Efficient interfacial optimization of NiOx-based perovskite solar cells via a butterfly-structured semiconductor

Abstract

Suppressed efficiency and weak device stability are two critical issues for NiO_x-based inverted perovskite solar cells due to the mismatched energy level alignment, weak passivation to the perovskite, and perovskite degradation induced by detrimental Ni^>3+ species on the surface of NiO_x. Herein, a novel organic semiconductor (Y34) possessing a butterfly-like structure is designed and synthesized by incorporating four 4,4′-dimethoxytriphenylamine electron-donors with a π-conjugated dithieno[3,2-a:2′,3′-c]phenazine electron-acceptor. The synergistic effect of this donor–acceptor electron feature and the highly planar molecular conjugation contributed to high hole mobility and a well-matched energy level with MAPbI₃-based perovskite. When employed as an interfacial layer between the perovskite and NiO_x, the N, S, and O heteroatoms in Y34 effectively improved the quality of perovskite film and further suppressed the defects-assisted non-radiative recombination. Furthermore, the Y34-constructed interlayer decreased the concentration of harmful Ni^>3+ species on the NiO_x surface. Consequently, the device with Y34-modified NiO_x exhibited a maximum efficiency of 18.79% with impressive long-term stability. It retained 76% of the initial efficiency after 90 days of one-sun irradiation in a N₂ environment. This study suggested that Y34 holds great promise in addressing the challenging issues that hinder the improvement of the performance of NiO_x-based perovskite solar cells.