Fluorinated Interfaces for Efficient and Stable Low-Temperature Carbon-Based CsPbI_2Br Perovskite Solar Cells

摘要

Carbon-based inorganic perovskite solar cells (C-PSCs) have attracted intensiveattention owing to their low cost and superior thermal stability. However,the bulk defects in perovskites and interfacial energy level mismatch seriouslyundermine their performance. To overcome these issues, a multifunctional dualinterfaceengineering is proposed with a focus on low-temperature CsPbI_2BrC-PSCs, where the potassium trifluoroacetate (KTFA) and the 4-trifluorophenylmethylammonium bromide (CF3PMABr) are introduced beneath and on topof the perovskite layer, respectively. It is found that TFA- ions locate at theSnO_2/CsPbI_2Br interface, whereas a small amount of K+ ions diffuse intoperovskite lattice to participate in nucleation and crystallization, resulting in morefavored interfacial energy level alignment, improved film quality, passivatedinterfacial defects, released interfacial strain, as well as suppressed chargerecombination and ion migration. Meanwhile, the CF_3PMABr passivates I/Brvacancies and forms 2D perovskite capping layer to facilitate hole extractionat the CsPbI_2Br/carbon interface. As a result, a remarkable power conversionefficiency (PCE) of 14.05 with an open-circuit voltage of 1.273 V is achieved. Tothe best of the authors’ knowledge, it is currently the highest PCE reported forlow-temperature CsPbI_2Br C-PSCs. Furthermore, the nonencapsulated deviceexhibits improved moisture, thermal, and illumination stability in ambient air.