Synergistic Molecular Stacking in an Asymmetric Self-Assembled Bilayer for Universally Elevating the Performance of...

Perovskite photovoltaics have demonstrated remarkable progress in power conversion efficiency, showing great potential for broad applications. However, interfacial issues such as energy-level mismatch and defect density remain key challenges that limit device performance. To address the rigid energy levels and inhomogeneous coverage of conventional symmetric self-assembled monolayers (SAMs), we present an asymmetric self-assembled bilayer strategy. In this design, a bottom CbzBF SAM is anchored to the ITO substrate to optimize energy-level alignment for hole extraction, while a top CbzBT SAM simultaneously passivates interfacial defects and modulates perovskite crystallization. As a result, single-junction perovskite photovoltaics (PPVs) with a bandgap of 1.68 eV attain power conversion efficiency (PCE) of 22.86% with a high fill factor (FF) of 86.54% under standard AM1.5G illumination, along with 43.88% PCE under 1000 lx indoor LED lighting. Critically, the CbzBF/CbzBT bilayer enabled fill factors over 85% in PPVs with bandgaps of 1.65, 1.72, and 1.75 eV, ranking among the highest reported values and underscoring its exceptional universality. Moreover, our two-terminal perovskite/silicon tandem solar cells reached a PCE of 30.69%. This study presents a practical and effective interfacial design strategy toward high-performance perovskite photovoltaics.