Colloidal 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 (N_g)≈ 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.

胶体半导体量子阱已经成为可用于溶液加工激光器的有前途的材料平台。然而，由于其光增益的应用具有II-VI族半导体纳米晶体中光放大的多激子特性，因此会遭受非辐射俄歇衰变。在这里，我们显示了在特殊设计的CdSe / CdS @ CdZnS核/ crown @梯度合金壳量子阱中光增益阈值的亚单激子水平。阻碍俄歇复合的亚单激子整体平均增益阈值（N _g）≈0.84（每个粒子），加上量子阱的大吸收截面，使我们能够观察到从〜800 nJ cm ^-2的超低泵注量在所有胶体纳米晶体中，至少比以前报道的值高三倍。最后，使用这些梯度带壳量子阱，我们证明了垂直腔表面发射激光器在7.5μJcm ^-2的低激光阈值下工作。这些结果代表了实现可溶液处理的电动胶体激光器的重要一步。