Enhanced efficiency and stability of perovskite solar cell by adding polymer mixture in perovskite photoactive layer

Abstract

The key to commercialization of organic‐inorganic lead halide perovskite solar cells (PSCs) is to achieve high photoelectric conversion efficiency (PCE) and long-term stability under ambient condition. In this paper, polymer mixture of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) with appropriate mass ratio are incorporated into PbI2 precursor solution in the preparation process of perovskite film via two-step sequential deposition method in air. The PCE of polymer mixture modified PSC based on ZnO@TiO2 nanorod arrays is better than those of the PSC with single polymer（PVP or PEG）and the pristine one, and the PCE of 1.5 wt%PVP/0.5 wt%PEG modified device increased by 30% compared with that of the unmodified one, which is mainly a consequence of the better quality of perovskite film caused by the synergistic effect including the strong attraction between the C=O in PVP and Pb2+ in perovskite, and the intense hydrogen bond between O atoms from PEG and H atoms in CH3NH3+. Moreover, polymer mixture modified PSC also represents better air stability compared with the device with single polymer or the pristine one，which is largely attributed to the exceptional hygroscopicity of PVP/PEG mixture, the synergistic stabilization of perovskite structure and inhibition of ion migration by the bondings between polymer mixture and perovskite. Furthermore, the mechanism of the interaction between PVP/PEG mixture and CH3NH3PbI3 to increase the efficiency and stability of the PSC was also studied. Our work offers an effective additive to simultaneously improve the efficiency and stability of the PSCs in high humidity environment for further commercial application.