Multifunctional\nConjugated Polyphenol “Bridge”\nCapped the Upper Interface of Highly Efficient and Stable Inorganic\nPerovskite Solar Cells Fabricated in Air

Carbon-based\nall-inorganic perovskite solar cells (C-PSCs) are\npromising alternatives compared with conventional organic–inorganic\nhalide PSCs because of their good thermal stability. However, low\ncarrier transport efficiency and energy level mismatch of the upper\ninterface of the device limit the further improvement of power conversion\nefficiency (PCE), and all-inorganic perovskites are extremely sensitive\nto oxygen and humidity, which seriously damages the long-term stability\nof the device. Upper interface modification is an effective solution\nto improve the PCE and the stability of devices. Unfortunately, many\ntraditional interface modifiers exhibit insulated and hygroscopic\ncharacteristics, which may be harmful to the performance of the device.\nHerein, a multifunctional conjugated polyphenol “bridge”\nstrategy was adopted on the upper interface of the device fabricated\nin air, that is, stilbene and polyhydroxy stilbene were capped on\nperovskite. The results demonstrate that they can effectively enhance\nthe energy level alignment, improve charge transport, passivate defects,\nsuppress nonradiative recombination of interface, and resist oxygen\nand moisture in air, and the positive effects of modification become\nmore and more pronounced with the increment of the number of hydroxyl\ngroups. The PCE of PSCs was improved from 11.10 to 13.10% after modification.\nIn addition, the unencapsulated modified devices exhibited better\nstability than the control devices under different environmental conditions.