Preparation Of Efficient And Stable Inorganic CsPbI₂Br Perovskite Solar Cells In Air

The metal halide perovskite solar cells(PSCs)have attracted much attention due to their constantly updated power conversion efficiency(PCE)and low preparation cost.The volatile organic components in organic-inorganic hybrid perovskite materials lead to poor photo and thermal stability.The replacement of organic cations with inorganic cations,such as Cs,could overcome the instability issue of the organic-inorganic hybrid perovskite to endow the perovskite with better compositional stability.Therefore,inorganic PSCs based on CsPbX3(X:I,Br or mixed halides)have been developed rapidly in the past few years.However,the preparation of high-efficiency inorganic PSCs in ambient air is still intractable,especially under high humidity conditions,since the crystallization,film morphology and crystalline phase of inorganic perovskites are highly sensitive to moisture.Therefore,high efficiency PSCs are mainly prepared in inert environment.This has led to significant concerns associated with the long-term stability and manufacturing costs,which are some of the major limitations for the commercialization of inorganic PSCs.This thesis focused on three aspects,the structure of the device,fabricate process and precursor engineering,respectively,to help the future development of the preparation of all inorganic CsPbI2Br PSCs in ambient air.The main content is as follows:(1)In order to improve the efficiency and stability of CsPbI2Br PSCs prepared in air,the structure of the PSCs was optimized.Firstly,a SnO2/TiO2 composite electron transport layer(ETL)was introduced to replace TiO2 layer.Compared with the original ETL,using this composite ETL could reduce the defects of CsPbI2Br perovskite film,improve the efficiency of electron hole separation at the interface between ETL and perovskite,and reduce the carrier recombination.Then,PTAA/Spiro-OMeTAD,a composite hole transport layer(HTL),was introduced to replace the pristine Spiro-OMeTAD layer,then to improve PCE and the stability of the device.Finally,we had fabricated all inorganic CsPbI2Br PSCs with composite ETL and composite HTL structure in ambient air,which improved PCE from 11.20%to 12.26%.(2)In order to solve the problem that the inorganic CsPbI2Br perovskite films can be easily affected by air during the preparation process,a low temperature hot-casting method was introduced to prepare perovskite film.In this work,perovskite films were prepared in air and exhibited a high quality and thickness,then the CsPbI2Br PSCs were prepared in air,which show comparable performance with that of device prepared by the traditional methods in N2 atmosphere.Finally,the CsPbI2Br devices exhibited a PCE of 14.56%and a simplified preparation process.(3)At last,a novel precursor combination(HCOOCs and HPbX3)had been developed to prepare high quality CsPbI2Br films in fully ambient air by a one-step and antisolvent-free process,which offers a wide processing window for air preparation and tackles the instability issue of CsPbI2Br precursor film during the fabrication and annealing process.Notably,inorganic PSCs prepared in atmosphere with 30%RH and 91%RH exhibited PCEs of 16.1%and 15.1%,respectively,which were the highest among inorganic PSCs prepared in medium-and high-humidity atmospheres.The unencapsulated CsPbI2Br PSCs aged in the ambient air for more than 800 hours,and still maintained 92%initial efficiency.