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-9H-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 CuInGaSe₂ (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.