The Research On Pyridyl-imidazole Homologues Additives Towards High Performance Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells（PSCs）have obtained the breakthrough in just 8 years,and the photoelectric conversion efficiency is above 22.7%.PSCs are bound to develop in the direction of industrialization in a long term.In terms of current situation of the perovskite,the photoelectric conversion efficiency has reached the standard of the industrialization.However,the the long-term stability problem exposed to sensitive conditions becomes the key factors of restricting its development.Therefore,improving the stability of the perovskite solar cells becomes the focus of current research work.The sensitive interface of hole transport layer（HTL）/perovskite layer and perovskite layer/electronic transport layer（ETL）are the mainly interface in the PSCs.In the traditional structure of the perovskite solar cells,the interface between HTL and perovskite layer is particularly important because the interface is the main channel of perovskite film exposed to the sensitive conditions,such as water and oxygen.In addition,the high defect state density at the interface leads to the recombination of charges.All of the above problems affect the PSCs performance.Focused on these problems,we introduced Co-complex tris[2-（（1H-pyrazol-1-yl）-4-tert-butylpyridine）cobalt（Ⅲ）tris（bis（trifluoromethylsulfonyl）imid e）]（FK209）in the HTL,and studied the mechanism of Co-complex at the interface.Co-complex enching at the interface shielded the defect state of the interface,improved the ability of charge collection and transportation,depressed the charge recombination,which leads to an increased current density,open voltage and fill factor of the PSCs devices.We obtained the optimal power conversion efficiency of 17.34%by optimizing the Co-complex doping ratio.Moreover,we found that the doping of Co-complex into the HTL significantly improved the stability under a sensitive atmosphere.In addition to the interface of perovskite/HTL,the defects in the internal grain boundary of the perovskite thin film also restrict the improvement of the power conversion efficiency and thermal stability of the devices.Our work mainly focused on the thermal stability of the perovskite thin film induced by its defects.We assembled 2-（1H-pyrazol-1-yl）pyridine（PZPY）and 3D perovskite precursor system(Cs_0.04MA_0.16FA_0.8PbI_0.85Br_0.15),which allows to obtain a series of 1D-3D lead halide hybrid perovskite materials by in-situ growth.The detect density on the grain boundary of the hybrid 1D-3D perovskite thin films was lowered compared to the 3D perovskite thin films,because of the flexible structure and superior thermal stability.In addition,1D perovskite thin films could block the ion-migration channels of A site cations in heterojunction,which depressed the irreversible degradation of 3D perovskite thin films caused by the widely migration of A site cations,and realized the thermodynamically self-repairing capabilities of the perovskite device.Our findings provided new insights into ongoing development efficient and stable perovskite solar cells,and promoted the process of its industrialization.