Defect Passivation In Metal Halide Perovskite Solar Cells

For the last decade,perovskite solar cells have attracted much attention because of their high optical absorption coefficient,large carrier diffusion coefficient and adjustable band gap.The cell photovoltaic conversion efficiency increased rapidly from an initial efficiency 3.8%to 25.7%.Perovskite solar cells（PSCs）are being considered not only for large-scale commercial applications,but also for space applications.Improving conversion efficiency and stability is a necessary condition for the marketization of PSCs。Numerous researchers have focused their efforts on exploring the use of passivation engineering to reduce internal defects in cells,thereby improving cells efficiency and stability。Regarding the space applications of PSCs,which are affected by various types of radiation such as rays and protons in the space environment,not only high conversion efficiency is required,but also good stability and irradiation resistance should be considered.Therefore,how to prepare PSCs with high efficiency,stability and good radiation resistance has become a research goal in space applications.The key issue of obtaining PSCs that meet the requirements of space applications lies in the preparation of uniformly dense and defect less dense chalcogenide absorber layers,thus improving their stability under solar irradiation and space radiation.Meanwhile,exploring the damage mechanism and reinforcement method of chalcogenide cells under space proton irradiation is of great value for the space application of such cells.To address the above issues,the following studies were done in this research:A new type of perovskite solar cell with high efficiency,stability,good radiation resistance and low cost has become the research object.The key to the research of perovskite cells is to improve the stability of the cells under solar irradiation and proton irradiation.As well as the preparation of homogeneous perovskite absorber layer and enhancement of carrier mobility of the transport layer,reduction of compounding in order to facilitate the preparation of high efficiency large area modules.To address the above issues,this thesis has done the following research:Firstly,in this thesis,additive engineering was used to separately dope a small amount of KF,KCl,KBr and KI into the electron transport layer.Through the test and characterization,it was found that the grain size of the perovskite was significantly increased after doping,the carrier lifetime was improved,and the photoelectric conversion efficiency was increased from 19.88%to 20.96%.The results show that the K⁺in the four additives KF,KCl,KBr and KI can not only diffuse into the perovskite crystal structure,but also passivate the defects in the perovskite grains and effectively improve the crystallinity of the perovskite film structures,reducing conformance defects and improving device efficiency and stability.Secondly,a dithizone（DTZ）modified layer is inserted between the perovskite absorber layer and the hole transport layer to reduce the recombination rate of carriers at this interface.By analyzing the test results,the insertion of DTZ layer improves the battery parameters V_ocand FF,and the conversion efficiency also increases from 16.96%to 19.67%.The tracking test results of the storage stability of the perovskite battery show that the battery stability is also greatly improved.After500 hours,the cell efficiency remained at 80%of the initial efficiency.The results show that DTZ can reduce the enrichment of Pb I₂on the surface,interface defects and Non-radiative carrier recombination,thereby effectively improving the efficiency and stability of perovskite cells.Finally,the encapsulated perovskite solar cells were subjected to 150 Ke V and10 Mev proton irradiation experiments to study the effect of proton irradiation at different fluence points and irradiation times on the photovoltaic performance of perovskite solar cells.The experimental results suggest that the perovskite solar cell has excellent radiation resistance.The results show that PSCs have good radiation resistance.With the increase of proton radiation fluence,the basic photovoltaic parameters have a weak decay trend,and the short-circuit current density is more sensitive to proton radiation than other photovoltaic parameters.The proton irradiation effect can achieve PSCs defect passivation,and further characterization and research are needed.