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

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.

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