Tuning Surface Wettability of Buffer Layers by Incorporating Polyethylene Glycols for Enhanced Performance of Perovskite Solar Cells
Zhiyong Liu, Pengfei Liu, Tingwei He, Leilei Zhao, Xilin Zhang, Jien Yang, Haigang Yang, Hairui Liu, Ruiping Qin, Mingjian Yuan
Abstract
Phenyl-C61-butyric acid methyl ester (PCBM) has been widely researched as a passivate electron transport layer in planar n-i-p-type perovskite solar cells (PSCs). However, due to the terrible wettability of PCBM, the growth of perfect large-area perovskite films on the electron transport layer treated by PCBM is a huge challenge, which limits the commercial application of PSCs. Herein, we incorporate a hydrophilic polymer polyethylene glycol (PEG) into PCBM to ameliorate its wettability. A high-quality perovskite film can be prepared on a 2 × 2 cm substrate. Hydrogen-bonding effects between the PEG-PCBM buffer layer and the perovskite layer can further stabilize the electron transport layer/perovskite interface. Based on the improved electron transport and suppressed carrier recombination, a device with an active area of 1.03 cm2 achieves an efficiency of 18.25%. In addition, the first-principles calculations indicate that PEG has stronger adsorption (Eads = −0.37) toward H2O than the MAPbI3 perovskite (Eads = −0.25), which can prevent water molecules from infiltrating the perovskite. The unsealed device still maintains 90% of the initial efficiency under ambient conditions, with 30–40% relative humidity for 22 days. These outstanding properties are attributed to the unique molecular structure and prominent wettability of PEG.