Two-band optical gain and ultrabright electroluminescence from colloidal quantum dots at 1000 A cm-2

Heeyoung Jung; Young-Shin Park; Namyoung Ahn; Jaehoon Lim; Igor Fedin; Clément Livache; Victor I Klimov

doi:10.1038/s41467-022-31189-4

Two-band optical gain and ultrabright electroluminescence from colloidal quantum dots at 1000 A cm^-2

Nat Commun. 2022 Jun 29;13(1):3734. doi: 10.1038/s41467-022-31189-4.

Authors

Heeyoung Jung¹, Young-Shin Park^{1

2}, Namyoung Ahn¹, Jaehoon Lim^{1

3}, Igor Fedin¹, Clément Livache¹, Victor I Klimov⁴

Affiliations

¹ Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
² Centre for High Technology Materials, University of New Mexico, Albuquerque, NM, 87131, USA.
³ Department of Energy Science and Centre for Artificial Atom, Sungkyunkwan University, Natural Sciences Campus, Seobu-ro 2066, Jangan-gu, Suwon, 16419, Gyeonggi-do, Republic of Korea.
⁴ Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA. klimov@lanl.gov.

Abstract

Colloidal quantum dots (QDs) are attractive materials for the realization of solution-processable laser diodes. Primary challenges towards this objective are fast optical-gain relaxation due to nonradiative Auger recombination and poor stability of colloidal QD solids under high current densities required to obtain optical gain. Here we resolve these challenges and achieve broad-band optical gain spanning the band-edge (1S) and the higher-energy (1P) transitions. This demonstration is enabled by continuously graded QDs with strongly suppressed Auger recombination and a current-focusing device design, combined with short-pulse pumping. Using this approach, we achieve ultra-high current densities (~1000 A cm^-2) and brightness (~10 million cd m^-2), and demonstrate an unusual two-band electroluminescence regime for which the 1P band is more intense than the 1S feature. This implies the realization of extremely large QD occupancies of up to ~8 excitons per-dot, which corresponds to complete filling of the 1S and 1P electron shells.