Interfacial Engineeiring Of Perovskite Nanocrystal Solar Cells

In this project,we carefully investigated the photovoltaic properties of emerging perovskite nanocrystal materials and further improved their solar cell efficiency through rational interfacial design.The project is able to be divided into the following three parts:Firstly,we blended conjugated polymer with perovskite nanocrystals to fabricate hybrid-heterojunction buffer layer by solution process.The introduction of polymer mainly plays two roles:1.Adjust the hydrophilicity and hydrophobicity of the film surface to benefit the deposition of hole transport layer;2.The bulk heterojunction structure can regulate the carrier dynamics at the interface.By comparing several conjugated polymers including PTB7,PBDB-T,PTP8 and PTB7-Th,we found that the energy level alignment is a key factor which can affect device performance.Moreover,we further verified the universality of this device structure.Both CsPbI3 and FAPbI3 perovskite nanocrystals were used to research solar cells,achieving an efficiency of 13.8%and 13.2%,respectively,situating the forefront of all reported perovskite nanocrystal solar cells.Besides,the hydrophobicity of the polymer improved the stability of the devices,showing the importance of this hybrid interface buffer layer.Secondly,we successfully fabricated organic-inorganic hybrid devices with polymer as the electron donor and perovskite nanocrystal as the electron acceptor,considering that the energy levels of CsPbI3 and FAPbI3 perovskite nanocrystal are similar to that of the traditional organic electron acceptor PCBM.Through apparent fluorescence quenching and decrease of exciton lifetime,we have demonstrated the existence of charge transfer between organic polymer and perovskite nanocrystal We finally realized the best power conversion efficiency of 10%based on this type of hybrid heterojunction by optimizing the thickness and component ratio of the hybrid layer.This value is also one of the highest records among the reports based on this device structure.Thirdly,mixed solvents as "anti-solvent" were applied to control the interface of the MAPb13 bulk film.The MAPbI3 bulk film deposited by mixed "anti-solvent"passivation process has a denser film morphology,resulting in reduced grain boundaries and enhanced carrier extraction as well as transport capabilities at the interface.By optimizing the ratio of mixed solvents and the time of "anti-solvent"treatment,the MAPbI3 solar cell device achieved the maximum photoelectric conversion efficiency of 21.2%,which showed a significant improvement over the 19.6%efficiency of the single solvent processed device.These results indicate that the "anti-solvent" treatment with mixed solvents can produce perovskite thin film with higher quality and lead to enhanced efficiency of perovskite solar cells.