SnO2 electron transport layer modified by F/N-doped graphdiyne and in situ XRD and in situ XAFS exploration on its effect on perovskite active layer

Electron transport layer (ETL) plays an important role in the perovskite solar cells. The graphdiyne oxide (GDYO), nitrogen-doped GDYO (NGDYO) or fluorinated GDYO (FGDYO) was added into SnO2 ETL, respectively, which optimized the properties of SnO2 layer itself and the interface between ETL and perovskite layer, and then affected the growth of perovskite. The mechanism was systematically explored by using in situ synchrotron radiation technology combined with conventional characterization methods. Though NGDYO-SnO2 enhanced the properties such as conductivity and energy level of ETL, FGDYO-SnO2 showed the best crystallization. By tracking the growth process of SnO2, PbI2 or perovskite by in situ XRD and the chemical bonds on the interface between ETL and active layer by in situ XAFS, it was found that the stronger interaction between the doped SnO2 with PbI2 inhibited PbI2 crystallization in perovskite layers and gave more opportunity for PbI2 precursor to form perovskite, making perovskite to have better crystallization. Finally, the optimized performance of device was achieved.