Reducing the cell-to-module performance gap of inorganic perovskites using anisotropically structured hole transport materials

Abstract

All inorganic perovskites have emerged as attractive light-harvesting materials for perovskite solar cells due to their superior thermal and photostability. However, the significant performance gap between lab-scale cells and large-area modules remains a major challenge for commercialization. Here, we introduced an anisotropically engineered hole transport material, 2′,7′-bis(3,6-dimethoxy-9H-carbazol-9-yl)-N2,N2,N7,N7-tetrakis(4-methoxyphenyl)-9,9′-spirobi[fluorene]-2,7-diamine (SF-MPA-MCz), which exhibited stronger interfacial adsorption and improved energy-level alignment with CsPbI₃ and formed a uniform and robust hole transport layer, which enhanced both efficiency and stability. As a result, CsPbI₃-based devices achieved power conversion efficiencies (PCE) of 20.0% in 0.16 cm² single cells and 16.7% in 186 cm² modules, representing the narrowest cell-to-module PCE gap reported for inorganic PSCs. Moreover, the enhanced interfacial coupling between SF-MPA-MCz and CsPbI₃ effectively suppressed thermal degradation and ion migration, thereby improving device durability. The encapsulated module maintained 80% of its initial PCE after 1500 h of damp-heat testing (i.e., at 85 °C and in 85% R. H. air) and retained 80% of its initial PCE after 4000 h of operation under continuous 1-sun illumination at 40 °C.