Taghipour, NimaDelikanlı, SavaşShendre, S.Sak, MustafaLi, M.Işık, FurkanTanrıöver, İbrahimGüzeltürk, B.Sum, T. C.Demir, Hilmi Volkan2021-03-012021-03-0120202041-1723http://hdl.handle.net/11693/75684Colloidal semiconductor quantum wells have emerged as a promising material platform for use in solution-processable lasers. However, applications relying on their optical gain suffer from nonradiative Auger decay due to multi-excitonic nature of light amplification in II-VI semiconductor nanocrystals. Here, we show sub-single exciton level of optical gain threshold in specially engineered CdSe/CdS@CdZnS core/crown@gradient-alloyed shell quantum wells. This sub-single exciton ensemble-averaged gain threshold of (Ng)≈ 0.84 (per particle) resulting from impeded Auger recombination, along with a large absorption cross-section of quantum wells, enables us to observe the amplified spontaneous emission starting at an ultralow pump fluence of ~ 800 nJ cm−2, at least three-folds better than previously reported values among all colloidal nanocrystals. Finally, using these gradient shelled quantum wells, we demonstrate a vertical cavity surface-emitting laser operating at a low lasing threshold of 7.5 μJ cm−2. These results represent a significant step towards the realization of solution-processable electrically-driven colloidal lasers.EnglishColloidal semiconductor quantum wellsSub-single exciton optical gain thresholdGradient alloy shellingArticle10.1038/s41467-020-17032-8