Molecular lead halide perovskite layer bridged AgBiS₂ nanocrystals for efficient thin film solar cells.

Abstract

Ternary chalcogenide AgBiS₂ nanocrystals have emerged as an environmentally friendly and stable material for ultra-thin film lightweight low-cost solar cells. However, their development is currently limited by the poor charge transport characteristics, mainly due to low carrier mobility and the prevalence of surface defects. This leads to a short carrier diffusion length, which severely restricts the thickness of the photoactive layer and the absorption of near-infrared photons. Here, we demonstrate ligand-mediated heteroepitaxial growth of a molecular lead halide perovskite layer bridges along the (100) facet of AgBiS₂ nanocrystals, facilitating both efficient surface passivation and charge transport. The bridged nanocrystals enable the annealing process at elevated temperatures without inducing defect formation. This results in a greater cationic disorder, fully activating their light-absorption capability. The synergistic effect of structural modulation and cation disorder engineering addresses the long-standing trade-off between charge extraction and light absorption of AgBiS₂ nanocrystal solar cells, enabling thick-film fabrication to compensate for losses in infrared absorption. Consequently, the resultant solar cells with a 185 nm-thick AgBiS₂ nanocrystal layer achieve a certified power conversion efficiency of 11.22% and a short-circuit current of ~ 34 mA cm^-2 under AM 1.5 G illumination (aperture area: 0.022 cm²), representing a record-high performance.