ABSTRACT
Cs2TiBr6 stands as a promising Pb-free alternative perovskite material having demonstrated its potential in photovoltaics. However, it is considered to be highly unstable in air, hindering further improvements and raising concerns regarding its practical implementation. In this work, we report on a method to improve the stability of Cs2TiBr6 NCs using SnBr4 in a facile surface treatement.
ABSTRACT
The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485 ps, lowering the amplified spontaneous emission (ASE) threshold down to 300 µJ cm-2 , and showing a record high net modal gain coefficient of 2180 cm-1 . By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot ãNth ãg of 0.45 due to bleaching of the ground state absorption. This in turn have led to a fivefold reduction in ASE threshold at ãNth ãASE = 0.70 excitons-per-dot, associated with a gain lifetime of 280 ps. Finally, these heterostructured QDs are used to achieve near-infrared lasing at 1670 nm at a pump fluences corresponding to sub-single-exciton-per-dot threshold (ãNth ãLas = 0.87). This work brings infrared CQD lasing thresholds on par to their visible counterparts, and paves the way toward solution-processed infrared laser diodes.
