Enhanced electron transport induced by a ferroelectric field in efficient halide perovskite solar cells

Perovskite solar cells have been appearing as a superior photovoltaic device owing to their high photovoltaic performance and low cost of fabrication. The formation of a compact and uniform perovskite layer with large crystal size is a significant factor to get the best device performance. In this work, polyvinylidene difluoride (PVDF) was used as a ferroelectric polymer additive to fabricate high-performance mesoporous CH3NH3PbI3-xClx mixed-halide perovskite solar cells in a sequential deposition method. Power conversion efficiency has been enhanced from 10.4 to 16.51% in an ambient atmosphere in the presence of an optimized amount of PVDF assuring continuous and smooth layers with large grain size. Besides morphological improvements, this progress in the photovoltaic performance is attributed to the dipole field exerted by PVDF that leads to enhanced charge separation. Further improvements in efficiency (18.60%) have been achieved by directing the dipoles under an external field.