Bifunctional Passivation of Wide-Bandgap Perovskite Solar Cells via Long-Chain Organic Ammonium Salts

Perovskite solar cells (PSCs) with wide bandgaps (WBG) have emerged as critical enablers as the top subcells in various series-connected configurations, enabling effective absorption of high-energy photons and yielding a high open-circuit voltage (<i>V</i>_OC). However, these cells face significant challenges, including substantial photovoltage losses and phase separation, which hinder their potential efficiency and stability. We develop a molecular additive strategy employing the bifunctional ODABr diammonium salt (octadecane-1,8-diammonium bromide) during perovskite processing, and a hierarchically structured two-dimensional/three-dimensional (2D/3D) perovskite film with preferred crystallographic alignment and enhanced phase homogeneity is successfully engineered. The introduction of ODABr not only promotes preferential orientation growth of the perovskite film along the (100) crystal plane, enhancing charge carrier mobility, but also achieves higher phase stability (AM 1.5G). This dual functionality significantly reduces nonradiative recombination losses and prolongs carrier lifetime, thereby achieving a V_OC of 1.22 V and a power conversion efficiency (PCE) of 20.71%. This research provides an important material strategy for realizing highly efficient and stable WBG perovskite solar cells.