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

Nima Taghipour; Savas Delikanli; Sushant Shendre; Mustafa Sak; Mingjie Li; Furkan Isik; Ibrahim Tanriover; Burak Guzelturk; Tze Chien Sum; Hilmi Volkan Demir

doi:10.1038/s41467-020-17032-8

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

Nat Commun. 2020 Jul 3;11(1):3305. doi: 10.1038/s41467-020-17032-8.

Authors

Nima Taghipour¹, Savas Delikanli^{1

2}, Sushant Shendre², Mustafa Sak¹, Mingjie Li³, Furkan Isik¹, Ibrahim Tanriover¹, Burak Guzelturk⁴, Tze Chien Sum³, Hilmi Volkan Demir^{5

6

7}

Affiliations

¹ Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, 06800, Turkey.
² Luminous! Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
³ School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 639798, Singapore.
⁴ Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA.
⁵ Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, 06800, Turkey. volkan@stanfordalumni.org.
⁶ Luminous! Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore. volkan@stanfordalumni.org.
⁷ School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 639798, Singapore. volkan@stanfordalumni.org.

Abstract

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.