Dual-Channel Sensibilization of Bi3+ Boosts Near-Unity Photoluminescence Quantum Yield Rare-Earth-Free Halide Perovskite for Energy-Saving Agricultural Cultivation Film

The development of low-cost, rare-earth-free light conversion materials is critical for sustainable agriculture. Herein, we report a Bi 3+ /Mn 2+ co-doped lead-free double perovskite Cs 2 Ag 0.8 Na 0.2 InCl 6 synthesized via an environmentally friendly mechanochemical method. The phosphor exhibits a broad-spectrum emission (400–800 nm) with a full width at half maximum (FWHM) of 206 nm, attributed to the synergistic effect of Bi 3+ -activated self-trapped excitons (STEs) and Mn 2+ 4 T 1 → 6 A 1 transitions. Bi 3+ doping not only extends the absorption range to the UVA region (350–400 nm) but also enhances the photoluminescence quantum yield (PLQY) to 99.3% through Bi 3+ →STE and Bi 3+ →Mn 2+ energy transfer. A sunlight conversion film fabricated by incorporating the phosphor into Ecoflex-0031 silica gel shows excellent mechanical stability (tensile elongation retained over 16 days) and environmental durability. Plant growth experiments with chives and hydrocotyle vulgaris demonstrate significant improvements under the film: chive stem length increased by 136%, hydrocotyle leaf width by 37%, and fresh weight by 17%. This work highlights the potential of Bi 3+ /Mn 2+ co-doped perovskites as efficient, low-cost light conversion agents for energy-saving agricultural cultivation film.