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

Abstract

Reactive anatase titania (TAc) are incorporated into SnO2 to form a single TAc-SnO2 electron transport layer (ETL) for mixed-cation perovskite solar cells (PSCs). The TAc-SnO2 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-SnO2 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 SnO2 ETL. The enhancement arises from the fact that the TAc can fill up breaching in the pristine SnO2 layer and adjust the ETL energy level. The carboxyl groups of TAc facilitate the formation of solid bonding among SnO2/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.