HClO4-assisted fabrication of SnO2/C60 bilayer electron-transport materials for all air-processed efficient and stable inverted planar perovskite solar cells

In inverted planar perovskite solar cells (PSCs), fullerene (C 60 ) and its derivatives are widely utilized as electron-transport layer (ETL) materials, however, possess some drawbacks such as low electron mobility , interfacial degradation, and relatively inferior stability. In this work, we develop a facile thermal annealing-free hydrothermal route to synthesize high-crystalline SnO 2 nanocrystals through controlling the crystallization process with HClO 4 . An interlayer of SnO 2 nanocrystals is inserted between C 60 ETL and Ag electrode. The SnO 2 interlayer can not only serve as an ETL to help improve electron extraction and transport but also act as a passivation/barrier layer to prevent oxygen and moisture ingress and ion migration. Based on the p-i-n structure of fluorine-doped tin oxide (FTO)/NiO x /MAPbI 3 /C 60 /SnO 2 /Ag, the power conversion efficiency (PCE) of the champion device is up to 16.36% with almost negligible hysteresis . The unencapsulated inverted PSCs retain more than 80% of its initial PCE value after storage in atmosphere for 90 days (>2100 h), and degrade only about 20% its initial efficiency after 41 h under heating at 85 °C. More important, all the preparation processes are performed under ambient conditions. Our work provides a viable strategy for assembling highly efficient and stable inverted PSCs in the air.