A method for preparing CuGaO2 solar cell

Abstract

The present invention discloses a method for preparing a CuGaO2 solar cell. Using NaHCO3 and Ga(NO3)3·9H2O as sodium and gallium sources, a solvent-free reaction method combining low temperature and high temperature is adopted to synthesize β-NaGaO2. β-NaGaO2 is ion-exchanged with CuCl to obtain pure-phase β-CuGaO2. β-CuGaO2 is mixed with oxide buffer layer powder, ground, and then scraped onto a buffer layer film to construct an embedded battery. The present invention adopts a solvent-free reaction method combining low temperature and high temperature to prepare the intermediate product β-NaGaO2, which has a larger reaction contact area, achieves better mass transfer, greatly reduces reaction time and temperature, and reduces energy consumption. At the same time, an embedded structure is used to prepare the battery, and a photovoltaic device with an efficiency of 0.037% is obtained, which solves the problem that it is difficult to construct a planar structure device due to material properties.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell materials and devices, and in particular to a method for preparing a CuGaO2 solar cell. Background Art

[0002] Since the Industrial Revolution, the energy used by mankind has been mainly fossil energy such as coal and oil. Fossil energy is a non-renewable energy source. As time goes by, the depletion of fossil energy is inevitable and will pollute the environment. Therefore, it has become a top priority to find clean and renewable energy to replace fossil energy and maintain the sustainable development of energy, and solar energy is one of the clean and renewable energy sources. Solar cells can be divided into three categories: one is single crystal silicon and polycrystalline silicon solar cells, another is new solar cells such as perovskites and quantum dots, and another is thin-film solar cells based on multi-inorganic compound thin films. Thin-film solar cells have a thinner thickness and excellent stability, which is conducive to the preparation of flexible devices and can be applied to more scenarios. Among them, mature thin-film solar cells such as copper indium gallium selenide and cadmium telluride have an efficiency of more than 20%. CuGaO2 with a wurtzite structure is an ideal thin-film solar cell absorption layer material. It has a direct narrow band gap of 1.47 eV. The band gap width matches the band gap required to achieve the theoretical maximum conversion efficiency in a single-junction solar cell, and has a high absorption coefficient (10 5 cm -1 ), good stability, and the Cu, Ga, and O elements it contains are green and non-toxic. These properties make this new material suitable as an absorption layer material in solar cells.

[0003] The main phases of CuGaO2 are α-CuGaO2 with delafossite structure and β-CuGaO2 with wurtzite structure. Although they have the same composition and are both P-type semiconductors, α-CuGaO2 has a wider band gap (3.58 eV), a suitable valence band maximum position (-5.29 eV), and a high hole mobility (10 -2 ~10 1 cm 2 V -1 s -1), which is more suitable as a hole transport layer (HTL) material (Advanced Materials. 2017, 29 (8).). β-CuGaO2 with a wurtzite structure is more suitable as an absorber material, but it is a metastable phase and easily undergoes a phase transition to α-CuGaO2 at high temperatures. According to a search of the prior art, no relevant reports on solar cells using β-CuGaO2 as an absorber layer have been found, and even the relevant information on the synthesis of β-CuGaO2 materials is very limited. By searching the existing literature, it was found that the earliest synthesis of β-CuGaO2 powder was reported in 2014. β-NaGaO2 was obtained by mixing Na2CO3 and Ga2O3 and sintering at 900℃ for 20 hours. The mixture was then mechanically mixed with CuCl and ion exchanged at 250℃ for 48 hours to prepare β-CuGaO2 (Journal of the American Chemical Society, 2014, 136(9)). However, due to the large particle size of the raw materials Na2CO3 and Ga2O3, the mass transfer was poor in the high-temperature solid-phase reaction, resulting in the reaction requiring a higher temperature and a longer time.

[0004] In addition, in device research, Takahisa Omata's group obtained β-NaGaO2 thin films by magnetron sputtering, and then obtained β-CuGaO2 thin films by replacing Na with Cu in a CuCl gas atmosphere (Applied Physics Express, 2017, 10 (9).); or they first prepared β-NaGaO2 by the sol-gel method, and also obtained β-CuGaO2 thin films by ion exchange with CuCl, and tried to build devices, but there was no photoelectric response (Emergent Materials, 2023, 6, 167-174). The films prepared by these methods produced cracks due to lattice shrinkage during ion exchange. In thin-film solar cells, cracks in the films affect carrier transport, so there are currently no reports on β-CuGaO2 solar cells. Summary of the Invention

[0005] The present invention aims to provide a method for preparing low-energy, embedded-structure CuGaO2 solar cells. The method involves mixing and grinding Ga(NO3)3·9H2O, NaHCO3, and NH4HCO3 to form a Na-Ga precursor. This is then followed by a high-temperature solid-phase reaction to form β-NaGaO2. This ion exchange reaction then synthesizes β-CuGaO2. The synthesized β-CuGaO2 is then mixed with an oxide buffer layer material, ground, and then coated onto the buffer layer to prepare the cell. This method significantly reduces reaction temperature and time, while also addressing the difficulty of constructing traditional planar-structured devices with β-CuGaO2.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a CuGaO2 solar cell comprises the following steps:

[0008] 1) Mix and grind Ga(NO3)3·9H2O, NaHCO3 and NH4HCO3 to obtain a precursor, and then sinter the precursor at high temperature to obtain the intermediate product β-NaGaO2;

[0009] 2) ion exchange β-NaGaO2 with CuCl to obtain β-CuGaO2;

[0010] 3) An oxide buffer layer film was prepared on clean SnO2-coated FTO glass using a sol-gel method. The above-mentioned β-CuGaO2 was mixed with buffer layer powder and adhesive and ground into a colloidal mixture. The colloidal mixture was coated on the above-mentioned oxide buffer layer film using a doctor blade method. After annealing, a layer of carbon was brushed on as an electrode to obtain an embedded structure battery.

[0011] In step 1), the molar ratio of Ga(NO3)3·9H2O, NaHCO3 and NH4HCO3 is 1:1:5~10.

[0012] In step 1), the sintering temperature is 700-900° C. and the sintering time is 0.5-6 hours.

[0013] In step 2), the ion exchange temperature is 250° C. and the time is 12 to 48 hours.

[0014] In step 3), the oxide buffer layer is coated on FTO by a sol-gel method. Specifically, a) 1.00 mL of tetrabutyl titanate, 0.33 mL of acetylacetone and 11.67 mL of anhydrous ethanol are mixed and stirred for 2 h to obtain a TiO2 solution; b) 0.275 mL of ethanolamine and 1 g of zinc acetate are dissolved in 10 mL of ethylene glycol methyl ether and stirred for 2 h to obtain a ZnO solution; c) the TiO2 solution and the ZnO solution are mixed to obtain a TiO2 / ZnO solution, and then the TiO2 / ZnO solution is spin-coated on the FTO at a speed of 7000~7500 rpm for 15 s and annealed at 500 ° C for 30~35 min.

[0015] In step 3), the buffer layer powder is TiO2, ZnO, etc.

[0016] In step 3), the binder is prepared by dissolving 1 g of ethyl cellulose in 10 mL of terpineol and stirring in a 70° C. water bath for 6 to 12 hours.

[0017] In step 3), the coating thickness of the colloidal mixture is 20-30 μm.

[0018] This invention adopts the above technical solution, replacing Ga2O3 with Ga(NO3)3·9H2O, which has a lower hardness, and Na2CO3 with NaHCO3, which is more easily decomposed, to reduce the reaction difficulty. NH4HCO3 is also added to aid grinding. A room-temperature pre-reaction forms a precursor containing Na-Ga, which is then subjected to a high-temperature solid-phase reaction to synthesize β-NaGaO2. This solves the problem of poor mass transfer between large particles with a smaller specific surface area in solid-solid reactions, significantly reducing reaction time (as low as 30 minutes) and temperature (as low as 700°C). Furthermore, the device structure is optimized, abandoning the traditional planar structure and innovatively proposing a device with an embedded absorber layer. An oxide buffer layer material (such as TiO2 or ZnO) and an absorber layer material (β-CuGaO2) are mixed and ground, mixed with a binder, and then coated on a substrate. This creates a molecular-level heterojunction between the TiO2 and β-CuGaO2, forming an oxygen atom-shared interface, enabling efficient carrier transport and generating a photoelectric response for the first time. The resulting device achieves a photoelectric conversion efficiency of 0.037%.

[0019] The principles of the present invention are: 1) Small-particle Ga(NO3)3·9H2O and easily decomposable NaHCO3 are used as sodium and gallium sources to prepare NaGaO2, which increases the specific surface area, reduces the reaction energy barrier and time, and produces a pre-reaction during mixing and grinding to form a precursor containing Na-Ga, which is then obtained through a high-temperature solid-phase method. 2) When preparing β-CuGaO2 batteries, small-particle oxide buffer layer powder is mixed with β-CuGaO2 and ground and coated to prepare an embedded structure battery, constructing a molecular-level PN junction.

[0020] The present invention proposes a method for preparing a low-energy, embedded-structure β-CuGaO2 solar cell. The prior art process for synthesizing β-CuGaO2 suffers from long reaction times and high reaction temperatures. Due to the high-temperature phase transition characteristics of the material and the lattice shrinkage during the ion exchange process, it is difficult to obtain high-quality β-CuGaO2 thin films. Therefore, the present invention employs a solvent-free reaction method combining low and high temperatures to prepare the intermediate product, β-NaGaO2, and simultaneously employs an embedded structure to prepare the cell, resulting in a photovoltaic device with an efficiency of 0.037%. The present invention has the following beneficial effects:

[0021] 1) The intermediate product β-NaGaO2 is prepared by a solvent-free reaction method combining low temperature and high temperature, which has a larger reaction contact area, achieves better mass transfer, greatly reduces reaction time and temperature, and reduces energy consumption.

[0022] 2) This invention is the first to use an embedded structure to construct a β-CuGaO2 solar cell, solving the problem of difficulty in constructing a planar structure device due to material properties, and achieving a breakthrough in the development of β-CuGaO2 solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the XRD pattern of the β-CuGaO2 powder prepared in Example 1 of the present invention.

[0024] Figure 2 This is the JV curve of the β-CuGaO2 battery prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] In the following examples, chemical reagents were purchased from Sinopharm Chemical Reagent Company, and the FTO glass substrates involved were purchased from Liaoning Youxuan Co., Ltd. Example

[0027] A method for preparing a CuGaO2 solar cell comprises the following steps:

[0028] 1) Ga(NO3)3·9H2O, NaHCO3, and NH4HCO3 in a molar ratio of 1:1:7 were placed in a mortar and ground for 30 minutes to obtain a precursor. The precursor was reacted at 700°C for 30 minutes to generate β-NaGaO2.

[0029] 2) Grind β-NaGaO2 and CuCl for 10 minutes, perform ion exchange at 250°C for 12 hours under vacuum, and then wash and dry to obtain β-CuGaO2.

[0030] 3) Immerse the FTO glass substrate in detergent, acetone, ethanol, and deionized water in sequence and perform ultrasonic cleaning for 30 minutes each;

[0031] An oxide buffer layer was prepared on a glass substrate using a sol-gel method as follows: a) 1.00 mL of tetrabutyl titanate, 0.33 mL of acetylacetone, and 11.67 mL of anhydrous ethanol were mixed and stirred for 2 h to obtain a TiO2 solution; b) 0.275 mL of ethanolamine and 1 g of zinc acetate were dissolved in 10 mL of ethylene glycol methyl ether and stirred for 2 h to obtain a ZnO solution; c) the TiO2 solution and the ZnO solution were mixed to obtain a TiO2 / ZnO solution, which was then spin-coated on FTO at a speed of 7000 rpm for 15 s and annealed at 500°C for 30 min.

[0032] After grinding β-CuGaO2 with oxide buffer layer powder (TiO2) and a binder (1g ethyl cellulose dissolved in 10mL terpineol and stirred in a 70°C water bath for 8h) for 12h, a colloidal mixture was obtained. The colloidal mixture was coated on the above-mentioned oxide buffer layer film by a doctor blade method. After annealing at 250°C for 10min, an embedded structure PN junction was obtained. A layer of carbon was then brushed on as an electrode to obtain an embedded structure battery.

[0033] The β-CuGaO2 prepared in this embodiment was tested using XRD. Figure 1 As shown in the standard PDF card, there is no β-CuGaO2 in Jade. Compared with the β-CuGaO2 spectrum of wurtzite obtained by MS calculation, it can be seen that the powder obtained is pure β-CuGaO2 phase. The JV curve under AM1.5G irradiation was obtained using Keithley 2400. Figure 2 It can be seen that the obtained device efficiency is 0.037%. Example

[0034] A method for preparing a CuGaO2 solar cell comprises the following steps:

[0035] 1) Ga(NO3)3·9H2O, NaHCO3, and NH4HCO3 in a molar ratio of 1:1:5 were placed in a mortar and ground for 30 minutes to obtain a precursor. The precursor was reacted at 800°C for 30 minutes to generate β-NaGaO2.

[0036] 2) Grind β-NaGaO2 and CuCl for 15 minutes, perform ion exchange at 250°C under vacuum for 24 hours, and then wash and dry to obtain β-CuGaO2.

[0037] 3) Immerse the FTO glass substrate in detergent, acetone, ethanol, and deionized water in sequence and perform ultrasonic cleaning for 30 minutes each;

[0038] An oxide buffer layer was prepared on a glass substrate using a sol-gel method as follows: a) 1.00 mL of tetrabutyl titanate, 0.33 mL of acetylacetone, and 11.67 mL of anhydrous ethanol were mixed and stirred for 2 h to obtain a TiO2 solution; b) 0.275 mL of ethanolamine and 1 g of zinc acetate were dissolved in 10 mL of ethylene glycol methyl ether and stirred for 2 h to obtain a ZnO solution; c) the TiO2 solution and the ZnO solution were mixed to obtain a TiO2 / ZnO solution, which was then spin-coated on FTO at a speed of 7000 rpm for 15 s and annealed at 500°C for 30 min.

[0039] β-CuGaO2, oxide buffer layer powder (TiO2), and binder (1g ethyl cellulose dissolved in 10mL pinene alcohol, stirred in a 70°C water bath for 10h) were ground for 12h to obtain a colloidal mixture. The colloidal mixture was then coated on the above-mentioned oxide buffer layer film by a doctor blade method. After annealing at 250°C for 10min, an embedded structure PN junction was obtained. A layer of carbon was then applied as an electrode to obtain an embedded structure battery. Example

[0040] A method for preparing a CuGaO2 solar cell comprises the following steps:

[0041] 1) Ga(NO3)3·9H2O, NaHCO3, and NH4HCO3 in a molar ratio of 1:1:10 were placed in a mortar and ground for 30 minutes to obtain a precursor. The precursor was reacted at 900°C for 30 minutes to generate β-NaGaO2.

[0042] 2) Grind β-NaGaO2 and CuCl for 10 minutes, perform ion exchange at 250°C for 12 hours under vacuum, and then wash and dry to obtain β-CuGaO2.

[0043] 3) Immerse the FTO glass substrate in detergent, acetone, ethanol, and deionized water in sequence and perform ultrasonic cleaning for 30 minutes each;

[0044] An oxide buffer layer was prepared on a glass substrate using a sol-gel method as follows: a) 1.00 mL of tetrabutyl titanate, 0.33 mL of acetylacetone, and 11.67 mL of anhydrous ethanol were mixed and stirred for 2 h to obtain a TiO2 solution; b) 0.275 mL of ethanolamine and 1 g of zinc acetate were dissolved in 10 mL of ethylene glycol methyl ether and stirred for 2 h to obtain a ZnO solution; c) the TiO2 solution and the ZnO solution were mixed to obtain a TiO2 / ZnO solution, which was then spin-coated on FTO at a speed of 7000 rpm for 15 s and annealed at 500°C for 30 min.

[0045] β-CuGaO2, oxide buffer layer powder (ZnO), and binder (1g ethyl cellulose dissolved in 10mL terpineol, stirred in a 70°C water bath for 12h) were ground for 12h to obtain a colloidal mixture. The colloidal mixture was then coated on the above-mentioned oxide buffer layer film by a doctor blade method. After annealing at 250°C for 10min, an embedded structure PN junction was obtained. A layer of carbon was then applied as an electrode to obtain an embedded structure battery.

Claims

1. A method for preparing a CuGaO2 solar cell, characterized in that: The following steps are involved: 1) Ga(NO3)3·9H2O, NaHCO3 and NH4HCO3 are mixed and ground to obtain a precursor, and then the precursor is sintered at a high temperature to obtain an intermediate product β-NaGaO2, wherein the sintering temperature is 700~900℃ and the sintering time is 0.5~6h; 2) ion exchange β-NaGaO2 with CuCl to obtain β-CuGaO2; 3) An oxide buffer layer film was prepared on clean SnO2-coated FTO glass using a sol-gel method. The above-mentioned β-CuGaO2 was mixed with buffer layer powder and adhesive and ground into a colloidal mixture. The colloidal mixture was coated on the above-mentioned oxide buffer layer film using a doctor blade method. After annealing, a layer of carbon was brushed on as an electrode to obtain an embedded structure battery.

2. The method for preparing a CuGaO2 solar cell according to claim 1, wherein: In step 1), the molar ratio of Ga(NO3)3·9H2O, NaHCO3 and NH4HCO3 is 1:1:5~10.

3. The method for preparing a CuGaO2 solar cell according to claim 1, wherein: In step 2), the ion exchange temperature is 250° C. and the time is 12 to 48 hours.

4. The method for preparing a CuGaO2 solar cell according to claim 1, wherein: In step 3), the oxide buffer layer is formed by coating a TiO2 / ZnO mixed solution on the FTO glass by a sol-gel method and annealing at 500°C for 30-35 minutes.

5. The method for preparing a CuGaO2 solar cell according to claim 1, wherein: In step 3), the buffer layer powder is TiO2 or ZnO.

6. The method for preparing a CuGaO2 solar cell according to claim 1, wherein: In step 3), the adhesive is a colloid obtained by dissolving ethyl cellulose in terpineol.

7. The method for preparing a CuGaO2 solar cell according to claim 1, wherein: In step 3), the coating thickness of the colloidal mixture is 20-30 μm.

Images