Preparation Of CdTe Solar Cell And The Application In Hydrogen Production By Water Splitting

Building a photovoltaic water electrolysis system to convert solar energy into hydrogen energy with high energy density can achieve a more efficient use of solar energy.High efficiency,high stability and low cost are the necessary factors for application of photovoltaic water electrolysis system in practical production.Therefore,a photovoltaic water electrolysis system has high requirements on conversion efficiency,production cost,practicability of the solar cell and catalytic performance,cost and catalytic stability of the catalytic electrode.CdTe thin film solar cell has the advantages of stable performance,simple structure,good low light response and so on.Because of the transparent mechanism,it can be used as building curtain wall and skylight to realize the integration of photovoltaic buildings.On the other hand,electrolysis of water is carried out under the low voltage,which reduces the number of electrode etching of CdTe solar cell,simplifies the production process of CdTe solar cell and reduces its production cost,which makes CdTe solar cell become an excellent choice for the power supply of photovoltaic water electrolysis system.In the current research of CdTe thin film solar cell,CdTe solar cell of high-performance is generally prepared by high energy consumption technologies such as vapor transport（VTD）and near space sublimation（CSS）,the production cost is still high,while the low-cost electrochemical deposition method for CdTe thin film is faced with problems such as low deposition rate and corrosion of window layer in acid system,and the research on electrochemical deposition of CdTe thin film in various alkaline systems has not been able to produce Cd Te thin film with high quality.In the aspect of catalytic electrode,OER process is the bottleneck of hydrogen production due to the sluggish kinetics for the four-proton-coupled electron transfer.In the practical application of photovoltaic water electrolysis system,noble metal catalysts such as IrO₂ and RuO₂ are obviously not suitable.It is very important to find a OER catalyst with high catalytic performance and abundant reserves on earth.The application of popular substrate materials such as carbon cloth and Ni foam in the research of OER catalysts are also seriously restricted in large-scale photovoltaic water electrolysis systems in terms of the conductivity and cost.Exploring a high conductivity and low cost OER substrate material is also a problem that must be solved in the practical application of photovoltaic water electrolysis system.This paper focuses on the problems of CdTe thin film cell and catalytic electrode in water electrolysis system.The main research contents and innovations are as follows:1.The study of electrodepositing CdTe thin film in TMAH organic alkaline solution（1）The effect of pH and NTA/Cd²⁺complexing ratio on the structure and composition of CdTe film was studied in TMAH organic alkaline solution system.The pH of solution not only affects the dissolution,diffusion,adsorption and reduction rate of TeO₂ to control the amount of Te in the film-forming reaction,but also determines the Cd content in the CdTe film by affecting the complexing ability of NTA to Cd²⁺;different complexing ratios can control the supply of Cd²⁺in the CdTe film-forming reaction,and the different concentration of Cd²⁺at the reaction interface also affected the adsorption of TeO₃^2-.The high quality CdTe thin film was prepared under the condition of pH=9.85 and 14:1 NTA/Cd²⁺complex ratio,and the CdTe solar cell with conversion efficiency of 8.2%was assembled.（2）The interface structure of CdTe thin film solar cell was optimized by using CdSe intermediate layer introduced by electrochemical deposition to reduce the lattice mismatch at the interface,so as to reduce the cracks,pores and other defects caused by the interface stress after annealing.However,after adding CdSe interlayer,the change of reaction interface leads to the increase in the defects in CdTe film layer.2.The study of electrodepositing CdTe thin film in acid solutionCdTe thin film also was electrodeposited in acid system.After annealing,compact,pore free and high crystallinity CdTe thin film with 2μm thick was obtained.The cell efficiency is10.6%,the short-circuit current is 34 mA/cm²,the open circuit voltage is 639 mV,the filling factor is 48.9%and the external quantum efficiency can reach to 90%.This solar cell is used as a power source in the photovoltaic water electrolysis system.3.Structure design and electrocatalytic performance of the OER electrodeThe coaxial three-layer（Ni,Fe）O_xH_y/Ni/Cu mesh electrode structure was designed as the OER electrode of the photovoltaic water electrolysis system.The Ni layer was electroplated on the Cu mesh,and then the（Ni,Fe）O_xH_y catalyst was grown on the substrate by a solvothermal method.The electrode exhibits excellent OER activity in alkaline electrolyte（1m KOH）:at the current densities of 10 and 50 mA/cm²,the overpotentials are 199 and 250 mV,respectively,and it has a good long-term stability of over 72 hours.In the electrode structure,the low cost and high conductivity Cu mesh substrate improves the charge transfer rate in OER process;the electroplated Ni layer prevents the oxidation of Cu mesh to improves the electrode stability,and the fresh Ni layer with high surface activity improves the bond strength between the catalyst and the substrate.4.Preliminary construction of solar cell photovoltaic water electrolysis systemThe CdTe thin film solar cell prepared by acid system deposition is used as the power supply,（Ni,Fe）O_xH_y/Ni/Cu mesh electrode is used as the OER electrode,Pt electrode is used as HER electrode,and then the CdTe thin film solar cell photovoltaic water electrolysis system is preliminarily constructed and assembled.Under the simulated sunlight,CdTe thin film solar cell provides 1.7V voltage,making the photovoltaic water electrolysis system reach an overall water splitting current density of 206 mA/cm²,and maintain excellent stability of overall water splitting for over 72 hours.