Albendazole Passivation in Inverted Wide‐Bandgap Perovskite Solar Cells toward Efficient Perovskite/CuInGaSe2 Tandem Photovoltaics

Abstract Self‐assembled materials (SAMs) like [4‐(3,6‐dimethyl‐9 H ‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) are commonly used as hole transport layers (HTLs) in inverted wide‐bandgap (WBG) perovskite solar cells. However, the poor wettability of perovskite precursor solutions on Me‐4PACz and its polarity‐induced aggregation hinder high‐quality film formation. To address these challenges, albendazole (ALB) is introduced as a surface modifier for Me‐4PACz. The ALB solution mitigates the aggregation of Me‐4PACz and promotes the desorption and rearrangement process of weakly bound Me‐4PACz molecules. Concurrently, its Lewis basic moiety improves film quality, reduces buried interfacial defects, and optimizes energy level alignment. Additionally, ALB forms directional π–π interactions with Me‐4PACz, ultimately suppressing non‐radiative recombination and facilitating charge carrier transport. As a result, ALB‐optimized inverted WBG perovskite solar cells achieve a power conversion efficiency (PCE) of 22.68%, with unencapsulated devices retaining 93.87% of their initial efficiency after 736 h of continuous maximum power point tracking (MPPT) under illumination. Furthermore, integrating the ALB‐modified semi‐transparent perovskite top cell with a 1.03 eV bandgap CuInGaSe 2 (CIGS) bottom cell yields a four‐terminal tandem device with an impressive total efficiency of 29.06%. This dual‐objective strategy provides a simple and effective method for simultaneously improving the film quality of both the HTL and the perovskite layer.