Enhanced carrier management via optimized SnO2 preparation and film coverage for improved device performance

Abstract

Optimized electron transport layers (ETLs) can highly promote charge extraction and reduce carrier depopulation. Herein, tin oxide (SnO2) nanocrystals were prepared with the addition of citric acid to suppress SnO2 aggregation and achieve complete film coverage. The dense and uniform SnO2 films with smaller grain sizes will apparently enhance the external quantum efficiency and alleviate the J–V hysteresis behavior. The improved SnO2 film coverage can also passivate traps at ETL/perovskite interfaces and markedly suppress charge recombination to promote rapid carrier injection from perovskite to SnO2. Surely, the optimized SnO2 shows better electrical properties and device performance than Alfa-SnO2. In addition, the diblock-polymer of (PEO)120-(PPO)30 was incorporated into perovskite films to passivate defects and improve device stability. A power conversion efficiency of 23.12% [a VOC of 1.164 V, a JSC of 24.46 mA cm−2, and a fill factor (FF) of 0.812] for the best-performing device is achieved. The charge dynamics (separation, transport, and extraction) were also analyzed using characterization techniques. The optimized device will largely enhance carrier management and light-harvesting performance, and the controlled SnO2 can also open up an effective way to achieve scalable preparation and commercialization of perovskite solar cells.