The Preparation Of 2D?C₆H₅C₂H₄NH₃?₂?FA?_n-1Pb_nI_3n+1Based Perovskite Films And Their Applications In Solar Cells

Poor humidity stability of perovskite solar cells?PSCs?is one of the important factors restricting their commercialization.Therefore,two-dimensional?2D?layered perovskite solar cells with high stability have attracted much attention in recent years.To improve the photoelectric conversion efficiency?PCE?of 2D perovskite solar cells,we put forward a two-step approach to fabricate high-quality 2D?PEA?₂?FA?_n-1Pb_nI_3n+1perovskite films.We drop FAI solution on the?PEA?2PbI4 and unreacted of PbI2 films to obtain?PEA?₂?FA?_n-1Pb_nI_3n+1.The PCE of 2D perovskite solar cells were improved by adjusting the microstructure of perovskite films and optimizing the performance of the electron transport layer.Futhermore,the effects of Cs⁺doping on?PEA?₂?FA?_n-1Pb_nI_3n+1 films were studied.The main conclusions of this paper are as follows:?1?The novel two-step method was utilized to obtain?PEA?₂?FA?_n-1Pb_nI_3n+1.At first,we obtain the mixture of PbI₂ and?C₆H₅C₂H₄NH₃?₂PbI₄ and then drop FAI solution onto the films of?PEA?2PbI4 and unreacted PbI2.By optimizing the stoichiometric ratio of PEAI and PbI₂,the concentration and amount of FAI,and the heat treatment process,high-quality 2D?PEA?₂?FA?_n-1Pb_nI_3n+1 perovskite films can be obtained as a meaningful light absorber material with good orientation,dense morphology,and strong light absorption.The corresponding perovskite solar cells have a photoelectric conversion efficiency up to 11.46%.At the same time,due to the hydrophobic of large size ?C₆H₅C₂H₄NH₃?⁺,?PEA?₂?FA?_n-1Pb_nI_3n+1n+1 film shows excellent moisture stability.When exposed to 60%RH for 900 hours,the photoelectric conversion fficiency of the unencapusulation battery can maintain 86%of the initial PCE.?2?To explore the influence of electron transport layers on?PEA?₂?FA?_n-1Pb_nI_3n+1 perovskite solar cells,TiO₂&SnO₂ thin films were prepared by the sol-gel method.The results show that laminated TiO₂&SnO₂ thin films are more conducive to the transport of carriers in?PEA?₂?FA?_n-1Pb_nI_3n+1 films than the traditional TiO₂ layer.The magnetic hysteresis effects of?PEA?₂?FA?_n-1Pb_nI_3n+1perovskite solar cells were also improved due to the layered TiO₂&SnO₂ film is conducive to the extraction of electron-hole pairs in the?PEA?₂?FA?_n-1PbnI3n+1film.?3?The effects of Cs⁺doping on?C₆H₅C₂H₄NH₃?₂?FA?_n-1Pb_nI_3n+1 were investigated.When the doping amount of Cs⁺is less than 4 wt%,the growth of?C₆H₅C₂H₄NH₃?₂?FA?_n-1Pb_n I_3n+1 films were promoted,and the growth of?C₆H₅C₂H₄NH₃?₂?FA?_n-1Pb_nI_3n+1n+1 was inhibited when the doping amount of Cs⁺is greater than 4 wt%.The photoelectric conversion efficiency of the obtained perovskite solar cells increased to 9.88%,which was higher than the PCE of undoped.When the doping amount of Cs⁺was more than 4 wt%,the PCE of Cs_x-2D decreases.According to impedance spectrum analysis,the main reason that Cs⁺doping increased the PCE of the device is that Cs⁺doping reduced the charge transfer impedance of Cs_x-2D perovskite films.