Buried Interface Regulation with a Supramolecular Assembled Template Enables High‐Performance Perovskite Solar Cells for Minimizing the VOC Deficit

Despite the rapid development of perovskite solar cells (PSCs) in the past decade, the open-circuit voltage (V_OC) of PSCs still lags behind the theoretical Shockley-Queisser limit. Energy-level mismatch and unwanted nonradiative recombination at key interfaces are the main factors detrimental to V_OC. Herein, a perovskite crystallization-driven template is constructed at the SnO₂/perovskite buried interface through a self-assembled amphiphilic phosphonate derivative. The highly oriented supramolecular template grows from an evolutionary selection growth via solid-solid phase transition. This strategy induces perovskite crystallization into a highly preferred (100) orientation toward out-of-plane direction and facilitated carrier extraction and transfer due to the elimination of energy barrier. This self-assembly process positively passivates the intrinsic surface defects at the SnO₂/perovskite interface through the functionalized moieties, a marked contrast to the passive effect achieved via incidental contacts in conventional passivation methods. As a result, PSCs with buried interface modification exhibit a promising PCE of 25.34%, with a maximum V_OC of 1.23 V, corresponding to a mere 0.306 V deficit (for perovskite bandgap of 1.536 eV), reaching 97.2% of the theoretical V_OC limit. This strategy spontaneously improves the long-term operational stability of PSCs under thermal and moisture stress (ISOS-L-3: MPP, 65 °C, 50% RH, T₉₂ lifetime exceeding 1200 h).