Contact Potential Homogenization via Buried Interface Engineering Enables High‐Performance Wide‐Bandgap Perovskite Photovoltaics

Abstract Microscale imperfections and inhomogeneity at buried interface leads to energy losses and insufficient carrier extraction of wide bandgap (WBG) perovskite solar cells (PSCs). Here, we report a collaborative buried interface strategy by introducing 3‐aminopropanoic acid (3‐APA) to mix with [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) as hole‐selective self‐assembled monolayer (SAM). With the addition of 3‐APA, the wettability of perovskite precursors is increased. Furthermore, the film morphology and heterogeneity at perovskite buried interface is improved. As a result, the nonradiative recombination and interfacial energy loss are greatly suppressed. This strategy also leads to marginally higher ionization potential of hole‐selective monolayers, approximating to the valence band of perovskite film. Benefits from suppressed charge transfer loss and nonradiative recombination loss, the mixed SAM strategy is present to overcome the passivation transport trade‐off, delivering V_OC × FF of 84.5% of the S–Q limit. The combine benefits enable efficient 1.67 eV WBG PSCs with a power conversion efficiency of 22.4% and a high open circuit voltage of 1.255 V and fill factor of 85.5%. Under mix SAM strategy, we also demonstrat all‐perovskite tandem solar cells with efficiency of 28.4%.