Molecular Bridge Overcomes Carrier Transport Limitations for High-Efficiency Quantum Dot Photovoltaic

Metal halide perovskite quantum dots (QDs) are promising candidates for next-generation photovoltaic devices; however, their practical performance is largely limited by inefficient charge transport between neighboring QDs. To address this issue, we designed and synthesized a series of conjugated functional molecules, Mono-OMe, Bi-OMe, and Tetra-OMe, featuring varying numbers of anchoring sites to tailor the interfaces within solid QD films. The π-conjugated backbone promotes efficient charge transport between QDs, while multidentate anchoring groups enhance QD surface passivation. Systematic experimental characterizations reveal that higher denticity leads to more effective enhancements of the QD/organic heterointerfaces. In particular, the rationally designed tetradentate molecular bridge Tetra-OMe forms more robust coordination with perovskite QDs, effectively passivating surface defects and promoting charge transport between adjacent QDs. As a result, molecularly bridged QD-based solar cells achieve high-power conversion efficiencies (PCEs) of 17.71% for wide-bandgap CsPbI₃ and 19.06% (certified 18.72%) for narrow-bandgap FAPbI₃ perovskite QDs, representing state-of-the-art performance in QD photovoltaics.