Cadmium-free electron transport layer, antimony-based chalcogenide thin film solar cell and preparation method

Abstract

The invention discloses a cadmium-free electron transport layer, an antimony-based chalcogenide thin film solar cell and a preparation method, and relates to the field of solar cells, and the preparation method of the cadmium-free electron transport layer comprises the following steps: S1, carrying out m times of cyclic deposition of a ZnO monomolecular layer through an atomic layer deposition method, and obtaining a first thin film layer; s2, performing n times of circulating deposition of a SnO2 monomolecular layer on the first thin film layer through an atomic layer deposition method to obtain a second thin film layer; s3, repeating the step S1 to the step S2 for a plurality of times to obtain the cadmium-free electron transport layer; wherein m: n = (1-6): 1, the heterojunction energy band arrangement formed by the cadmium-free electron transport layer and the antimony-based chalcogenide semiconductor presents an ideal peak-shaped configuration, and the corresponding conduction band order value is 0-0.4 eV, so that not only can the aggregation and recombination of photon-generated carriers on an interface be effectively inhibited, but also the efficient separation and transport of the carriers can be ensured.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and in particular to a cadmium-free electron transport layer, an antimony-based sulfur-based thin-film solar cell and a preparation method thereof. Background Art

[0002] Thin-film solar cells have become a research hotspot among a wide variety of photovoltaic cell materials due to their advantages such as low material consumption, high output power, high product scalability and flexibility. At present, the long-term and large-scale development of mainstream high-efficiency thin-film solar cells such as copper indium gallium selenide, cadmium telluride and perovskite is still limited by the natural scarcity, environmental friendliness and long-term stability of raw materials. Based on this, in recent years, antimony-based sulfide thin-film photovoltaic semiconductors (such as Sb2S3, Sb2Se3 and Sb2(S,Se)3) with excellent photoelectric properties such as ideal band gap, high absorption coefficient, good carrier mobility and long carrier lifetime have gradually attracted people's attention, and the corresponding battery efficiency has steadily increased.

[0003] At present, the reported high-efficiency antimony-based sulfur-based thin-film solar cells are mainly based on cadmium sulfide (CdS) as a buffer layer, which plays the role of electron transport layer (ETL). However, the CdS electron transport layer has three major defects: first, CdS contains toxic cadmium elements, which poses safety and environmental risks during device preparation and use; second, the band gap of CdS is relatively low, at 2.4eV, which will absorb some high-energy photons (400-600nm) and cause parasitic current losses; third, during the preparation of CdS, cadmium ions and sulfur ions randomly diffused into the light absorption layer under heat / light treatment may cause device efficiency degradation. At present, candidate electron transport layer materials such as TiO2 and ZnO with cadmium-free and wide-bandgap have shown certain application value in antimony-based sulfur-based thin-film solar cells. However, there are generally undesirable "cliff-like" or excessive "spike-like" conduction band steps between the antimony-based sulfur-based light absorption layer and the electron transport layer such as TiO2 and ZnO. This non-ideal heterojunction band matching seriously hinders the separation and transmission of photogenerated carriers, thus affecting the further improvement of device performance.

[0004] Therefore, key scientific issues such as the selection of environmentally friendly, efficient and stable cadmium-free electron transport layer materials suitable for antimony-based sulfur-based thin-film solar cells and the corresponding heterojunction interface energy band matching regulation need to be urgently addressed.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0006] Based on the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a cadmium-free electron transport layer, an antimony-based sulfide thin-film solar cell and a preparation method, aiming to provide a cadmium-free electron transport layer suitable for antimony-based sulfide thin-film solar cells, so as to solve the problem that the existing electron transport layers such as TiO2 and ZnO and the non-ideal heterojunction energy band matching with antimony-based sulfide semiconductors hinder the separation and transmission of photogenerated carriers.

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

[0008] A first aspect of the present invention provides a method for preparing a cadmium-free electron transport layer, comprising the following steps:

[0009] S1, performing m cycles of ZnO monolayer deposition by atomic layer deposition to obtain a first thin film layer;

[0010] S2, performing n cycles of SnO2 monolayer deposition on the first thin film layer by atomic layer deposition to obtain a second thin film layer;

[0011] S3, repeating steps S1 to S2 several times to obtain the cadmium-free electron transport layer;

[0012] Among them, m:n=(1~6):1.

[0013] Optionally, in step S1, in the m-times cyclic deposition of the ZnO monolayer, the steps of each ZnO monolayer deposition specifically include:

[0014] The temperature of the reaction chamber is set to 100-150° C., and then a zinc precursor source pulse of 40-80 milliseconds, a first oxygen precursor source pulse of 80-120 milliseconds, and an inert gas purge of 5-10 seconds are sequentially applied to the reaction chamber.

[0015] Optionally, in step S2, in the n-times cyclic deposition of SnO2 monolayer, each step of SnO2 monolayer deposition specifically includes:

[0016] The temperature of the reaction chamber is set to 100-150° C., and then a 40-80 millisecond tin precursor source pulse, an 80-120 millisecond second oxygen precursor source pulse, and a 5-10 second inert gas purge are sequentially applied into the reaction chamber.

[0017] Optionally, the zinc precursor source includes at least one of diethyl zinc and zinc chloride, and the first oxygen precursor source includes at least one of deionized water and ozone;

[0018] The tin precursor source includes at least one of tetrakis(dimethylamino)tin and tetraethyltin, and the second oxygen precursor source includes at least one of deionized water and ozone.

[0019] Optionally, in step S3, the number of times is 30 to 50 times.

[0020] A second aspect of the present invention provides a cadmium-free electron transport layer, wherein the cadmium-free electron transport layer is prepared by the preparation method of the present invention as described above.

[0021] The third aspect of the present invention provides an antimony-based sulfide thin-film solar cell, which includes a substrate, an antimony-based sulfide semiconductor light absorption layer, an electron transport layer and a window layer sequentially located on the substrate, and a first electrode and a second electrode respectively located on the window layer and on the substrate; the electron transport layer is the cadmium-free electron transport layer of the present invention as described above.

[0022] Optionally, the antimony-based chalcogenide semiconductor light absorption layer includes Sb2(Se x S 1-x )3, 0≤x≤1; the antimony-based chalcogenide thin film solar cell further comprises a Sb2O3 passivation layer located between the antimony-based chalcogenide semiconductor light absorption layer and the electron transport layer;

[0023] The window layer includes one of an indium tin oxide window layer, a fluorine-doped tin oxide window layer, and an aluminum-doped zinc oxide window layer;

[0024] The materials of the first electrode and the second electrode are each independently at least one of silver, aluminum, copper and nickel.

[0025] A fourth aspect of the present invention provides a method for preparing the antimony-based chalcogenide thin film solar cell as described above, comprising the following steps:

[0026] providing a substrate;

[0027] forming an antimony-based chalcogenide semiconductor light absorption layer on the substrate;

[0028] Forming a cadmium-free electron transport layer on the antimony-based chalcogenide semiconductor light absorption layer using the preparation method of the present invention as described above;

[0029] forming a window layer on the cadmium-free electron transport layer;

[0030] A first electrode and a second electrode are formed on the window layer and the substrate, respectively.

[0031] Optionally, the step of forming an antimony-based chalcogenide semiconductor light absorption layer on the substrate specifically includes:

[0032] forming a Sb precursor film on the substrate by magnetron sputtering;

[0033] Then, the Sb precursor film is subjected to selenization and / or sulfurization treatment to generate Sb2(Se xS 1-x )3, 0≤x≤1, thereby obtaining the antimony-based chalcogenide semiconductor light absorption layer.

[0034] Beneficial effects: The heterojunction energy band arrangement formed by the cadmium-free electron transport layer and the antimony-based chalcogenide semiconductor provided by the present invention presents an ideal "peak-shaped" configuration, and the corresponding conduction band order value is between 0 and 0.4 eV, which can not only effectively inhibit the aggregation and recombination of photogenerated carriers on the interface, but also ensure efficient carrier separation and transport, thereby achieving performance improvement of the corresponding device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the pulse procedure for atomic layer deposition of a cadmium-free electron transport layer in an embodiment of the present invention.

[0036] Figure 2 Schematic diagram of the atomic layer deposition process of ZnO monolayer and SnO2 monolayer in an embodiment of the present invention.

[0037] Figure 3 Schematic diagram of the structure of an antimony-based chalcogenide thin-film solar cell in an embodiment of the present invention.

[0038] Figure 4 1 is a current density-voltage curve of the antimony-based sulfur-based thin-film solar cell in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0039] The present invention provides a cadmium-free electron transport layer, an antimony-based chalcogenide thin film solar cell and a preparation method. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] The embodiment of the present invention provides a method for preparing a cadmium-free electron transport layer, wherein: Figure 1 As shown, the following steps are included:

[0042] S1, performing m cycles of ZnO monolayer deposition by atomic layer deposition to obtain a first thin film layer;

[0043] S2, performing n cycles of SnO2 monolayer deposition on the first thin film layer by atomic layer deposition to obtain a second thin film layer;

[0044] S3, repeating steps S1 to S2 several times to obtain the cadmium-free electron transport layer;

[0045] Among them, m:n=(1~6):1.

[0046] That is, the atomic layer deposition process of the present invention includes several cycles, wherein, for example Figure 1 As shown, each cycle includes m ZnO monolayer cyclic deposition (forming the first thin film layer, i.e., ZnO thin film layer) and n SnO2 monolayer cyclic deposition (forming the second thin film layer, i.e., SnO2 thin film layer). Therefore, the cadmium-free electron transport layer (which can be recorded as ZTO layer) prepared by the method includes a plurality of first thin film layers (ZnO thin film layers) and second thin film layers (SnO2 thin film layers) alternately stacked, wherein the first thin film layer includes m stacked ZnO monolayers, the second thin film layer includes n stacked SnO2 monolayers, and the ratio of m to n is (1-6):1, that is, the ratio of the number of Zn atoms to Sn atoms in the electron transport layer (i.e., ZTO layer) (i.e., the ratio of Zn elements to Sn elements in the electron transport layer) is (1-6):1. The present invention adjusts the band structure (i.e., band gap, conduction band, and valence band position) of the ZTO layer by adjusting the ratio of Zn atoms to Sn atoms. When the number ratio of Zn atoms to Sn atoms is (1 to 6):1, the heterojunction band arrangement formed by the ZTO layer and the antimony-based chalcogenide semiconductor presents an ideal "spike-shaped" configuration, and the corresponding conduction band order value is between 0 and 0.4 eV. Further, as an example, the ratio of m to n can be 1:1, 2:1, 3:1, 4:1, 5:1, or 6:1, etc.

[0047] The cadmium-free electron transport layer prepared by the atomic layer deposition technology of the present invention has high quality, suitable band gap and excellent photoelectric performance. The heterojunction energy band arrangement formed by the cadmium-free electron transport layer and the antimony-based chalcogenide semiconductor presents an ideal "spike-shaped" configuration, and the corresponding conduction band order value is between 0 and 0.4 eV, which can not only effectively inhibit the aggregation and recombination of photogenerated carriers at the interface, but also ensure efficient carrier separation and transport, thereby achieving performance improvement of the corresponding device. In step S1, in some embodiments, in the cyclic deposition of m ZnO monolayers, the steps of each ZnO monolayer deposition specifically include:

[0048] The temperature of the zinc precursor source and the first oxygen precursor source is set to room temperature, the temperature of the reaction chamber is set to 100-150°C (for example, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc.), and then a zinc precursor source pulse of 40-80 milliseconds (for example, 40 milliseconds, 50 milliseconds, 60 milliseconds, 70 milliseconds or 80 milliseconds, etc.), a first oxygen precursor source pulse of 80-120 milliseconds (for example, 80 milliseconds, 90 milliseconds, 100 milliseconds, 110 milliseconds or 120 milliseconds, etc.) and an inert gas (such as N2) purge of 5-10 seconds (for example, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds or 10 seconds, etc.) are sequentially performed.

[0049] In step S2, in some embodiments, in the n-times cyclic deposition of SnO2 monolayer, each step of SnO2 monolayer deposition specifically includes:

[0050] The temperature of the tin precursor source is set to 50-80°C (for example, 50°C, 60°C, 70°C or 80°C), the temperature of the second oxygen precursor source is set to room temperature, the temperature of the reaction chamber is set to 100-150°C (for example, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C), and then a tin precursor source pulse of 40-80 milliseconds (for example, 40 milliseconds, 50 milliseconds, 60 milliseconds, 70 milliseconds or 80 milliseconds, etc.), a second oxygen precursor source pulse of 80-120 milliseconds (for example, 80 milliseconds, 90 milliseconds, 100 milliseconds, 110 milliseconds or 120 milliseconds, etc.) and an inert gas (such as N2) purge of 5-10 seconds (for example, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds or 10 seconds, etc.) are sequentially performed.

[0051] During the above-mentioned ZnO monolayer deposition and SnO2 monolayer process, the temperature of each precursor source delivery tube (zinc precursor source delivery tube, first oxygen precursor source delivery tube, tin precursor source delivery tube and second oxygen precursor source delivery tube, when the first oxygen precursor source and the second oxygen precursor source are the same substance, the same delivery tube is used) is 80-120°C, for example, it can be 80°C, 90°C, 100°C, 110°C or 120°C, etc.

[0052] In some embodiments, the zinc precursor source includes at least one of diethylzinc (DEZ) and zinc chloride (ZnCl2), but is not limited thereto.

[0053] In some embodiments, the first oxygen precursor source includes at least one of deionized water (H2O) and ozone, but is not limited thereto.

[0054] In some embodiments, the tin precursor source includes at least one of tetrakis(dimethylamino)tin (TDMASn) and tetraethyltin, but is not limited thereto.

[0055] In some embodiments, the second oxygen precursor source includes at least one of deionized water (H2O) and ozone, but is not limited thereto.

[0056] In step S3, in some embodiments, the several times is 30 to 50 times, for example, 30 times, 35 times, 40 times, 45 times or 50 times.

[0057] The following example uses DEZ as a zinc precursor source, TDMASn as a tin precursor source, H2O as the first oxygen precursor source and the second oxygen precursor source to perform one ZnO monolayer deposition and one SnO2 monolayer deposition by atomic layer deposition to explain the deposition principle. Figure 2 As shown, a DEZ pulse is passed into the reaction chamber, and the DEZ molecules are chemically adsorbed on the substrate surface (a layer of DEZ molecules adsorbed on the substrate surface may lose one or more CH2 or other atoms), and then a H2O pulse is passed, and H2O reacts with the DEZ molecules to form a monolayer of ZnO, and then N2 is purged; then, a TDMASn pulse is passed, and the TDMASn molecules are adsorbed on the surface of the ZnO monolayer, and then a H2O pulse is passed, and H2O reacts with the TDMASn molecules to form a monolayer of SnO2.

[0058] The embodiment of the present invention further provides a cadmium-free electron transport layer, wherein the cadmium-free electron transport layer is prepared by the preparation method described above in the embodiment of the present invention. Specifically, the cadmium-free electron transport layer includes a plurality of first thin film layers and second thin film layers alternately stacked, the first thin film layer includes m stacked ZnO monolayers, and the second thin film layer includes n stacked SnO2 monolayers, wherein the ratio of m to n is (1 to 6):1.

[0059] In the embodiment of the present invention, the heterojunction energy band arrangement formed by the cadmium-free electron transport layer and the antimony-based chalcogenide semiconductor presents an ideal "peak-shaped" configuration, and the corresponding conduction band order value is between 0 and 0.4 eV, which can not only effectively inhibit the aggregation and recombination of photogenerated carriers at the interface, but also ensure efficient carrier separation and transport, thereby achieving performance improvement of the corresponding device.

[0060] In some embodiments, the number of the first film layers is the same as the number of the second film layers, that is, the number of the first film layers is 30 to 50, and the number of the second film layers is 30 to 50.

[0061] The embodiment of the present invention further provides an antimony-based chalcogenide thin film solar cell (specifically, an antimony-based chalcogenide thin film solar cell with a cadmium-free substrate structure), wherein: Figure 3As shown, the antimony-based sulfide thin film solar cell comprises a substrate 1, an antimony-based sulfide semiconductor light absorption layer 2, an electron transport layer 3 and a window layer 4 sequentially disposed on the substrate 1, and a first electrode 51 and a second electrode 52 respectively disposed on the window layer and on the substrate; the electron transport layer is a cadmium-free electron transport layer as described above in the embodiment of the present invention. That is to say, the antimony-based sulfide thin film solar cell comprises a substrate 1, an antimony-based sulfide semiconductor light absorption layer 2, an electron transport layer 3 and a window layer 4 sequentially disposed, and a first electrode 51 and a second electrode 52 respectively disposed on the window layer and on the substrate. The heterojunction energy band arrangement of the antimony-based sulfide semiconductor light absorption layer and the cadmium-free electron transport layer in the antimony-based sulfide thin film solar cell provided by the present invention presents an ideal "spike-like" configuration, and the corresponding conduction band order value is between 0-0.4 eV, which can not only effectively inhibit the accumulation and recombination of photogenerated carriers at the interface, but also ensure efficient carrier separation and transport. The cadmium-free antimony-based sulfur-based thin-film solar cell can achieve an energy conversion efficiency of 8.77%, and the open circuit voltage, short circuit current density and fill factor are 31.78 mA / cm 2 , 438mV and 63.08%.

[0062] In some embodiments, the substrate is a glass substrate with a metal (such as molybdenum) plated on the surface, but is not limited thereto.

[0063] In some embodiments, the antimony-based chalcogenide semiconductor light absorbing layer comprises Sb2(Se x S 1-x )3, 0≤x≤1. For example, the antimony-based chalcogenide semiconductor light absorption layer includes Sb2Se3, Sb2(Se 0.9 S 0.1 )3. Sb2(Se 0.8 S 0.2 )3. Sb2(Se 0.7 S 0.3 )3. Sb2(Se 0.6 S 0.4 )3. Sb2(Se 0.5 S 0.5 )3. Sb2(Se 0.4 S 0.6 )3. Sb2(Se 0.3 S 0.7 )3. Sb2(Se 0.2 S 0.8 )3. Sb2(Se 0.1 S 0.9 )3 or Sb2S3, etc.

[0064] In some embodiments, the antimony-based chalcogenide thin film solar cell further includes a Sb2O3 passivation layer between the antimony-based chalcogenide semiconductor light absorption layer and the electron transport layer. The Sb2O3 passivation layer can inhibit non-radiative recombination in the light absorption layer, thereby improving carrier lifetime, extraction efficiency, and collection efficiency.

[0065] In some embodiments, the window layer includes one of an indium tin oxide (ITO) window layer, a fluorine-doped tin oxide (FTO) window layer, and an aluminum-doped zinc oxide (AZO) window layer, but is not limited thereto.

[0066] In some embodiments, the materials of the first electrode and the second electrode are each independently at least one of silver, aluminum, copper, and nickel, but are not limited thereto.

[0067] The present invention also provides a method for preparing the antimony-based chalcogenide thin film solar cell according to the present invention, which comprises the following steps:

[0068] S11, providing a substrate;

[0069] S12, forming an antimony-based chalcogenide semiconductor light absorption layer on the substrate;

[0070] S13, forming a cadmium-free electron transport layer on the antimony-based chalcogenide semiconductor light absorption layer using the preparation method described above in the embodiment of the present invention;

[0071] S14, forming a window layer on the cadmium-free electron transport layer;

[0072] S15, forming a first electrode and a second electrode on the window layer and the substrate respectively.

[0073] The present invention grows a high-quality cadmium-free electron transport layer with a suitable band gap and excellent photoelectric performance on the antimony-based chalcogenide semiconductor light absorption layer, while systematically optimizing the heterojunction interface band matching and carrier dynamics, and ultimately achieves an overall improvement in the key performance of the device through coordinated regulation.

[0074] In step S11, the selection of the substrate is as described above and will not be repeated here.

[0075] In step S12, in some embodiments, the step of forming an antimony-based chalcogenide semiconductor light absorption layer on the substrate specifically includes:

[0076] S121, forming a Sb precursor thin film on the substrate by using a radio frequency magnetron sputtering method;

[0077] S122, then the Sb precursor film is subjected to selenization and / or sulfurization treatment to generate Sb2(Se x S 1-x)3, 0≤x≤1, thereby obtaining the antimony-based chalcogenide semiconductor light absorption layer.

[0078] The present invention prepares an antimony-based chalcogenide semiconductor light absorption layer by combining radio frequency magnetron sputtering with selenization and / or sulfidation processes.

[0079] In some implementations, step S121 specifically includes:

[0080] Using Sb as a target material, at a power of 10 to 50 W (for example, 10 W, 20 W, 30 W, 40 W or 50 W, etc.) and a working pressure of 0.5 to 2 Pa (for example, 0.5 Pa, 1 Pa, 1.5 Pa or 2 Pa, etc.), radio frequency magnetron sputtering deposition is performed on the substrate for 25 to 50 min (for example, 25 min, 30 min, 35 min, 40 min, 45 min or 50 min, etc.) to obtain a Sb precursor film;

[0081] In some implementations, step S122 specifically includes:

[0082] The substrate with the Sb precursor film on the surface, Se particles and / or S powder are placed in a quartz tube, and selenized and / or sulfurized for 20 to 40 minutes (for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes) at a temperature of 400 to 500°C (for example, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C) to generate Sb2(Se x S 1-x )3.

[0083] In some specific implementations, step S122 specifically includes the following steps:

[0084] A substrate with a Sb precursor film on its surface is placed in the middle temperature zone of a three-zone vacuum quartz tube, Se particles and S powder are placed in the left and right temperature zones of the three-zone vacuum quartz tube respectively (or Se particles are placed in the right temperature zone of the three-zone vacuum quartz tube, and no substance is placed in the right temperature zone; or S powder is placed in the right temperature zone of the three-zone vacuum quartz tube, and no substance is placed in the left temperature zone), an inert gas (such as argon to remove residual impurity gas) is introduced, the temperature of the three-zone vacuum quartz tube is set to 400-500°C, the processing time is 20-40min (i.e., the processing time is 20-40min at a temperature of 400-500°C), and the working pressure in the three-zone vacuum quartz tube is maintained at 0.5-3mTorr (for example, 0.5mTorr, 1mTorr, 1.5mTorr, 2mTorr, 2.5mTorr or 3mTorr, etc.), to generate Sb2(Se x S1-x )3.

[0085] In step S13, due to the presence of suitable temperature and oxygen source during the atomic layer deposition process, and the presence of Sb dangling bonds on the surface of the antimony-based chalcogenide semiconductor light absorption layer, when a cadmium-free electron transport layer is formed on the antimony-based chalcogenide semiconductor light absorption layer using the preparation method described above in the embodiment of the present invention, an ultra-thin Sb2O3 passivation layer is formed on the surface of the antimony-based chalcogenide semiconductor light absorption layer (the Sb dangling bonds on the surface of the antimony-based chalcogenide semiconductor light absorption layer react with the oxygen source diffused to the surface of the antimony-based chalcogenide semiconductor light absorption layer to form Sb2O3. In the present invention, the increase in oxygen vacancy concentration found by X-ray photoelectron spectroscopy indirectly proves the formation of the Sb2O3 passivation layer). The passivation Sb2O3 layer can inhibit non-radiative recombination in the light absorption layer and improve the carrier lifetime, extraction efficiency and collection efficiency.

[0086] In step S14, the present invention does not limit the preparation method of the window layer. Exemplarily, magnetron sputtering can be selected for preparation.

[0087] In step S15, the present invention does not limit the preparation method of the first electrode and the second electrode. Exemplarily, the first electrode and the second electrode can be prepared by thermal evaporation.

[0088] The present invention will be further described below by means of specific examples.

[0089] Example 1

[0090] This embodiment provides a method for preparing an antimony-based chalcogenide thin film solar cell, comprising the following steps:

[0091] Radio frequency magnetron sputtering (magnetron sputtering equipment purchased from Shenyang Pengcheng Vacuum Technology Co., Ltd., model TCDP-Ⅱ) was used, Sb was used as the target, and it was deposited on a molybdenum-coated glass substrate for 25 minutes at a power of 30 W and a working pressure of 1.0 Pa to form a Sb precursor film (the side of the glass substrate containing molybdenum was bonded to the Sb precursor film);

[0092] The molybdenum-coated glass substrate with Sb precursor film on the surface was placed in the middle temperature zone of the three-zone vacuum quartz tube, and two quartz boats containing Se particles (0.2g) and S powder (0.05g) were placed in the left and right temperature zones respectively. High-purity argon gas was introduced into the tube to remove the residual impurity gas, and the gas pressure in the quartz tube was maintained at 30KPa. Then, the substrate was gradually heated to 415℃ at a heating rate of 20℃ per minute, and sulfurization and selenization treatment were performed at 415℃ for 35min, so that Se and S reacted with the Sb precursor to generate Sb2(Se x S 1-x)3, x=0.8, the working pressure is maintained at 2.5mTorr; after cooling, an antimony-based chalcogenide semiconductor light absorption layer with a thickness of 220nm is obtained.

[0093] The ZTO layer with a Zn to Sn atomic ratio of 4:1, i.e., a cadmium-free electron transport layer, was deposited on the antimony-based chalcogenide semiconductor light absorption layer by an atomic layer deposition process (atomic layer deposition equipment purchased from Dongguan Nafeng Microelectronics Equipment Co., Ltd., model NCE-200R). In this process, diethylzinc (DEZ), tetrakis(dimethylamino)tin (TDMASn) and H2O were used as zinc precursor sources, tin precursor sources, and oxygen precursor sources, respectively. The temperatures of DEZ and H2O were kept at room temperature, while the temperature of the stainless steel container storing TDMASn was set to 65°C, and the temperatures of the delivery pipe (delivery pipes of each precursor source) and the reaction chamber were set to 100°C and 120°C, respectively. The atomic layer deposition program included 50 cycles, each of which included 4 ZnO monolayer deposition cycles and 1 SnO2 monolayer deposition. The process parameters for each ZnO monolayer deposition were: 50 milliseconds of DEZ pulse, 80 milliseconds of H2O pulse, and 5 seconds of N2 purge; the process parameters for one SnO2 monolayer deposition were: 50 milliseconds of TDMASn pulse, 80 milliseconds of H2O pulse, and 5 seconds of N2 purge. After 50 cycles, a cadmium-free electron transport layer was formed.

[0094] Under the conditions of pressure and power of 0.35 Pa and 120 W respectively, magnetron sputtering deposition is performed on the cadmium-free electron transport layer to form an ITO window layer with a thickness of 400 nm.

[0095] A first electrode (silver electrode) and a second electrode (silver electrode) with a thickness of 80 nm are formed on an ITO window layer and a molybdenum-plated glass substrate respectively by thermal evaporation to obtain the antimony-based sulfur-based thin-film solar cell.

[0096] Comparative Example 1

[0097] This embodiment provides an antimony-based sulfide thin film solar cell, which is different from the embodiment 1 only in that a CdS electron transport layer is used to replace the cadmium-free electron transport layer. The current density-voltage curves of the antimony-based sulfide thin film solar cells in the embodiment 1 and the comparative example 1 are shown in FIG. Figure 4 As shown in Figure 1, it can be seen that the antimony-based sulfur-based thin-film solar cell in Example 1 can achieve an energy conversion efficiency of 8.77%, and the open circuit voltage, short circuit current density and fill factor are 31.78 mA / cm 2 , 438mV and 63.08%, which is the highest efficiency value reported so far for cadmium-free antimony-based sulfur-based thin-film solar cells. The energy conversion efficiency of the antimony-based sulfur-based thin-film solar cell in Comparative Example 1 is only 5.85%, and the open circuit voltage, short circuit current density and fill factor are 25.68mA / cm2 , 428mV and 53.23%.

[0098] In summary, the present invention provides a cadmium-free electron transport layer, an antimony-based sulfide thin film solar cell and a preparation method. The heterojunction energy band arrangement formed by the cadmium-free electron transport layer and the antimony-based sulfide semiconductor provided by the present invention presents an ideal "spike-shaped" configuration, and the corresponding conduction band order value is between 0 and 0.4 eV, which can not only effectively inhibit the aggregation and recombination of photogenerated carriers on the interface, but also ensure efficient carrier separation and transport. The cadmium-free antimony-based sulfide thin film solar cell can achieve an energy conversion efficiency of 8.77%, and the open circuit voltage, short circuit current density and fill factor can reach 31.78 mA / cm 2 , 438mV and 63.08%.

[0099] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a cadmium-free electron transport layer, characterized in that: The steps include: S1, performing m cycles of ZnO monolayer deposition by atomic layer deposition to obtain a first thin film layer; S2, performing n cycles of SnO2 monolayer deposition on the first thin film layer by atomic layer deposition to obtain a second thin film layer; S3, repeating steps S1 to S2 several times to obtain the cadmium-free electron transport layer; Among them, m:n=(1~6):

1.

2. The preparation method according to claim 1, characterized in that: In step S1, in the m-times cyclic deposition of ZnO monolayer, the steps of each ZnO monolayer deposition specifically include: The temperature of the reaction chamber is set to 100-150° C., and then a zinc precursor source pulse of 40-80 milliseconds, a first oxygen precursor source pulse of 80-120 milliseconds, and an inert gas purge of 5-10 seconds are sequentially applied to the reaction chamber.

3. The preparation method according to claim 2, characterized in that: In step S2, in the n-times cyclic deposition of SnO2 monolayer, each step of SnO2 monolayer deposition specifically includes: The temperature of the reaction chamber is set to 100-150° C., and then a 40-80 millisecond tin precursor source pulse, an 80-120 millisecond second oxygen precursor source pulse, and a 5-10 second inert gas purge are sequentially applied into the reaction chamber.

4. The preparation method according to claim 3, characterized in that: The zinc precursor source includes at least one of diethyl zinc and zinc chloride, and the first oxygen precursor source includes at least one of deionized water and ozone; The tin precursor source includes at least one of tetrakis(dimethylamino)tin and tetraethyltin, and the second oxygen precursor source includes at least one of deionized water and ozone.

5. The preparation method according to claim 1, characterized in that: In step S3, the several times is 30 to 50 times.

6. A cadmium-free electron transport layer, characterized in that: The cadmium-free electron transport layer is prepared by the preparation method according to any one of claims 1 to 5.

7. An antimony-based chalcogenide thin film solar cell, characterized in that: It comprises a substrate, an antimony-based chalcogenide semiconductor light absorption layer, an electron transport layer and a window layer sequentially located on the substrate, and a first electrode and a second electrode respectively located on the window layer and on the substrate; the electron transport layer is the cadmium-free electron transport layer as claimed in claim 6.

8. The antimony-based chalcogenide thin film solar cell according to claim 7, characterized in that: The antimony-based chalcogenide semiconductor light absorption layer includes Sb2(Se x S 1-x )3, 0≤x≤1; the antimony-based chalcogenide thin film solar cell further comprises a Sb2O3 passivation layer located between the antimony-based chalcogenide semiconductor light absorption layer and the electron transport layer; The window layer includes one of an indium tin oxide window layer, a fluorine-doped tin oxide window layer, and an aluminum-doped zinc oxide window layer; The materials of the first electrode and the second electrode are each independently at least one of silver, aluminum, copper and nickel.

9. A method for preparing an antimony-based chalcogenide thin film solar cell according to claim 7, characterized in that: The steps include: providing a substrate; forming an antimony-based chalcogenide semiconductor light absorption layer on the substrate; Forming a cadmium-free electron transport layer on the antimony-based chalcogenide semiconductor light absorption layer using the preparation method described in any one of claims 1 to 5; forming a window layer on the cadmium-free electron transport layer; A first electrode and a second electrode are formed on the window layer and the substrate, respectively.

10. The preparation method according to claim 9, characterized in that: The step of forming an antimony-based chalcogenide semiconductor light absorption layer on the substrate specifically comprises: forming a Sb precursor film on the substrate by magnetron sputtering; Then, the Sb precursor film is subjected to selenization and / or sulfurization treatment to generate Sb2(Se x S 1-x )3, 0≤x≤1, thereby obtaining the antimony-based chalcogenide semiconductor light absorption layer.

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