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 V-oc and PCE (power conversion efficiency). When CH3NH3PbI3 is used as the light absorber, the cell with PEDOT:PSS HTL gives a V-oc of 0.96 V and a PCE of 12.35%, while the cell with m-PEDOT:PSS layer gives a V-oc of 1.11 V and a PCE of 15.56%. Enhanced V-oc 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 V-oc of 1.52 V.