PEDOT:PSS‐Metal Oxide Composite Electrode with Regulated Wettability and Work Function for High‐Performance Inverted Perovskite Solar Cells

Abstract Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) can be roll‐to‐roll deposited on the substrate facilely in the electronics, but its acidity and mismatched energy level limit the performance and stability. Herein, different metal salts are incorporated into PEDOT:PSS solution to prepare PEDOT:PSS‐A_xO_y (metal oxide) composite hole transport layer and it is found that the performance of inverted perovskite solar cells (PSCs) can be greatly enhanced. PSC using PEDOT:PSS‐MoO_x has achieved much higher power conversion efficiency (PCE) (19.64%) than that of pristine PEDOT:PSS (12.19%). Two key factors are important for the performance enhancement. First, the increased surface free energy of PEDOT:PSS‐A_xO_y is beneficial for the formation of large crystal size and pinhole‐free film, leading to reduced nonradiative recombination. Second, the work function of PEDOT:PSS can be tuned to match the energy level of photoactive layer with small amount incorporation, which greatly enhances the photovoltage by a factor of 1.1. Besides, the devices based on PEDOT:PSS‐A_xO_y exhibit improved long‐term stability. Unencapsulated PSCs with PEDOT:PSS‐MoO_x retain over 90% and 80% of their initial PCEs in N₂ for 45 d and in ambient air for 20 d, respectively. The modified PEDOT:PSS solutions overcome the intrinsic imperfection and can be potentially employed for large‐scale production in the electronic devices.