  The aerobic and thermal stability of quantum-dot light-emitting diodes
(QLEDs) is an important factor for the practical applications of these devices
under harsh environmental conditions. In this paper, we demonstrate
all-solution-processed amber QLEDs with an external quantum efficiency (EQE) of
>14% with almost negligible efficiency roll-off (droop) and a peak brightness
of >600,000 cd/m2, unprecedented for QLEDs fabricated under ambient air
conditions. We investigate the device efficiency and brightness level at a
temperature range between -10 C to 85 C in a 5-step cooling/heating cycle.
Unlike previous studies reported in the literature, we conducted the
experiments at relatively high brightness levels, required for outdoor lighting
applications. The results reveal that the device performance increases slightly
at sub-zero temperatures (-10 C) and drops slightly at very high temperatures
(85 C), proving acceptable thermal stability. Overall, the performance
parameters do not change dramatically over the temperature range within the
experimental uncertainty range. Interestingly, the device efficiency parameters
recover to the initial values upon returning to room temperature. The
variations in the performance are correlated with the modification of charge
transport characteristics and induced radiative/non-radiative exciton
relaxation dynamics at different temperatures. Being complementary to previous
studies on the subject, the present work is expected to shed light on the
potential feasibility of realizing aerobic-stable ultrabright droop-free QLEDs
and encourage further research for solid-state lighting applications.
