Journal
ACS PHOTONICS
Volume 4, Issue 3, Pages 576-583Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsphotonics.6b00890
Keywords
quantum wells; CdS; amplified spontaneous emission; lasing; trapping
Categories
Funding
- NSF DMREF Program [DMR-1629601, DMR-1629383]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1629601] Funding Source: National Science Foundation
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Amplified spontaneous emission (ASE) and lasing from solution-processed materials are demonstrated in the challenging violet-to-blue (430-490 nm) spectral region for colloidal nanoplatelets of CdS and newly synthesized core/shell CdS/ZnS nanoplatelets. Despite modest band-edge photoluminescence quantum yields of 2% or less for single excitons, which we show results from hole trapping, the samples exhibit low ASE thresholds. Furthermore, four-monolayer CdS samples show ASE at shorter wavelengths than any reported film of colloidal quantum-confined material. This work underlines that low quantum yields for single excitons do not necessarily lead to a poor gain medium. The low ASE thresholds originate from negligible dispersion in thickness, large absorption cross sections of 2.8 X 10(-14) cm(-2), and rather slow (150 to 300 ps) biexciton recombination. We show that under higher-fluence excitation, ASE can kinetically outcompete hole trapping. Using nanoplatelets as the gain medium, lasing is observed in a linear optical cavity. This work confirms the fundamental advantages of colloidal quantum well structures as gain media, even in the absence of high photoluminescence efficiency. [GRAPHICS]
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