Sub-single exciton optical gain threshold in colloidal semiconductor quantum wells with gradient alloy shelling
Abstract
Colloidal semiconductor quantum wells have emerged as a promising material platform for use in solution-processable light-generation including colloidal lasers. However, application relying on their optical gain suffer from a fundamental complication due to multi-excitonic nature of light amplification in common II-VI semiconductor nanocrystals. This undesirably increases the optical gain threshold and shortens the net gain lifetime because of fast nonradiative Auger decay. Here, we demonstrate sub-single exciton level of optical gain threshold in specially engineered CdSe/CdS@CdZnS core/crown@gradient alloyed shell colloidal quantum wells. This sub-single exciton ensemble-averaged gain threshold of Ng = 0.80 (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 a low pump fluence of 800 nJ cm-2, at least three-folds better than the previously best reported values among all colloidal semiconductor nanocrystals. Moreover, long optical gain lifetimes of 800 ps accompanied with modal gain coefficients of 2,000 cm-1 are achieved. Finally, using these gradient shelled quantum wells, we show a vertical cavity surface-emitting colloidal laser operating at an ultralow lasing threshold of 7.5 micro-joule cm-2. These results represent a significant step towards the realization of solution-processable electrically-driven colloidal lasers.
Cite
@article{arxiv.1906.06913,
title = {Sub-single exciton optical gain threshold in colloidal semiconductor quantum wells with gradient alloy shelling},
author = {Nima Taghipour and Savas Delikanli and Sushant Shendre and Mustafa Sak and Mingjie Li and Furkan Isik and Ibrahim Tanriover and Burak Guzelturk and Tze Chien Sum and Hilmi Volkan Demir},
journal= {arXiv preprint arXiv:1906.06913},
year = {2020}
}