Blue Lasing from Heavy-Metal-Free Colloidal Quantum Dots

Colloidal quantum dots (CQDs) have emerged as promising candidates for solution-processed optical gain materials. Despite the substantial progress made with Cd or Pb-contained CQDs, lasing from the environmentally friendly CQDs remains underexplored. Here, the highly emissive ZnSeTe/ZnSe/ZnS and ZnSe/ZnS CQDs is developed. The optical gain and lasing action from such Te-alloyed and intrinsic ZnSe/ZnS CQDs across the blue spectral region is achieved. Te-alloyed ZnSe core manifests a quasitype-II band alignment with the ZnSe intermediate layer, favorable for suppressing the Auger recombination and also lasing wavelength tuning. The transient absorption spectroscopy reveals evidence of a blue optical gain with a threshold of one exciton per dot and a lifetime of 171 ps in the alloyed CQDs. Under a quasicontinuous-wave pumping, lasing is observed from the blue CQDs in Fabry–Pérot cavities with a lower threshold fluence of 12.5 µJ cm⁻² as compared with the traditional counterparts with heavy metals. The demonstration of heavy-metal-free CQD lasing opens up new opportunities in the application of CQDs as efficient and environmental-friendly gain media.