C60 additive-assisted crystallization in CH3NH3Pb0.75Sn0.25I3 perovskite solar cells with high stability and efficiency

Abstract

The development of hybrid tin (Sn)–lead (Pb) perovskite solar cells likely tackles the toxic problem with the power conversion efficiency (PCE) exceeding 17%. However, the stability problems, e.g. hysteresis effect, degeneration and oxidation, appear to be the bottleneck that limit its further development. Here, we innovatively introduced C₆₀ at the grain boundaries throughout the CH₃NH₃Pb_0.75Sn_0.25I₃ (MAPb_0.75Sn_0.25I₃) thin film, playing a role not only in in situ passivating the interfaces and reducing the pinholes of perovskite thin films, but also in preventing the penetration of moisture and oxygen from ambient atmosphere. Electrochemical impedance spectroscopy (EIS) illustrated that the recombination lifetime of both the bulk and surface of MAPb_0.75Sn_0.25I₃ thin films was increased by additive incorporation of C₆₀. Dark I–V results for the electron/hole-only devices showed that the charge trap-state density decreased with C₆₀ additive incorporated into the hybrid Sn–Pb perovskite thin films. Importantly, the hybrid Sn–Pb perovskite solar cells modified with C₆₀ additive were demonstrated to have superior stability and efficiency when exposed to the ambient environment without encapsulation.