Chiral cation promoted interfacial charge extraction for efficient tin-based perovskite solar cells

Efficient Sn-based perovskite solar cell device with power conversion efficient of 10.73% and low hysteresis effect is reported, where chiral cation is adopted to promote the formation of 2D/3D structure of the perovskite film and facilitate the selective hole transportation at the interface of the device. Pb-free Sn-based perovskite solar cells (PSCs) have recently made inspiring progress, and power conversion efficiency (PCE) of 14.8% has been achieved. However, due to the energy-level mismatch and poor interfacial contact between commonly used hole transport layer (i.e., poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS) and FASnI 3 film, it is still challenging to effectively extract holes at the interface. Owing to the p-type nature of Sn-based perovskites, the efficient hole extraction is of particular significance to improve the PCE of their solar cells. In this work, for the first time, the role of chiral cations, α -methylbenzylamine ( S -/ R -/ rac -MBA), in promoting hole transportation of FASnI 3 -based PSCs is demonstrated. The introduction of MBAs is found to form 2D/3D film with low-dimensional structures locating at PEDOT:PSS/FASnI 3 interface, which facilitates the energy level alignment and efficient charge transfer at the interface. Importantly, chiral-induced spin selectivity (CISS) effect of R -MBA 2 SnI 4 induced by chiral R -MBA cation is found to further assist the specific interfacial transport of accumulated holes. As a result, R -MBA-based PSCs achieve decent PCE of 10.73% with much suppressed hysteresis and enhanced device stability. This work opens up a new strategy to efficiently promote the interfacial extraction of accumulated charges in working PSCs.