Manipulating Buried Interface via Aromatic Amino Acid Derivatives for Wide‐Bandgap Perovskite Solar Cells and Tandem Devices

ABSTRACT All‐perovskite tandem solar cells (TSCs) constructed by wide‐bandgap (WBG) and narrow‐bandgap (NBG) perovskites represent promising future to exceed the Shockley‐Queisser limit due to the differential absorption of spectrum. However, the WBG perovskite sub cell suffers from substantial open‐circuit voltage ( V _OC ) losses and poor photovoltage performance caused by the severe phase segregation in the bulk, high defects density and non‐radiative recombination losses at the buried interface. Herein, this work introduces a buried interfacial engineering by inserting N‐Benzoyl‐(2R,3S)‐3‐phenylisoserine (NBP) molecule between [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl) butyl] phosphonic acid (Me‐4PACz) and WBG perovskite layer, which simultaneously enhances film quality and energy level alignment. Additionally, experimental investigations demonstrate that the C═O and N─H groups in NBP exhibit significant effects in fixing uncoordinated Pb ²⁺ ions and passivating iodide vacancies, suppresses halide phase segregation and reduces defect state density at the buried interface. Eventually, NBP‐modified WBG PSCs achieved a power conversion efficiency (PCE) of 20.81% with V _OC of 1.371 V. Notably, the device exhibited exceptional photostability, retaining 85.3% of its initial PCE after 1000 h of maximum power point tracking (MPPT). Moreover, integrating the NBP‐modified WBG sub cell with 1.25 eV NBG sub cell obtains a two‐terminal (2T) TSCs with an impressive PCE of 29.05%.