Hydrogen-iodide bonding between glycine and perovskite greatly improve moisture stability for binary PSCs

Abstract

In recent years, the maximum power conversion efficiency (PCE) of perovskite solar cells (PSCs) has exceeded 25%. However, stability, especially under high relative humidity, has become a great obstacle for commercialization of perovskite devices due to its intrinsic defects. Interface modification is an effective method to improve the performance of PSCs for it could validly restrain defects and prevent decomposition of perovskite. In this paper, interface properties have been greatly improved by glycine (GLY) doped SnO 2 electron transport layer (ETL) in planar binary PSCs. SnO 2 -GLY ETL leads to improved band alignment, reduced charge recombination and enhanced electron mobility. XPS and NMR results demonstrate that the ammonia group in GLY combined with perovskite through hydrogen-iodide bonding, which greatly improves the moisture stability of the devices. The best PCE of the perovskite solar cell increased from 19.08% to 21.18%, and GLY modified devices can maintain 88% of its initial PCE after 7 days under 60 ± 5% relative humidity (RH) in ambient condition without any encapsulation. While, thermal stability test results indicating that hydrogen bonding is just a little helpful for improving stability at high temperature. This work indicates that forming hydrogen bonding between perovskite and ETL is an effective way to enhance moisture stability for commercialization of PSCs. • Interface properties between SnO 2 ETL and PSCs are improved by glycine (GLY), leading to enhanced PCE from 19.11% to 21.18%. • The amino group in GLY is bound to perovskite by hydrogen iodide bond, which greatly improves water stability of the device. • Long-term and thermal stability of the devices have also been improved.