Polymer-assisted synthesis of mixed-halide quasi-2D perovskites for tunable blue-green lasers†

Abstract

Blue-green lasers are vital for optical communication, display technology, and biological imaging. Metal halide perovskites are promising gain media, owing to their exceptional optoelectronic properties. While single-halide perovskites excel in green, red, and near-infrared lasing, mixed chloride–bromide variants for blue-green wavelengths face challenges in precise halide control and phase stability. Quasi-2D perovskites, with enhanced stability and tunability, leverage their quantum well (QW) structure for efficient energy transfer, showing promise for blue lasing. Here, we report a polymer-assisted synthesis using polyvinyl pyrrolidone (PVP) to fabricate chloride–bromide mixed quasi-2D perovskites with superior lasing performance. PVP suppresses phase separation, enabling precise wavelength tuning of low-threshold blue-green lasing and favoring high-n QW species for efficient energy transfer. The resulting thin films exhibit amplified spontaneous emission (ASE) with thresholds as low as 17.12 ± 0.61 μJ cm⁻² and tunable ASE wavelengths from 477 to 510 nm, linearly dependent on the chloride-to-bromide ratio. PVP also enhances processability, enabling micrometer-sized ring arrays as high-quality optical microcavities with lasing thresholds of 14.47 ± 0.57 μJ cm⁻². This scalable approach maintains thresholds below 38 μJ cm⁻² across compositions, offering a cost-effective, stable platform for blue-green lasers with wide-ranging applications.