Regulate defects and energy levels for perovskite solar cells by co-modification strategy

The under-coordinated bonds and deep-level defects on the perovskite surface always act as non-radiative recombination centers and lead to energy loss . The usual surface modification efficiency is limited because of the diversity of surface terminals and defects. Here, a co-modification strategy is proposed for more-thorough modification by reconstructing and post-modifying perovskite surface defects . In detail, the tetrahydrofuran (THF) is firstly implemented to remove the organic component and expose the perovskite surface with uniform Pb terminals and defects, and then the 4-Methylbenzyl Mercaptan (MBM) is used to form strong R-S-Pb bonding with them, which achieves the increase and decrease of under-coordinated Pb donor defects. Correspondingly, the surface energy level of perovskite is observed a consistent change with defects. THF/MBM co-modification changes the perovskite surface energy level from n-type toward p-type, which enhances the holes’ transport efficiency. As a result, the best power conversion efficiency (PCE) increases from 22.23% of the control device to 24.17% of the device with THF/MBM co-modification. Notably, a full-coverage and strong-bonding protective layer is formed by THF/MBM co-modification, which facilitates excellent device stability (Retains 93.7%, after 3360 h in N 2 ). This strategy shows great potential in high-performance PSCs by reconstructing defects and energy level of perovskite surface.