Efficient perovskite light-emitting diodes achieved by suppressing the acidic surface of PEDOT:PSS films

Interfaces between functional layers are among the most crucial and intricate structures in electronic devices with a multilayer structure; they determine the injection and distribution of charge carriers, as well as the efficiency and stability of the devices. Here, a general but previously overlooked acidic surface of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films is investigated in detail to construct efficient perovskite light-emitting diodes. This potent acidity leads to the decomposition of perovskites by the diffusion of active protons coming from the PSSH components in PEDOT:PSS. A polyethylenimine ethoxylated (PEIE) modifying layer is used to neutralize the PSSH on the surface of PEDOT:PSS films, which not only protects the perovskites, but also enhances device efficiency greatly. A peak current efficiency of 56.7 cd/A is obtained, enhancing by about 7 times compared with the control device without PEIE (7.8 cd/A). Our work addresses a long-standing but seldom-discussed issue in perovskite light-emitting diodes—the strong dependence of device performance on the surface characteristics of PEDOT:PSS films.