Nickel Cobaltite Nanosheet Layer as Hole‐Transporting Material in Inverted Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) were demonstrated as prospective candidates to traditional solar cells due to their low‐cost, easy fabrication and excellent opto‐electronic properties. In this study, a quality p‐type semiconductor nickel cobaltite (NiCo 2 O 4 ) nanosheet layer was prepared on fluorine‐doped tin oxide (FTO) substrate via a simple solution thermal method, which was applied as hole‐transporting materials (HTMs) in typical inverted PSCs. The perovskite layer was synthesized by a fast‐crystallization method to form a full coverage film on NiCo 2 O 4 nanosheet layer, which can avoid short circuit of contacting PCBM with NiCo 2 O 4 , increase the carrier transportation at the interface and hence lead to less recombination process. Fine crystalline perovskite on NiCo 2 O 4 have a fast hole‐extraction, leading to a champion efficiency of 18.6 % without hysteresis, which indicates the possible replacement of organic HTMs to fabricate low‐cost and highly stable PSCs.