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 –C═O 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.