Obviously decreased hysteresis index originated from enhanced grain size with ETL modification for improved performance of perovskite solar cells

Perovskite demonstrates ideal properties for photovoltaic devices, which has attracted extensive attention in the last decade. However, defects in the bulk and interfaces always lead to inferior behavior such as high hysteresis index (HI), poor stability, low carrier transportation, and so on. Since electron transport layer (ETL) has a great influence on the crystallinity of perovskite that would induce grain boundaries and defects, in this paper, an organic silane oxide coupling agent (vinyl tri (2-methoxyethoxy) silane, VTMES) was used to modify the ETL of tin oxide. The result shows that doping VTMES in SnO₂ can effectively improve the wettability of SnO₂ surface and promote the growth of perovskite crystals at its interface. The average grain size of perovskite promotes from 560 to 857 nm, helping to facilitate carrier transport and reduce leakage current. The HI of the VTMES modified device greatly reduces from 16.1 to 3.9%. The optimal power conversion efficiency (PCE) increases from 19.23 to 21.16% with promoted stability. This work provides a new path for perovskite devices to decrease HI with obviously enhanced grain size by modification of ETL.