Boosted Ultraviolet Irradiation and Environmental Stability of Hole Transport Layer-Free Perovskite Solar Cells

Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is 26.1%, their stability is still a roadblock for large-scale commercialization. In the initial density-functional theory research, it is shown that the most damaging type of defect that destroys device performance is undercoordinated Pb2+ on the surface of the perovskite thin film. An ultraviolet-absorbent material, 2-hydroxybenzophenone (HBP), is utilized to specifically passivate this type of defect. In theoretical studies, it is shown that it effectively binds to the undercoordinated Pb2+ via its -CO group. It also passivates I--related defects by forming a hydrogen bond using its -OH group, resulting in decreased trap density and hence prolonged carrier lifetime. The HBP can absorb ultraviolet irradiation, leading to much-reduced UV degradation; its hydrophobic benzene rings protect the perovskite from moisture permeation. As a result, the constructed device reaches a high PCE of 16.39% with superior stability. The bare device maintains 80.4% of its initial PCE after exposure to ambient air for 792 h. In comparison, the control device without HBP retains only 63.2% of its initial efficiency. Under UV irradiation (80 mW cm-2, 365 nm) for 13 h, the former retains 77.9% of its initial PCE while the control device lost 52% of its initial value. Herein, 2-hydroxybenzophenone is introduced into the precursor to passivate the defects and absorb ultraviolet in the perovskite film. Meanwhile, ZnO mesoporous layer is developed as the electron transport layer to improve the effective electron extraction/transport. The power conversion efficiency of the constructed device is up to 16.39%, and the long-term environmental and ultraviolet irradiated stability is also significantly enhanced.image (c) 2023 WILEY-VCH GmbH