Sub-single exciton optical gain threshold in colloidal semiconductor quantum wells with gradient alloy shelling

• Main Authors: Taghipour, Nima, Delikanli, Savas, Shendre, Sushant, Sak, Mustafa, Li, Mingjie, Isik, Furkan, Tanriover, Ibrahim, Guzelturk, Burak, Sum, Tze Chien, Demir, Hilmi Volkan
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Science; Colloidal Quantum Wells; Lasing
• Online Access: https://hdl.handle.net/10356/144175
• Institution: Nanyang Technological University

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 (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.