Constructing binary electron transport layer with cascade energy level alignment for efficient CsPbI 2 Br solar cells

Recently, all-inorganic perovskite solar cell (PSC) has attracted an increasing research attention due to its excellent thermal stability and suitable band gap for tandem devices. Herein, a highly efficient all-inorganic PSC with CsPbI2Br as light absorption material is assembled by employing a binary electron transport layer (ETL), which consists of PC61BM and a newly designed non-fullerene electron transport material SFX-PDI2. The formed binary system primely implements in the form of a thin, uniform and full coverage ETL, and possesses more excellent electron extraction and transport properties than both pristine PC61BM and pristine SFX-PDI2. As a result, the binary ETL based PSC with CsPbI2Br as light harvesting material achieved an efficiency as high as 15.12%, which is among the highest performance for inverted planar structured all-inorganic PSC.