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 1,4-benzenebisphosphonic 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 Pb²⁺, 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 × 10¹⁵ to 2.90 × 10¹⁵ cm⁻³ and carrier lifetimes extended from 794.2 ns to 1762 ns. Unencapsulated cells retain over 92% of their initial efficiency after 1973 h under nitrogen, underscoring the efficacy of BBA-mediated buried-interface passivation for both performance and stability in WBG perovskite solar cells.