Passivation and energy-level change of the SnO2 electron transport layer by reactive titania for perovskite solar cells

Reactive anatase titania (TAc) are incorporated into SnO 2 to form a single TAc-SnO 2 electron transport layer (ETL) for mixed-cation perovskite solar cells (PSCs). The TAc-SnO 2 layer is prepared in a low-temperature process by the advantage of high crystallinity and surface reactivity of TAc. The influence and mechanism of the TAc incorporation on the photovoltaic performance of PSCs are investigated. The TAc-SnO 2 ETL presents rapid electron transfer, low trap density, high charge recombination resistance, low hysteresis and good stability. The 2.5-wt% TAc incorporation reveals the highest power conversion efficiency of 20.12%, a 19%-fold enhancement compared to the pristine cell with the SnO 2 ETL. The enhancement arises from the fact that the TAc can fill up breaching in the pristine SnO 2 layer and adjust the ETL energy level. The carboxyl groups of TAc facilitate the formation of solid bonding among SnO 2 /TAc colloids and prevent ions from accumulation at the interface of ETL/perovskite. The work provides a facile way to fabricate a low-temperature, single-layer and effective ETL for highly efficient PSCs. • Reactive anatase TiO 2 (TAc) was incorporated into electron transport layer (ETL). • Carboxyl groups of TAc facilitate the formation of strong bonding among colloids • TAc can fill up breaching in SnO 2 layer and adjust the ETL energy level. • Power conversion efficiency reaches to 20.12%. • A facile way to fabricate a low-temperature, single-layer, and effective ETL.