Lead-Free, Blue Emitting Bismuth Halide Perovskite Quantum Dots

Lead halide perovskite quantum dots (QDs) are promising candidates for future lighting applications, due to their high quantum yield, narrow full width at half maximum (FWHM), and wide color gamut. However, the toxicity of lead represents a potential obstacle to their utilization. Although tin(II) has been used to replace lead in films and QDs, the high intrinsic defect density and oxidation vulnerability typically leads to unsatisfactory material properties. Bismuth, with much lower toxicity than lead, is promising to constitute lead-free perovskite materials because Bi³⁺ is isoelectronic to Pb²⁺ and more stable than Sn²⁺ . Herein we report, for the first time, the synthesis and optical characterization of MA₃ Bi₂ Br₉ perovskite QDs with photoluminescence quantum yield (PLQY) up to 12 %, which is much higher than Sn-based perovskite nanocrystals. Furthermore, the photoluminescence (PL) peaks of MA₃ Bi₂ X₉ QDs could be easily tuned from 360 to 540 nm through anion exchange.