Bisphosphate Group Molecules Contribute to the Performance of Wide-Bandgap Perovskite Solar Cells

Abstract

Developing high-quality wide-bandgap perovskites is essential for efficient silicon/perovskite tandem photovoltaics, yet large open-circuit voltage (V oc ) deficits and limited operational stability remain critical bottlenecks. In this work, we introduce 1,4benzenebisphosphonic acid (BBA) as a buried-interface passivation agent between the NiO x /Me-4PACz hole-transport layer and the perovskite absorber, whose bis-phosphonic acid groups coordinate with Pb 2+ , I -, and FA + to passivate defects, suppress non-radiative recombination, inhibit ion migration, and reduce interface trap formation. The optimized 1.66 eV band-gap devices deliver a state-of-the-art V oc of 1.195 V (0.455 V deficit) and a stabilized power conversion efficiency of 21.79 %, with trap densities reduced from 3.37×10 15 to 2.90×10 15 cm -3 and carrier lifetimes extended from 794.2 ns to 1762 ns. Unencapsulated cells retain over 92 % of their initial efficiency after 1,973 h under nitrogen, underscoring the efficacy of BBA-mediated buried-interface passivation for both performance and stability in WBG perovskite solar cells.