Efficient and thermally stable inverted perovskite solar cells by introduction of non-fullerene electron transporting materials

Abstract

Highly efficient and thermally stable inverted CH₃NH₃PbI₃ (MAPbI₃) and HC(NH₂)₂PbI_3−xBr_x (FAPbI_3−xBr_x) perovskite planar solar cells are demonstrated by using a N,N′-bis(phenylmethyl)naphthalene-1,4,5,8-tetracarboxylic diimide (NDI-PM)-based electron transporting material (ETM) instead of a conventional fullerene-based phenyl-C₆₁-butyric acid methyl ester (PCBM) ETM. The MAPbI₃ and FAPbI_3−xBr_x devices with the NDI-PM-based ETM exhibit 18.4% and 19.6% power conversion efficiency under an illumination of 1 Sun (100 mW cm⁻²), respectively, which are comparable to the efficiency of PCBM ETM-based ones (18.9% and 20.0%). The improved thermal stability of NDI-based perovskite solar cells is attributed to much stronger hydrogen bonds in the NDI-PM molecular crystals than the PCBM crystals.