Robust Full-Spectrum-Responsive Multi-junction Tandem Solar Cells via Enhanced Near-Infrared Photon Harvesting

Developing robust multi-junction tandem photovoltaics remains constrained by the instability of mixed-halide perovskite subcells, given their dominating contribution to overall power output. Integrating near-infrared (NIR) PbS quantum dots (QDs) with FAPbBr3 and crystalline silicon (c-Si) broadens spectrum utilization while improving overall operational stability by reducing the perovskite power contribution. However, enlarged (100) facets and the trade-off between film thickness and quality limit efficient NIR photon harvesting. Herein, a Lewis-basic dihydrazide molecule achieves universal passivation across diverse PbS QD facets via synergistic lead chelation and hydrogen-bonding interactions. Consequently, 0.8 eV PbS QD solar cells with a 685 nm-thick active layer achieve a short-circuit current density of 41.31 mA cm–2 and a 1100-nm-filtered efficiency of 1.80%. The resulting FAPbBr3/c-Si/PbS triple-junction tandems achieve a promising efficiency of 31.04%, with the perovskite subcell contributing 30.4% of the total power output, demonstrating a well-matched operational lifetime. This work offers a strategic framework for efficient multi-junction tandem photovoltaics.