Haonan Sun, Guibin Shen, Huei Min Chua, Darrell Jun Jie Tay, Yuanjie Su, Yahong Pu, Yanju Wang, Yeow Boon Tay, Hongkang Fu, Subodh G. Mhaisalkar, Shixuan Du, Nripan Mathews, Wei Lin Leong
Buried interface quality in p-i-n perovskite solar cells (PSCs) is shown to improve via the use of a mixed self-assembled monolayer (SAM) of [4-(3,6-dimethyl-9 H -carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) and (9H,9′H-[3,3′-bicarbazole]-9,9′-diylbis(butane-4,1-diyl))diphosphonic acid (Bi4PACz), eschewing the need for a NiO x layer. The bisphosphonic acid-based Bi4PACz minimizes SAM aggregation and enhances the wettability and uniformity. It also coordinates with the perovskite, passivating defects and suppressing PbI 2 aggregation, thereby minimizing recombination losses. The improved buried interface quality leads to power conversion efficiencies (PCEs) of 24.48%, 25.65%, and 22.60% for triple cation PSCs with bandgaps of 1.61, 1.58, and 1.68 eV, respectively, demonstrating the wide applicability of this approach. Under temperature conditions, the PSCs retained 84% of initial PCE after 1200 h at 85 °C and 97% after 250 thermal cycles (−40 to +70 °C), indicating its potential for space-related applications. This mixed-SAM approach establishes a universal pathway toward efficient and temperature-stable perovskite photovoltaics.