Preparation Of High Quality CsPbI₃/CsPbBr₃ Films And Optimization Of Device Performance Based On Carbon Electrode

After decades of development,the photoelectric conversion efficiency(PCE)of perovskite solar cells(PSCs)increased from 3.8%to 25.7%,making it the most popular third-generation photovoltaic device.All-inorganic CsPbX₃(X=Cl,Br,I)PSCs have been widely researched because of its simple structure,suitable band gap and excellent carrier transport characteristics.However,there are also some problems for CsPbX₃PSCs:Firstly,the thermal decomposition of organic hole transport materials such as spiro-OMe TAD(spiro)is a significant factor affecting the long-term stability of CsPbX₃device.Besides,the poor quality of film leads to more interface recombination,which makes the low performance.Therefore,it is very important to prepare CsPbX₃photovoltaic devices with high efficiency and high stability.To solve these problems,we used carbon electrode(Carbon paste,work function of 5.0 e V)to replace silver(Ag)and Spiro to improve its stability,and optimized the spinning coating process and interface modification of the film to improve the efficiency of PSCs.1)To solve the problems of the poor film quality and low performance of CsPbBr₃device,the spin-coating methods are optimized,that is,multi-step spin coating Cs Br to improve the content of Cs Br in CsPbBr₃film.When the layer of Cs Br is 5,the defect of film is less and the film quality is higher.And carbon electrodes are used to instead of Ag electrodes to optimize the energy level,so that the PCE of the carbon electrode CsPbBr₃device reaches 6.35%,which is 0.55%higher than that of using Ag electrode.2)CsPbI₃PSCs were prepared by using carbon electrode instead of Ag and spiro.And TPAI(tetrabbutylammonium iodide)was introduced to modify CsPbI₃film,which effectively reduced the interfacial carrier recombination,improved the efficiency of carrier separation and extraction,and made the PCE up to 15.07%,and further enhanced the stability.3)In order to stable the CsPbI₃phase structure to improve the stability of CsPbI₃film,the precursor solution was doped with ethylenediammonium cation(EDA²⁺).It is investigated that when n=40 for two-dimensional(EDA)Cs_n-1Pb_nI_3n+1perovskite optimized with TPAI,the best PCE of 10.15%is obtained.