Negligible hysteresis planar perovskite solar cells using Ga-doped SnO2 nanocrystal as electron transport layers

Planar perovskite solar cells (PSCs) have been demonstrated as a promising architecture for efficient, large-scale, flexible and tandem solar cell. To date, unfortunately, most planar PSCs suffer from current-voltage hysteresis, which derives from interface mismatch, surface defects , ion migration, and ferroelectric property et al. Here, we demonstrate a facile strategy to significantly reduce the hysteresis and improve the performance of planar PSCs by doping gallium (Ga) into tin oxide (SnO 2 ) nanocrystal electron-transport layer using low-temperature solution‐processed method. It is revealed that the Ga-doped SnO 2 ETL owning better band alignment with the perovskite absorption layer , which is helpful for electron extraction. It is found that gallium doping severely decreases the trap state density in SnO 2 , leading to a lower recombination rate and negligible hysteresis. With the optimized doping concentration of Ga ions , the champion device achieves a highest PCE of 18.18% and the hysteresis index is reduced from 23.9% to 1.7%.