Method for realizing efficient carrier transport of antimony selenide solar cell by using wide-band-gap seed crystal layer

Abstract

The invention provides a method for realizing efficient carrier transport of an antimony selenide solar cell through a wide-band gap seed crystal layer. The wide-band-gap Sb2 (S, Se) 3 seed crystal layer is introduced to the CdS / Sb2Se3 heterojunction interface to assist the vertical growth of the Sb2Se3 nanobelt, and the S element is introduced to the heterojunction interface to broaden the heterojunction interface band gap, so that the heterojunction interface reaction is effectively inhibited. Compared with the Sb2S3 seed layer and the Sb2Se3 seed layer which are widely adopted at present, the Sb2 (S, Se) 3 seed layer is more favorable for considering orientation and interface band gap matching, so that the carrier transport of the device is promoted, and meanwhile, the open-circuit voltage of the device is increased.

Description

Technical Field

[0001] The invention belongs to the field of preparation of antimony selenide solar cells, and in particular relates to a method for realizing high-efficiency carrier transport of antimony selenide solar cells with a wide bandgap seed crystal layer. Background Art

[0002] Thin-film solar cells have become an important branch of solar cells due to their low cost, light weight, flexibility, shape plasticity, and good low-light performance. At present, compared with the already industrialized copper indium gallium selenide (Cu(In,Ga)Se2) and cadmium telluride (CdTe) solar cells, as well as high-efficiency perovskite solar cells, Sb2Se3 materials are considered to be highly potential alternative photovoltaic materials due to their low cost, low toxicity, and high stability, and have developed rapidly in recent years. To date, the energy conversion efficiency of Sb2Se3 solar cells based on the vacuum method and the non-vacuum method has reached 10.13% and 10.57%, respectively, but there is still a large gap between traditional photovoltaic cells and their theoretical efficiency values, which can be mainly attributed to their severe open-circuit voltage loss. According to V OC (deficit) = Eg / q–V OC According to the open circuit voltage calculation principle, the current highest efficiency Sb2Se3 solar cell still has an open circuit voltage loss of 0.733 V, which is much larger than the 0.350 V of CIGS and the 0.297 V of CZTSSe, indicating that the loss of open circuit voltage is still one of the main factors limiting the efficiency improvement of Sb2Se3 solar cells. The open circuit voltage loss is mainly composed of several factors such as carrier lifetime, band arrangement, deep energy level defects, P type doping, orientation regulation, band tail states and interface problems. Among them, band arrangement and orientation regulation are the key factors that currently lead to serious open circuit voltage loss in Sb2Se3 solar cells. The "cliff" type conduction band arrangement will cause the carrier lifetime at the interface to be drastically shortened, so the V OC The loss is large. However, the "spike" conduction band arrangement is beneficial to suppress defect recombination, promote carrier separation and transmission efficiency, and reduce the open circuit voltage loss of solar cells. Sb2Se3 has an orthorhombic crystal structure. In the crystal structure, Sb atoms are combined with Se atoms through strong covalent bonds to form [Sb4Se6] extending along the

[001] direction. n Quasi-one-dimensional nanoribbons, in fully (hk0)-oriented films, (Sb4Se6) nThe bands are parallel to the substrate surface, and the interaction between the atoms between the bands is weak, which leads to the loss of electron transport performance in the device. Extensive studies have shown that minimizing the (hk0) orientation is beneficial to improving the efficiency of Sb2Se3 solar cells. Therefore, films with a higher proportion of vertical lattice orientation have better charge transport performance. At present, most of the high-performance Sb2Se3 solar cells use CdS as the contact layer material, and the special quasi-one-dimensional lattice structure makes high-quality Sb2Se3 films have high selectivity for the substrate. Therefore, it is difficult to achieve the coordinated construction of the (001) orientation and band gradient of Sb2Se3 films in the case that the CdS / Sb2Se3 heterojunction interface is prone to element interdiffusion. Seed layer epitaxial induction, as an effective means to improve the performance of Sb2Se3 solar cells, shows great potential. At present, most researchers use Sb2S3 or Sb2Se3 as a seed layer to assist the growth of Sb2Se3 films. Using Sb2S3 as a seed layer is beneficial to suppressing the CdS / Sb2Se3 heterojunction interface reaction, but the orientation of Sb2Se3 is difficult to control; using Sb2Se3 as a seed layer is easy to control the growth orientation of Sb2Se3 film, but it is easy to cause CdS / Sb2Se3 heterojunction interface reaction during the subsequent deposition of antimony selenide. Summary of the invention

[0003] The purpose of the present invention is to provide a method for realizing high-efficiency carrier transport of antimony selenide solar cells with a wide bandgap seed crystal layer.

[0004] In view of the above problems, the present invention solves the following two technical problems: (1) A synergistic scheme of using sulfur-rich Sb2(S,Se)3 seed layer to improve the vertical growth orientation and energy band alignment of Sb2Se3 thin films is proposed.

[0005] (2) Reveal the intrinsic mechanism of the seed layer to suppress the open-circuit voltage loss of Sb2Se3 solar cells and improve the conversion efficiency of the device.

[0006] The Sb2(S,Se)3 seed layer has the following advantages: 1) It can largely suppress the heterojunction interface reaction; 2) The introduction of selenium components improves the (hk1) orientation of antimony sulfide in the seed layer; 3) The sulfur-rich components are conducive to widening the band gap at the heterojunction interface and improving the open circuit voltage of the device. The synergistic construction of the 001 orientation and band gradient of the Sb2Se3 film can also suppress the mutual diffusion of elements at the heterojunction interface.

[0007] To achieve the above object, the present invention adopts the following technical solution: (1) FTO glass treatment: After scrubbing the FTO glass with detergent water, ultrasonically clean it with ethanol, acetone, and deionized water respectively, blow dry it with an air gun, and put it in a drying oven for later use; (2) Deposition of CdS film: CdSO4, ammonia and deionized water were mixed, preheated at 66 °C for 2 min, then thiourea was added and placed on FTO glass. After deposition at 66 °C for 22 min, the film was taken out and blown dry. (3) CdCl2 treatment: CdCl2 was mixed with methanol, and then the CdCl2 solution was spin-coated on the CdS film on a coating machine. The film was then placed on a hot plate at 400 °C for air annealing for 11 min, and then removed from the hot plate after free cooling. (4.1) Preparation of Sb2(S,Se)3 seed layer by VTD method: After cleaning the tube, put in the treated glass substrate, 0.008g Sb2S3 powder, and 0.02g Sb2Se3 powder, put in the cover and graphite baffle, make sure the vent is closed, turn on the vacuum pump, fill the quartz tube with inert gas and maintain a pressure of 100Pa, start the tube furnace, and set the tube furnace program to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to 100℃, then take out the glass sheet; (4.2) Preparation of Sb2Se3 thin film by VTD method: Place 0.02g Sb2Se3 powder and the substrate with the seed layer deposited, put in the cover, bottom support, and graphite baffle, make sure the vent is closed, turn on the vacuum pump, maintain the vacuum pressure condition of 0.2Pa, start the tube furnace, and set the tube furnace program to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to 100℃, then take out the glass sheet; (5) Preparation of Spiro-OMeTAD hole transport layer: The spin coater was set to single-step operation mode, with a rotation speed of 3500 rpm, a time of 30 s, and an acceleration of 1000 rpm / s. 20 uL of 36.6 mg / mL Spiro-OMeTAD solution was dripped onto the sample. After spin coating, the sample was annealed on a hot plate at 105 °C for 10 min. (6) Evaporation of Au electrode: The gold electrode is prepared by thermal evaporation. The mask is placed in the evaporation machine and the Au evaporation program is run. Finally, the surface of the device is divided into two sections with the same effective area of ​​0.09 cm 2 of small squares.

[0008] The advantages of the present invention are: The invention introduces a wide bandgap Sb2(S,Se)3 seed layer at the CdS / Sb2Se3 heterojunction interface to assist the vertical growth of Sb2Se3 nanoribbons, and introduces S elements at the heterojunction interface to widen the heterojunction interface bandgap, thereby effectively inhibiting heterojunction interface reaction. Compared with the currently widely used Sb2S3 and Sb2Se3 seed layers, the Sb2(S,Se)3 seed layer is more conducive to taking into account both orientation and interface bandgap matching, thereby promoting carrier transport of the device while increasing the open circuit voltage of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 a) JV curve under AM 1.5G irradiation, b) EQE spectrum; Figure 2 a) Seed layer film, b) SEM image of Sb2Se3 film, c) XRD pattern of seed layer film and Sb2Se3 film. DETAILED DESCRIPTION

[0010] In order to make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0011] Example 1 (1) FTO glass treatment: Scrub the FTO glass with detergent and water and put it into a beaker. Ultrasonicate it with detergent, ethanol, acetone, and deionized water for 30 min respectively, blow it dry with an air gun, and put it into a drying oven for later use.

[0012] (2) Deposition of CdS film: 32 mL of 15 mM CdSO4 solution, 40 mL of 28 wt% ammonia water and 220 mL of deionized water were placed in a beaker, preheated in a 66 °C water bath for 2 min, then 16 mL of 1.5 mM thiourea aqueous solution was added and placed in the FTO glass. After deposition in a 66 °C water bath for 22 min, the beaker was taken out and blown dry.

[0013] (3) CdCl2 treatment: 15 mg CdCl2 was mixed with 1 mL methanol, and then the CdCl2 solution was spin-coated on the CdS film on a spunbond. Then, the film was air-annealed on a hot plate at 400 °C for 11 min, and then removed from the hot plate after free cooling.

[0014] (4.1) Preparation of Sb2(S,Se)3 seed layer by VTD method: After cleaning the tube, put in the treated glass substrate, 0.008g Sb2S3 powder, and 0.02g Sb2Se3 powder, put in the cover and graphite baffle, make sure the vent is closed, turn on the vacuum pump, fill the quartz tube with inert gas and maintain a pressure of 100Pa, and start the tube furnace. The tube furnace program is set to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to about 100℃, then take out the glass sheet.

[0015] (4.2) Preparation of Sb2Se3 thin film by VTD method: Place 0.02g Sb2Se3 powder and the substrate with the seed layer deposited, put in the cover, bottom support, and graphite baffle, make sure the vent is closed, turn on the vacuum pump, maintain the vacuum pressure condition of 0.2Pa, and start the tube furnace. The tube furnace program is set to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to about 100℃, then take out the glass sheet.

[0016] (5) Preparation of Spiro-OMeTAD hole transport layer: The spin coater was set to single-step operation mode, with a rotation speed of 3500 rpm, a time of 30 s, and an acceleration of 1000 rpm / s. 20 uL of 36.6 mg / mL Spiro-OMeTAD solution was dripped onto the sample. After spin coating, the sample was annealed on a hot plate at 105 °C for 10 min.

[0017] (6) Evaporation of Au electrode: The gold electrode is prepared by thermal evaporation. The mask is placed in the evaporation machine and the Au evaporation program is run. Finally, the surface of the device is divided into two sections with the same effective area of ​​0.09 cm 2 of small squares.

[0018] Comparative Example 1 (1) FTO glass treatment: Scrub the FTO glass with detergent and water and put it into a beaker. Ultrasonicate it with detergent, ethanol, acetone, and deionized water for 30 min respectively, blow it dry with an air gun, and put it into a drying oven for later use.

[0019] (2) Deposition of CdS film: 32 mL of 15 mM CdSO4 solution, 40 mL of 28 wt% ammonia water and 220 mL of deionized water were placed in a beaker, preheated in a 66 °C water bath for 2 min, then 16 mL of 1.5 mM thiourea aqueous solution was added and placed in the FTO glass. After deposition in a 66 °C water bath for 22 min, the beaker was taken out and blown dry.

[0020] (3) CdCl2 treatment: 15 mg CdCl2 was mixed with 1 mL methanol, and then the CdCl2 solution was spin-coated on the CdS film on a spunbond. Then, the film was air-annealed on a hot plate at 400 °C for 11 min, and then removed from the hot plate after free cooling.

[0021] (4) Preparation of Sb2Se3 thin film by VTD method: Place 0.02g Sb2Se3 powder and CdCl2 treated substrate, put in the cover, bottom support, and graphite baffle, confirm that the vent is closed, turn on the vacuum pump, maintain the vacuum pressure condition of 0.2Pa, and start the tube furnace. The tube furnace program is set to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to about 100℃, then take out the glass sheet.

[0022] (5) Preparation of Spiro-OMeTAD hole transport layer: The spin coater was set to single-step operation mode, with a rotation speed of 3500 rpm, a time of 30 s, and an acceleration of 1000 rpm / s. 20 uL of 36.6 mg / mL Spiro-OMeTAD solution was drawn with a pipette and dropped onto the sample. After spin coating, the sample was annealed on a hot plate at 105 °C for 10 min.

[0023] (6) Evaporation of Au electrode: The gold electrode is prepared by thermal evaporation. The mask is placed in the evaporation machine and the Au evaporation program is run. Finally, the surface of the device is divided into two sections with the same effective area of ​​0.09 cm 2 of small squares.

[0024] Sb2Se3 has achieved a conversion efficiency of over 10% due to its excellent photoelectric properties. However, the difficult-to-control lattice orientation and heterojunction interface reaction lead to severe open circuit voltage loss (V OC -deficit), thus limiting the further improvement of its conversion efficiency. The present invention introduces a wide-bandgap Sb2(S,Se)3 seed layer at the CdS / Sb2Se3 heterojunction interface to assist the vertical growth of Sb2Se3 nanoribbons, and introduces the S element at the heterojunction interface to widen the heterojunction interface band gap, thereby effectively inhibiting the heterojunction interface reaction. Compared with the currently widely used Sb2S3 and Sb2Se3 seed layers, the Sb2(S,Se)3 seed layer is more conducive to taking into account both orientation and interface band gap matching, thereby promoting carrier transport in the device while increasing the open circuit voltage of the device. In addition, the preparation of the seed layer is achieved by in-situ working gas pressure regulation. The diffusion length of the vapor molecules is regulated in situ by changes in gas pressure, thereby achieving component regulation of the deposition area under different working pressures. Figure 1As shown in the JV results in (a), the short-circuit current density and open-circuit voltage of the device were significantly improved after the introduction of the seed layer, and the conversion efficiency of the Sb2Se3 solar cell was finally increased from 7.03% to 7.56%. Figure 1 From the external quantum efficiency results in (b), we can see that the introduction of the seed layer can improve the quantum response of short waves below 600 nm. This may be the result that the introduction of the wide bandgap seed layer widens the band gap of the device's front interface and optimizes the heterojunction quality, thereby effectively suppressing the non-radiative recombination losses at the front interface. In the long-wave region greater than 750 nm, the external quantum response of TFSC-90s is worse than that of TFSC-C, indicating that the non-radiative recombination of carriers at the back interface is more serious. From the analysis results of the above SEM and JV characteristics, it can be seen that the introduction of the seed layer can effectively improve the carrier transport performance of the device. In order to analyze the intrinsic reasons for the enhanced carrier transport, X-ray diffraction analysis of the sample seed layer film and Sb2Se3 film was carried out here, and the results are shown in the figure. Figure 2 As shown in b. By comparing with the standard PDF card of Sb2Se3 film (PDF#72-1184), it is found that the Sb2Se3 film has an obvious preferential trend on the (002) crystal plane diffraction peak, so the introduction of the seed layer is conducive to the growth of the preferred orientation of the Sb2Se3 film (hkl,l=1).

[0025] Table 1 Performance parameters of Sb2Se3 solar cells with and without seed layer induced growth The results show that the introduction of the wide-bandgap Sb2(S,Se)3 seed layer enables the preparation of highly (001) oriented Sb2Se3 thin films; widens the heterojunction interface band gap, achieves a "Spike" conduction band arrangement that is beneficial to carrier transport; widens the depletion region width of the solar cell, and significantly improves the quality of the CdS / Sb2Se3 heterojunction and the carrier transport performance of its devices. Finally, the antimony selenide solar cell induced by the wide-bandgap Sb2(S,Se)3 seed layer achieved a PCE of 7.56%. It is worth noting that the V of the TFSC-90s device OC It reached 466 mV, which is the highest value of Sb2Se3TFSCs in VTD process so far. This will promote the industrialization of low-cost antimony sulfide selenide compound thin film solar cells and provide valuable reference for the interface and orientation regulation of antimony-based chalcogenide compound solar cells.

[0026] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for realizing high-efficiency carrier transport of antimony selenide solar cells with a wide bandgap seed layer, characterized in that: The following steps are involved: (1) FTO glass cleaning; (2) Deposition of CdS thin film; (3) CdCl2 treatment: CdCl2 was mixed with methanol, and then the CdCl2 solution was spin-coated on the CdS film on a coating machine. The film was then placed on a hot plate at 400 °C for air annealing for 11 min, and then removed from the hot plate after free cooling. (4.1) Preparation of Sb2(S,Se)3 seed layer by VTD method: After cleaning the tube, put in the treated glass substrate, 0.008g Sb2S3 powder, and 0.02g Sb2Se3 powder, put in the cover and graphite baffle, make sure the vent is closed, turn on the vacuum pump, fill the quartz tube with inert gas and maintain a pressure of 100Pa, start the tube furnace, and set the tube furnace program to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to 100℃, then take out the glass sheet; (4.2) Preparation of Sb2Se3 thin film by VTD method: Place 0.02g Sb2Se3 powder and the substrate with the seed layer deposited, put in the cover, bottom support, and graphite baffle, make sure the vent is closed, turn on the vacuum pump, maintain the vacuum pressure condition of 0.2Pa, start the tube furnace, and set the tube furnace program to increase the temperature from room temperature to 540℃ within 11 minutes and 30 seconds and keep it warm for 90 seconds; after the program is completed, open the furnace and cool it down to 100℃, then take out the glass sheet; (5) Preparation of Spiro-OMeTAD hole transport layer; (6) Evaporation of Au electrode.

2. The preparation method according to claim 1, characterized in that: The operation of cleaning the FTO glass in step (1) specifically includes: scrubbing the FTO glass with detergent water, ultrasonically cleaning it with ethanol, acetone, and deionized water respectively, then drying it with an air gun, and placing it in a drying oven for standby use.

3. The preparation method according to claim 1, characterized in that: The operation of depositing the CdS film in step (2) specifically includes: mixing CdSO4, ammonia water and deionized water, preheating for 2 minutes, then adding thiourea, and placing FTO glass, depositing the CdS film at 66°C, taking it out and blowing it dry for later use.

4. The preparation method according to claim 3, characterized in that: The preheating temperature in step (2) is 66°C.

5. The preparation method according to claim 3, characterized in that: The deposition time in step (2) is 22 min.

6. The preparation method according to claim 1, characterized in that: The preparation of the Spiro-OMeTAD hole transport layer in step (5) specifically includes: setting the spin coater to a single-step operation mode, with a rotation speed of 3500 rpm, a time of 30 s, and an acceleration of 1000 rpm / s; using a pipette to extract 20 uL of the prepared Spiro-OMeTAD solution, dripping it onto the sample, and after spin coating, annealing on a hot stage.

7. The preparation method according to claim 6, characterized in that: The annealing temperature in step (5) is 105°C.

8. The preparation method according to claim 6, characterized in that: The annealing time in step (5) is 10 min.

9. The preparation method according to claim 1, characterized in that: In step (6), the Au electrode is prepared by thermal evaporation, the mask is placed in the evaporation machine, and the Au evaporation program is run.

10. The preparation method according to claim 1, characterized in that: The shape of the Au electrode in step (6) is 0.09 cm 2 of small squares.

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