Green, cadmium-free, efficient and stable electron transport layer, preparation method and application thereof

Abstract

The invention relates to the field of semiconductor film photoelectric devices, in particular to a green, cadmium-free, efficient and stable electron transport layer, a preparation method and application thereof. The green, cadmium-free, efficient and stable electron transport layer comprises a ternary compound (Zn, Ti) O. The preparation method of the green, cadmium-free, efficient and stable electron transport layer comprises the following steps that a clean substrate is taken, and a ZnO deposition procedure and a TiO2 deposition procedure are sequentially and alternately carried out on the substrate for a plurality of times. The invention innovatively designs a green, cadmium-free, efficient and stable electron transport layer (comprising a ternary compound (Zn, Ti) O). The energy band structure of the electron transport layer can be continuously adjusted through the Zn / Ti proportion; the carrier mobility can be effectively improved through modification of Ti ions on a ZnO conduction band; the intrinsic thermodynamic stability of TiO2 can ensure the long-time working stability of the photoelectrode based on the green, cadmium-free, efficient and stable electron transport layer in electrolyte.

Description

Technical Field

[0001] This invention relates to the field of semiconductor thin-film optoelectronic devices, and in particular to a green, cadmium-free, highly efficient and stable electron transport layer, its preparation method, and its application. Background Technology

[0002] Hydrogen energy boasts numerous advantages, including being environmentally friendly, having high energy conversion efficiency, and high calorific value, making it a crucial vehicle for achieving a green and low-carbon transformation. Photoelectrochemical water splitting, based on photoelectrochemical reactions, is an important means of converting solar energy into green hydrogen energy. Representative photoelectrochemical (PEC) water splitting systems can drive the decomposition reaction at low overpotentials using photogenerated electrons and holes, producing hydrogen and oxygen at the corresponding photoelectrode. As a key component, an ideal photoelectrode needs to efficiently perform tasks such as light absorption, charge separation / transfer, and inducing interfacial redox reactions. Recent studies have shown that photovoltaic-based photoelectrodes can positively utilize the photovoltaic effect to enhance charge separation and transport. Representative chalcogenide thin-film photoelectrodes, such as Cu(In,Ga)Se2, Cu2ZnSnS4, and Sb2Se3, which retain the core photovoltaic structure, have reported very impressive solar photoelectric water splitting hydrogen production efficiencies.

[0003] Carrier recombination at the photoelectrode interface of chalcogenide thin films is a crucial factor affecting device efficiency. Specifically, carrier recombination at the interface of the light-absorbing layer / electron transport layer in chalcogenide semiconductors significantly impacts charge separation efficiency. For PN heterojunctions with photovoltaic-like structures, selecting a suitable N-type electron transport layer to match the P-type chalcogenide light-absorbing layer can yield ideal built-in potential and depletion layer width, thereby improving charge separation efficiency and device energy conversion efficiency.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a green, cadmium-free, efficient and stable electron transport layer, its preparation method and its application, aiming to solve the problem that carrier recombination at the interface of the existing chalcogenide semiconductor light absorption layer / electron transport layer significantly affects the charge separation efficiency.

[0006] The first aspect of this invention provides a method for preparing a green, cadmium-free, highly efficient, and stable electron transport layer, which employs atomic layer deposition to prepare the green, cadmium-free, highly efficient, and stable electron transport layer, specifically including the following steps: Take a clean substrate and perform ZnO deposition and TiO2 deposition processes alternately several times on the substrate.

[0007] Optionally, each ZnO deposition process includes several ZnO pulse processes, and the thickness of ZnO deposited in each ZnO pulse process is 0.1 ± 10% nm.

[0008] Optionally, a single TiO2 deposition process includes several TiO2 pulse processes, with each TiO2 pulse process depositing a TiO2 thickness of 0.07 ± 10% nm.

[0009] Optionally, the ratio of the number of ZnO pulses in each ZnO deposition process to the number of TiO2 pulses in each TiO2 deposition process is 1-9:1.

[0010] Optionally, the ZnO pulse program includes a zinc source pulse of 40-80 milliseconds, an oxygen source pulse of 80-120 milliseconds, and an N2 purge of 5-10 seconds; And / or, the TiO2 pulse program includes a 40-80 ms titanium source pulse, an 80-120 ms oxygen source pulse, and a 5-10 sec N2 purge.

[0011] Optionally, a 15-25 second N2 purging procedure is included between each ZnO deposition procedure and TiO2 deposition procedure.

[0012] Optionally, the zinc source is diethylzinc (DEZ), dimethylzinc, or a zinc amide compound, preferably diethylzinc; the titanium source is titanium tetrachloride (TiCl4), a chloride of titanium alkoxide, or trimethyl (cyclopentadienyl) titanium, preferably titanium tetrachloride; and the oxygen source is deionized water or ozone, preferably deionized water.

[0013] Optionally, the temperature of the conveying pipes for conveying the zinc source, titanium source, and oxygen source is 80-120°C.

[0014] Optionally, the deposition temperature is 150-190℃.

[0015] A second aspect of the present invention provides a green, cadmium-free, highly efficient and stable electron transport layer, prepared by the method described above, or comprising a ternary compound (Zn, Ti)O.

[0016] The third aspect of the present invention provides the application of a green, cadmium-free, highly efficient and stable electron transport layer in a photoelectrode for photoelectric water splitting to produce hydrogen.

[0017] The fourth aspect of the present invention provides a photoelectrode for photocatalytic water splitting to produce hydrogen, comprising a heterojunction composed of the aforementioned green, cadmium-free, highly efficient and stable electron transport layer and light absorption layer.

[0018] Optionally, the thickness of the electron transport layer is 15-30 nm.

[0019] Optionally, the light-absorbing layer is an Sb2Se3 light-absorbing layer with a thickness of 1000-1500 nm.

[0020] The fifth aspect of the present invention provides a method for preparing a photoelectrode for photocatalytic water splitting to produce hydrogen, comprising the following steps: preparing an electron transport layer on the Sb2Se3 light absorption layer, and then treating it under vacuum conditions at 250-350°C for 30-50 minutes.

[0021] Beneficial effects: This invention innovatively designs a green, cadmium-free, highly efficient, and stable electron transport layer (comprising a ternary compound (Zn, Ti)O). Its band structure can be continuously adjusted by the Zn / Ti ratio; the modification of the ZnO conduction band by Ti ions can effectively improve carrier mobility; the intrinsic thermodynamic stability of TiO2 ensures the long-term working stability of the photoelectrode based on this green, cadmium-free, highly efficient, and stable electron transport layer in the electrolyte. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the pulse program for the atomic layer deposition method in Example 1.

[0023] Figure 2 This represents the band matching between (Zn,Ti)O and Sb2Se3.

[0024] Figure 3 The image shows the current-voltage test (top left) and the calculated half-cell solar-hydrogen energy conversion efficiency (bottom right) of the device in Example 1.

[0025] Figure 4 The image shows the current-time stability test results of the device in Example 1.

[0026] Figure 5 The diagram shows the current-voltage test results (top left) and the calculated half-cell solar-hydrogen energy conversion efficiency (bottom right) for the device in Comparative Example 1.

[0027] Figure 6 The current-time stability test results are shown for the device in Comparative Example 1. Detailed Implementation

[0028] This invention provides a green, cadmium-free, highly efficient, and stable electron transport layer, its preparation method, and its applications. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Taking Sb₂Se₃ photoelectrodes as an example, TiO₂ was initially chosen as the N-type electron transport layer (ETL). The conduction band matching of Sb₂Se₃ / TiO₂ coincided with the water reduction potential, and the ideal band bending also facilitated charge separation. However, its high band gap resulted in a large mismatch in the valence band. To address this, researchers inserted a CdS buffer layer between Sb₂Se₃ and TiO₂ to construct an ideal conduction band offset (CBO) at the PN junction interface, enhancing charge separation. Subsequently, studies have employed CdS / TiO₂ / SnO₂ stacks and CdS / TiO₂ photoelectrodes with tunable band structures. m Zn 1-m CdS-doped CdS(In) is used as an ETL (electrode transfer layer) to improve photoelectrode performance by optimizing its band alignment with Sb₂Se₃. However, CdS-based ETLs suffer from intrinsic biotoxicity, parasitic current loss due to the absorption of some high-energy photons (400-600 nm), and the effects of thermal / optical treatment on CdS. 2+ and S 2- The performance degradation caused by ion diffusion is also a significant concern. Therefore, some representative green cadmium-free ETLs, such as ZnO, SnO2, and (Zn,Sn)O, have gradually attracted attention and achieved some research progress. However, the corresponding device performance (taking the Sb2Se3 / (Zn,Sn)O photoelectrode as an example, its highest half-cell solar-to-hydrogen conversion efficiency is 4.32%, and its photocurrent density is 31.8 mA / cm²) remains to be seen. -2 The initial potential is 0.45V. RHE The performance of the photoelectrode of the same type, Sb₂Se₃ / CdS(In), is as follows: half-cell solar-to-hydrogen conversion efficiency is 5.6%, and photocurrent density is 35.7 mA / cm². -2 The initial potential is 0.54V. RHE Compared to [previous technologies], there is still a significant gap. Furthermore, the long-term operational stability of green, cadmium-free devices also faces challenges.

[0030] Therefore, it is crucial to design novel tunable band structure electron transport layers, regulate the interface performance of PN heterojunctions, improve charge separation efficiency, and realize the construction and application of truly green, cadmium-free, efficient and stable photovoltaic-like thin-film photoelectrodes for water splitting to produce hydrogen.

[0031] Based on this, this embodiment provides a method for preparing a green, cadmium-free, highly efficient, and stable electron transport layer. The method employs atomic layer deposition to prepare the green, cadmium-free, highly efficient, and stable electron transport layer, specifically including the following steps: Take a clean substrate and perform ZnO deposition and TiO2 deposition processes alternately several times on the substrate.

[0032] This embodiment uses alternating deposition, which not only ensures that the Zn source does not react with the Ti source to generate other byproducts, but also ensures that ZnO and TiO2 are alternately stacked and interpenetrated to generate a new material (Zn,Ti)O that is mutually incorporated. Otherwise, if ZnO is deposited first and then TiO2 is deposited, there will be two separate layers.

[0033] In some implementations, each ZnO deposition process includes several ZnO pulse processes, and the thickness of ZnO deposited by each ZnO pulse process is 0.1 ± 10% nm.

[0034] In some implementations, a single TiO2 deposition process includes several TiO2 pulse processes, each of which deposits a TiO2 thickness of 0.07 ± 10% nm.

[0035] In some implementations, the ratio of the number of ZnO pulses in each ZnO deposition process to the number of TiO2 pulses in each TiO2 deposition process is 1-9:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1.

[0036] It should be noted that the number of cycles and the thickness control are based on the thickness of ZnO and TiO2 deposited in each cycle. For example, if a total thickness of 15 nm (Zn, Ti)O is required, and the Zn:Ti ratio is 4:1, a single cycle consists of 4 ZnO and 1 TiO2 deposition, with a single deposition thickness of 0.1*4 + 0.07 = 0.47 nm. The total number of cycles is approximately 15 / 0.47 ≈ 32. If a total thickness of 30 nm (Zn, Ti)O is required, approximately 64 total cycles are needed. Therefore, alternating cycles between 32 and 64 are possible.

[0037] like Figure 1 As shown, the ZnO pulse program in this embodiment includes a zinc source pulse of 40-80 milliseconds, an oxygen source pulse of 80-120 milliseconds, and an N2 purge of 5-10 seconds (e.g., 5s). The TiO2 pulse program includes a 40-80 ms titanium source pulse, an 80-120 ms oxygen source pulse, and a 5-10 second (e.g., 5 s) N2 purging.

[0038] Each ZnO deposition procedure and TiO2 deposition procedure includes a 15-25 second N2 purging procedure.

[0039] In this embodiment, the zinc source pulse is immediately followed by the oxygen source pulse. The two pulsed gases react within the reaction chamber, and after a layer of ZnO is formed, excess gas is purged with N2 before the next reaction. This ensures that the products of the next reaction are not affected, guaranteeing that each reaction is independent. The same applies to the titanium source. Since the zinc and titanium sources react with each other, to prevent the Zn and Ti sources from reacting and generating other byproducts, a slightly longer N2 purging time is used to ensure that no residual gas remains in the reaction chamber. The short purging time described above, because it involves the same reactant, has minimal impact due to slight residual gas.

[0040] It should be noted that in this embodiment, the zinc source pulse reacts with the oxygen source pulse to generate a layer of ZnO. In this cycle, x zinc source pulses and x oxygen source pulses are used respectively to generate x layers of ZnO. Similarly, the titanium source pulse reacts with the oxygen source pulse to generate a layer of TiO2. In this cycle, y titanium source pulses and y oxygen source pulses are used respectively to generate y layers of TiO2.

[0041] In some embodiments, the zinc source is diethylzinc (DEZ), dimethylzinc, or a zinc amide compound, preferably diethylzinc; the titanium source is titanium tetrachloride (TiCl4), a chloride of titanium alkoxide, or trimethyl (cyclopentadienyl) titanium, preferably titanium tetrachloride; and the oxygen source is deionized water or ozone, preferably deionized water.

[0042] In some implementations, the temperature of the delivery pipes for conveying the zinc source, titanium source, and oxygen source is 80-120°C.

[0043] In some implementations, the deposition temperature is 150-190°C.

[0044] It should be noted that the source bottle temperature < delivery pipe temperature < reaction chamber temperature to ensure that the gas flows from the low temperature to the high temperature. The deposition temperature is determined by the temperature required for the reaction; this value is the result of trials to confirm that the reaction can proceed.

[0045] This embodiment also provides a green, cadmium-free, highly efficient, and stable electron transport layer, comprising a ternary compound (Zn,Ti)O. The ternary compound (Zn,Ti)O of this embodiment is composed of Zn, Ti, and O, wherein the atomic ratio of Zn to Ti is 1-9:1, and can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1.

[0046] This embodiment presents a green, cadmium-free, highly efficient, and stable electron transport layer (comprising a ternary compound (Zn, Ti)O). In terms of theoretical material analysis, firstly, its band structure can be continuously adjusted through the Zn / Ti ratio; secondly, the modification of the ZnO conduction band by Ti ions can effectively improve carrier mobility; and finally, the intrinsic thermodynamic stability of TiO2 ensures the long-term operational stability of the photoelectrode based on this green, cadmium-free, highly efficient, and stable electron transport layer in the electrolyte. This embodiment does not contain cadmium, thus solving the problems of biotoxicity and photocorrosion.

[0047] This embodiment also provides an application of a green, cadmium-free, highly efficient, and stable electron transport layer in the photoelectrode for photoelectric water splitting to produce hydrogen.

[0048] This embodiment also provides a photoelectrode for hydrogen production by photocatalytic water splitting, comprising a heterojunction composed of the aforementioned green, cadmium-free, highly efficient and stable electron transport layer and light absorption layer.

[0049] In some embodiments, the thickness of the electron transport layer is 15-30 nm, such as 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, or 30 nm.

[0050] In some embodiments, the light-absorbing layer is an Sb2Se3 light-absorbing layer with a thickness of 1000-1500nm, such as 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, or 1500nm.

[0051] This embodiment also provides a method for preparing a photoelectrode for hydrogen production by photocatalytic water splitting, comprising the following steps: preparing an electron transport layer on the Sb2Se3 light absorption layer, and then treating it under vacuum conditions at 250-350°C for 30-50 minutes.

[0052] It should be noted that the above heat treatment can strengthen the built-in electric field and passivate interface defects.

[0053] Example 1 1. A method for preparing a green, cadmium-free, highly efficient, and stable electron transport layer, comprising the following steps: A clean substrate was taken, and ZnO deposition and TiO2 deposition processes were performed alternately 53 times on the substrate.

[0054] Each ZnO deposition process includes four ZnO pulse processes, with each ZnO pulse process depositing a ZnO thickness of 0.1 nm; each TiO2 deposition process includes one TiO2 pulse process, with each TiO2 pulse process depositing a TiO2 thickness of 0.07 nm.

[0055] In this embodiment, the ZnO pulse program includes an 80-millisecond zinc source pulse, a 120-millisecond oxygen source pulse, and a 5-second N2 purge pulse; the TiO2 pulse program includes an 80-millisecond titanium source pulse, a 120-millisecond oxygen source pulse, and a 5-second N2 purge pulse; a 15-second N2 purge is included between each ZnO deposition program and the TiO2 deposition program; the zinc source is diethylzinc, the titanium source is titanium tetrachloride, and the oxygen source is deionized water. The temperature of the delivery pipes for the zinc, titanium, and oxygen sources is 100°C; the deposition temperature is 190°C.

[0056] The thickness of the green, cadmium-free, highly efficient and stable electron transport layer obtained in this embodiment is 25 nm.

[0057] The green, cadmium-free, highly efficient, and stable electron transport layer obtained in this embodiment is a ternary compound (Zn,Ti)O.

[0058] 2. Heterojunction: In this embodiment, the substrate is a 1000nm thick Sb2Se3 light-absorbing layer.

[0059] 3. A photoelectrode for hydrogen production by photocatalytic water splitting, wherein the photoelectrode structure in this embodiment is Mo / Sb2Se3 / (Zn,Ti)O / Pt.

[0060] Sb₂Se₃: Based on a Mo-coated glass substrate, a precursor Sb thin film was magnetron sputtered at a sputtering power of 30 W, a sputtering pressure of 1.5 Pa, and a sputtering time of 40 min, resulting in an Sb thickness of approximately 600 nm. Following selenization, a 1 μm thick Sb₂Se thin film was grown through a chemical reaction. Selenization was performed at 400 °C for 15 min, producing a micron-sized, tightly packed Sb₂Se thin film with a preferred [hk₁] orientation and stoichiometric elemental composition.

[0061] Pt: A Pt cocatalyst was deposited for 50 seconds at a current of 20 mA using an automated sputtering machine. Finally, an Ag colloidal coating was applied to the exposed Mo layer at the film edge and allowed to cure on the surface to provide a conductive back contact.

[0062] like Figure 2 As shown, the heterojunction obtained in this embodiment has an ideal spike-like band matching, which can enhance charge separation efficiency.

[0063] Peak-type band matching is a structure where the conduction band bottom of one semiconductor material and the valence band top of another material form a structure resembling a "peak" and a "valence valley" at the interface. Specifically, for a heterojunction composed of semiconductors A and B: the conduction band bottom (E0) of semiconductor A... C-A The conduction band bottom (E) of semiconductor B is higher than that of semiconductor B. C-B On the band diagram, at the interface, the conduction band of A bends downward to form a downward "peak", while the conduction band of B bends upward to form a "valley".

[0064] The biggest advantage of peak-type band matching is that it efficiently separates photogenerated carriers (electrons and holes) and suppresses their recombination.

[0065] 1. Highly efficient charge separation: When light irradiates and generates electron-hole pairs, due to the alternating band structure, photogenerated electrons naturally flow from the higher A-conduction band to the lower B-conduction band. Simultaneously, photogenerated holes flow from the lower B-valence band to the higher A-valence band. This process spatially separates electrons and holes into two different materials.

[0066] 2. Suppress carrier recombination: Because electrons and holes are physically isolated on opposite sides of the interface, the probability of them meeting and recombinating is greatly reduced. More importantly, the "peak" itself forms an energy barrier. For electrons that have migrated to material B, in order to cross this "peak" back to material A and recombine with the holes there, they need to overcome this energy barrier (ΔE). C This is kinetically unfavorable, thus further inhibiting recombination.

[0067] 3. Improve carrier lifetime and utilization: Recombination suppression means that photogenerated carriers have a longer lifetime, allowing more time to be collected by the electrodes or participate in surface chemical reactions (such as photocatalytic water splitting and CO2 reduction), thereby significantly improving the photoelectric conversion efficiency or quantum efficiency of the device.

[0068] The counterpart to peak-type band matching is cliff-type band matching. The key difference between it and peak-type band matching lies in the conduction band offset ΔE. C Symbol: In cliff-type, the conduction band bottom (E) of semiconductor A C-A Below the conduction band bottom (E) of semiconductor B C-B (i.e., ΔE) C <0). This makes the energy band continuously decrease as electrons flow from A to B, like a "cliff", with no reverse potential barrier.

[0069] Cliff-shaped structures are generally detrimental and should be avoided as much as possible in device design: 1. Interfacial recombination centers: While this smooth descent facilitates electron transport from A to B, it also greatly favors electrons flowing back from B to A. Defects at the interface become recombination centers, causing electrons flowing back from B to A to recombine violently with holes in A.

[0070] 2. High recombination rate: Due to the lack of a barrier like the spike type, carrier recombination is very serious, which leads to a sharp drop in device efficiency.

[0071] 3. Reduced Open-Circuit Voltage (Voc): In solar cells, cliff-type alignment is a significant cause of open-circuit voltage loss. In the field of photoelectrochemical water splitting, this manifests as a decrease in initial potential.

[0072] The Mo / Sb₂Se₃ / (Zn,Ti)O / Pt thin-film photoelectrode of this embodiment exhibited an efficiency of 31.1 mA / cm² under standard sunlight AM1.5G irradiation in an H₂SO₄ electrolyte at pH=1. -2 The photocurrent density is 0.53V. RHE At the initial potential, the half-cell solar-to-hydrogen conversion efficiency is as high as 5.27%, such as Figure 3 As shown. Performance degradation is less than 5% after 4-6 hours of operation, such as... Figure 4 As shown in the figure, this performance is comparable to the best efficiency of similar Sb₂Se₃ / CdS photoelectrodes, and represents the highest energy conversion efficiency of current green cadmium-free Sb₂Se₃ photoelectrodes. Long-term testing of its IT curve showed that after 5 hours, the generated photocurrent differed from the initial value by no more than 5%, indicating its excellent stability.

[0073] It should be noted that photocurrent density reflects the current intensity of the electrode driving the hydrogen evolution reaction under illumination, and is directly related to the hydrogen production. A higher photocurrent density indicates that the device has a strong ability to generate and transfer photogenerated carriers, and is a core indicator for evaluating the hydrogen production capacity of the photoelectrode. The results of this study are close to the advanced level of photoelectrochemical systems. The device operates at 0.53V... RHE This indicates a significant photocurrent, signifying the initiation of the hydrogen evolution reaction. For the photocathode, a more positive initial potential value indicates that the device can drive the reaction at a lower applied energy, demonstrating a higher photogenerated voltage and excellent bandgap matching performance. The 0.53V obtained in this embodiment... RHE The initial potential is at a relatively high level compared to similar materials. This embodiment achieves a half-cell solar-to-hydrogen conversion efficiency of 5.27%, indicating that approximately 5% of the incident solar energy is directly converted into chemical energy stored in hydrogen. This value comprehensively reflects the device's light absorption efficiency, carrier utilization efficiency, and interfacial reaction kinetics performance, and is an important indicator for evaluating the overall performance of the photoelectrode.

[0074] Comparative Example 1 The difference between this comparative example and Example 1 is that the preparation method of the electron transport layer in this comparative example specifically includes the following steps: Take a clean substrate and perform 23 alternating ZnO deposition and TiO2 deposition processes on the substrate.

[0075] Each ZnO deposition process consists of 10 ZnO pulse cycles, with each ZnO pulse cycle depositing a ZnO thickness of 0.1 nm; each TiO2 deposition process consists of 1 TiO2 pulse cycle, with each TiO2 pulse cycle depositing a TiO2 thickness of 0.07 nm.

[0076] The comparative example ZnO pulse program included an 80 ms zinc source pulse, a 120 ms oxygen source pulse, and a 5-second N2 purge pulse; the TiO2 pulse program included an 80 ms titanium source pulse, a 120 ms oxygen source pulse, and a 5-second N2 purge pulse; a 15-second N2 purge was included between each ZnO deposition program and the TiO2 deposition program; the zinc source was diethylzinc, the titanium source was titanium tetrachloride, and the oxygen source was deionized water. The temperature of the delivery tubes for the zinc, titanium, and oxygen sources was 100°C; the deposition temperature was 190°C.

[0077] The thickness of the green, cadmium-free, highly efficient, and stable electron transport layer obtained in this comparative example is 25 nm.

[0078] The Mo / Sb₂Se₃ / (Zn,Ti)O / Pt thin-film photoelectrode of this comparative example, under standard sunlight AM 1.5G irradiation in an H₂SO₄ electrolyte at pH=1, exhibited a wavelength of 17.2 mA / cm². -2 Photocurrent density, 0.35V RHE At the initial potential, the half-cell solar-to-hydrogen conversion efficiency is only 1.03%, such as Figure 5 As shown. From Figure 6 It can be seen that the test current has already decreased significantly after 1 hour.

[0079] In summary, this invention provides a green, cadmium-free, highly efficient, and stable electron transport layer (comprising a ternary compound (Zn, Ti)O). Its band structure can be continuously adjusted by the Zn / Ti ratio; the modification of the ZnO conduction band by Ti ions can effectively improve carrier mobility; and the intrinsic thermodynamic stability of TiO2 ensures the long-term operational stability of the photoelectrode based on this green, cadmium-free, highly efficient, and stable electron transport layer in the electrolyte.

[0080] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a green, cadmium-free and highly efficient stable electron transport layer, characterized in that, The green cadmium-free and high-efficiency stable electron transport layer is prepared by atomic layer deposition, and comprises the following steps. A clean substrate is taken, and ZnO deposition procedures and TiO2 deposition procedures are alternately performed on the substrate for several times. 2.The method for preparing a green, cadmium-free, and high-efficiency stable electron transport layer according to claim 1, characterized in that, Each ZnO deposition procedure comprises several ZnO pulse procedures, and the thickness of ZnO deposited in each ZnO pulse procedure is 0.1±10 nm; Each TiO2 deposition procedure comprises several TiO2 pulse procedures, and the thickness of TiO2 deposited in each TiO2 pulse procedure is 0.07±10 nm.

3. The method according to claim 2, wherein, the ratio of the number of ZnO pulse procedures in each ZnO deposition procedure to the number of TiO2 pulse procedures in each TiO2 deposition procedure is 1-9:1; the ZnO pulse procedure comprises a 40-80 ms zinc source pulse, an 80-120 ms oxygen source pulse and a 5-10 s N2 blowing pulse; the TiO2 pulse procedure comprises a 40-80 ms titanium source pulse, an 80-120 ms oxygen source pulse and a 5-10 s N2 blowing pulse; the N2 blowing procedure between each ZnO deposition procedure and each TiO2 deposition procedure comprises 15-25 s; the zinc source is diethyl zinc, dimethyl zinc or a zinc amide compound; the titanium source is titanium tetrachloride, a chlorinated alcohol salt of titanium or trimethyl (cyclopentadienyl) titanium; and the oxygen source is deionized water or ozone. 4.The method for preparing a green, cadmium-free and high-efficiency stable electron transport layer according to claim 3, characterized in that, The temperature of the delivery pipe for delivering the zinc source, the titanium source and the oxygen source is 80-120 ℃, and the temperature during deposition is 150-190 ℃.

5. A green cadmium-free and highly efficient stable electron transport layer, characterized in that, The green cadmium-free and high-efficiency stable electron transport layer is prepared by the method according to any one of claims 1-4, or comprises a ternary compound (Zn, Ti)O.

6. The green cadmium-free and high-efficiency stable electron transport layer in the application of a photoelectrode for water splitting to produce hydrogen.

7. A photoelectrode for hydrogen production by water photolysis, characterized by comprising: The heterojunction comprises the green cadmium-free and high-efficiency stable electron transport layer and a light absorption layer according to claim 5.

8. The photoelectrode for hydrogen production by water splitting according to claim 7, wherein The thickness of the electron transport layer is 15-30 nm.

9. The photoelectrode for hydrogen production by water splitting according to claim 7, wherein The light absorption layer is an Sb2Se3 light absorption layer with a thickness of 1000-1500 nm.

10. A method for producing a photoelectrode for hydrogen production by water splitting according to any one of claims 7 to 9, characterized by, The method comprises the following steps: preparing an electron transport layer on the light absorption layer, and then treating the electron transport layer under vacuum at 250-350 ℃ for 30-50 min. The method comprises the following steps: preparing an electron transport layer on the light absorption layer, and then treating the electron transport layer under vacuum at 250-350 ℃ for 30-50 min.

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