Nickel phthalocyanine as an excellent hole-transport material in inverted planar perovskite solar cells.

Pristine nickel phthalocyanine (NiPc) was introduced as a hole transporting material (HTM) in inverted planar perovskite solar cells (PSCs) for the first time. A power conversion efficiency of 14.3% was achieved, outperforming the values obtained in the solar cells based on the CuPc HTM, which is a typical representative of metal phthalocyanine based HTMs. Moreover, inverted planar PSCs based on NiPc HTMs show a very weak hysteresis behavior.