High-efficiency narrow-band blue emission from lead-doped Cs2ZnBr4 nanocrystals

Abstract

All-inorganic metal halide nanocrystals (NCs) with high-efficiency narrow-band photoluminescence (PL) are highly desirable for display applications. Herein, we report a strategy to achieve efficient narrow-band blue PL in 0D Cs2ZnBr4 NCs via minor Pb2+ doping. Upon doping with 0.1 mol% Pb2+, the intrinsically non-luminescent Cs2ZnBr4 NCs become efficiently luminescent, with a sharp emission peak at 433 nm (full-width at half maximum of ≈10.2 nm) and a high quantum yield of 82.9 %. With the aid of the first-principles calculations, we unveil that the narrow-band blue PL originates from the localized exciton emission arising from the peculiar electronic band structure induced by Pb2+ doping, in which the photogenerated excitons in [PbBr4]2− tetrahedra are trapped and localized within [ZnBr4]2− tetrahedra. Furthermore, by control of the Pb2+ concentration (0.1–3.0 mol%), we achieve dual-band-tunable blue/green PL in Cs2ZnBr4: Pb2+/CsPbBr3 hybrid NCs with high efficiency and signifcantly improved stability compared to that of bare CsPbBr3. These findings provide a unique approach to achieve highly efficient narrow-band PL in metal halide NCs via minor Pb2+ doping, which largely mitigates the toxicity concern about lead halide perovskites and thus may open up new opportunities for the materials design and device engineering in practical applications.