Modified PEDOT Layer Makes a 1.52 V Voc for Perovskite/PCBM Solar Cells

The work functions for charge transport layers in perovskite solar cells affect device performance significantly. In this work, the regular poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is modified by adding a polymer electrolyte PSS‐Na to improve its HTL function in perovskite solar cells. The modified PEDOT:PSS films (called m‐PEDOT:PSS) possess higher work function than the regular one. Its energy level matches the valence band of perovskite very well, leading to enhanced Voc and PCE (power conversion efficiency). When CH3NH3PbI3 is used as the light absorber, the cell with PEDOT:PSS HTL gives a Voc of 0.96 V and a PCE of 12.35%, while the cell with m‐PEDOT:PSS layer gives a Voc of 1.11 V and a PCE of 15.56%. Enhanced Voc and PCE are also achieved when CH3NH3PbI2Br or CH3NH3PbBr3 is used as the light absorber. The m‐PEDOT:PSS/CH3NH3PbBr3/PC61BM solar cells demonstrate an outstanding Voc of 1.52 V.