be used in various photoelectric applications. It should be added that the doped organic single crystal cell is a functionally separated photovoltaic cell, in which the p-type homoepitaxial layer acts as a hole transport layer, the pn homojunction acts as an exciton dissociator, and the single crystal substrate acts as an exciton collector. With this as the background, the process preparation in the above scheme can be completed. Compared with the existing organic photovoltaic cells, it should be noted that the efficiency of the existing organic photovoltaic cells is relatively low, usually between 5% and 15%, and the use of this method can effectively improve its collection efficiency and conductive performance.

[0028] The rubrene single crystal in S1 is grown by physical vapor transport in nitrogen at 0.1 atmospheres, and the growth thickness of the rubrene single crystal is in the range of 2-5 μm.

[0029] In this embodiment, in nitrogen at 0.1 atmospheres, it can effectively reduce the collision frequency of gas molecules, thereby improving the efficiency of vapor transmission, and in this low-pressure environment, it can also promote the uniform deposition of materials, making the growth rate more controllable. Specifically, refer to the formula PV=nRT, where P is the pressure of the gas, V is the volume of the gas, n is the amount of gas substance, R is the gas constant, and T is the absolute temperature. The above formula expresses that under low pressure conditions, the ideal gas state equation can be used to describe the behavior of the gas, and the comprehensive growth rate formula v=k·(P s -P a ), where v is the growth rate, k is the growth rate constant, and the value of rubrene single crystal is directly inserted here, P s is the vapor pressure of the source material, P a is the gas pressure in the growth environment, and we combine it with Fick's first law formula for vapor transmission rate where J is the net flux, D is the diffusion coefficient, It is the concentration gradient. Based on the above, it can be known that the diffusion of gas and the transmission efficiency of vapor under low pressure conditions are improved, which affects the growth rate and the final thickness range. Therefore, the growth thickness of the rubrene single crystal should be set within 2-5μm.

[0030] The low evaporation rate in S1 is specifically 3-3.3×10-3nm / s at room temperature. -1 Evaporation at a rate of .

[0031] In this embodiment, because a lower evaporation rate means a relatively lower nucleation rate, we set the low evaporation rate to 3-3.3×10-3nm / s -1This can promote the growth of crystals to form larger and more uniform crystals, thereby avoiding the formation of small crystals. The room temperature should be 20°C to 25°C, and the slower evaporation rate also reduces the movement speed of molecules in the gas phase, thereby reducing crystal defects caused by violent collisions and improving the yield of the preparation scheme.

[0032] The preset method in S2 is to add Fe2Cl6 and Cs2CO3 at a doping concentration of 1:10ppm corresponding to 3-3.3×10-8 and 3-3.3×10-7nm / s-1 The doping is performed at a dopant evaporation rate of , and the preset method is achieved by using a slit rotating disk with an aperture ratio of 1:100 to reduce the evaporation rate.

[0033] In this embodiment, low-concentration doping can effectively improve the conductivity of the rubrene film, and through experiments we found that 1:10ppm will not cause many defects in the rubrene film. If the doping concentration is between 1:100ppm and 1:1000ppm, it will lead to increased scattering between carriers inside the rubrene film, thereby reducing its electron mobility. When the doping concentration exceeds 1:500ppm, it can be clearly observed that the crystal structure of the rubrene film is distorted, and the overall structure will have problems such as stress concentration, affecting the overall performance and stability of the material.

[0034] The specific thickness of the rubrene film in S2 is 10-15 nm, and the lateral gap between the two electrodes in S2 is maintained at 0.05-1 mm.

[0035] In this embodiment, we express various characteristics of rubrene films of different thicknesses in a table:

[0036]

[0037]

[0038] Moreover, the test of this value is also applicable to the luminous efficiency, electrical conductivity and carrier mobility of rubrene film. Therefore, we set the specific thickness of rubrene film to 10-15nm. Within the gap range of 0.05-1mm, it can ensure that the current is evenly distributed between the electrodes, avoiding the influence of the carrier on the performance of rubrene film due to excessively high local current density and reducing the electrode gap.

[0039] The p-type homoepitaxial layer in S2 can serve as a lateral hole transport layer.

[0040] In this embodiment, the concept of using the p-type homoepitaxial layer as a lateral hole transport layer is to utilize its good electrical characteristics to ensure effective transport of holes in the rubrene film, thereby achieving more efficient photoelectric conversion.

[0041] The width of the pn homojunction in S2 is the width of the Ag electrode, which is maintained at 2-3 mm. The area of ​​the pn homojunction is 2-3 mm×L mm, where L represents the length of the pn homojunction and the value of L fluctuates between 0.1 and 1.0 mm. The ohmic electrode in contact with the p layer in S2 is a pure hole device.

[0042] In this example, the low exciton dissociation efficiency / ηED can be attributed to the relatively low electric field in the gradually depleted layer of finite width formed at the pn homojunction, which is mainly due to the low doping concentration in its original method. Therefore, we believe that by using a donor / acceptor heterojunction accompanied by an abrupt electrostatic potential gradient, ηED will be increased, and the long exciton diffusion length in organic single crystals can eliminate the need for a mixed junction.

[0043] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for preparing a single crystal photovoltaic cell, characterized in that: include: S1, starting to grow a rubrene single crystal, placing the rubrene single crystal on a red core single crystal substrate after the growth is completed, using a vacuum evaporator to perform low evaporation rate deposition on the grown rubrene single crystal, and then the rubrene single crystal will grow a homoepitaxial film of the red core on the red core single crystal substrate, and then doping is performed by a co-evaporation method; S2, Fe2Cl6 and Cs2CO3 were used as acceptor and donor dopants respectively for doping in a preset method, and then the p-type Fe2Cl6 and Cs2CO3 with a doping concentration of 10000ppm were added. + and n ± Rubrene film is inserted into the Ag electrode and p - and n - type crystals to form an ohmic contact. At this time, by using p + The Ag electrode forms an ohmic contact with the p-type rubrene single crystal to complete the preparation.

2. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The rubrene single crystal in S1 is grown by physical vapor transport in nitrogen at 0.1 atmospheres, and the growth thickness of the rubrene single crystal is in the range of 2-5 μm.

3. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The low evaporation rate of S1 is 3-3.3×10-3nm / s at room temperature. -1 Evaporation at a rate of .

4. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The preset method in S2 is to use Fe2Cl6 and Cs2CO3 at a doping concentration of 1:10ppm corresponding to 3-3.3×10-8 and 3-3.3×10-7nm / s-1 The dopant evaporation rate is used for doping, and the preset method uses a slit rotating disk with an aperture ratio of 1:100 to reduce the evaporation rate.

5. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The thickness of the rubrene film in S2 is 10-15 nm, and the p + The lateral gap between the Ag electrode is 0.05-1mm.

6. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The p-type homoepitaxial layer in S2 serves as a lateral hole transport layer.

7. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The width of the pn homojunction in S2 is the width of the Ag electrode, which is 2-3 mm. The area of ​​the pn homojunction is 2-3 mm×L mm, where L represents the length of the pn homojunction and the value of L is between 0.1-1.0 mm.

8. The method for preparing a single crystal photovoltaic cell according to claim 1, characterized in that: The ohmic electrode in contact with the p-layer in S2 is a pure hole device.

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