Molecular engineering of PEDOT:PSS for enhancing open-circuit voltage in organic/silicon heterojunction solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/silicon (Si) heterojunction solar cells (HSCs) have garnered extensive interest owing to their potential for high efficiency and low cost. However, their performance is constrained by a limited open-circuit voltage (VOC). In this manuscript, PEDOT:PSS films endowed with both high conductance and high work function via an alcohol-doping-based molecular engineering strategy were applied to induce strong inversion layers on the n-Si surface and generate large built-in voltage in HSCs. This molecular engineering strategy enables precise modulation of PEDOT:PSS molecular building blocks, achieving a work function tuning range from 4.81 to 4.93 eV while retaining high conductivity exceeding 650 S/cm. A photovoltaic device with alcohol-doped PEDOT:PSS delivers a large VOC of 0.66 V without additional modifications and a power conversion efficiency of 12.80%. This study on the molecular engineering of PEDOT:PSS establishes an effective and simplified pathway for fabricating PEDOT:PSS/Si HSCs with high VOC.