We investigate the temperature dependence (from 16 K to 300 K) of an organic polariton laser, consisting of an amorphous organic semiconductor thin film in a planar microcavity. The polariton lasing threshold does not change between 45 K and room temperature, but increases when the temperature decreases below 45 K. This is accompanied by an energy relaxation bottleneck along the lower polariton branch at the lower temperature. This temperature dependence behavior is attributed to the competition between direct radiative pumping from exciton reservoir and phonon-induced relaxation at different temperature and explains the anomalously high thresholds in organic lasers.
Blue nanocrystal perovskite LEDs have traditionally lagged behind their red and green cousins. Here, we discuss the reasons for this lag and propose solutions to these problems, producing high efficiency blue perovskite LEDs. We demonstrate the NiOx, a transport material in one of the highest performing devices to date, reduces the performance of nanocrystals near to the interface. By replacing it with an alternative transport structure, we show that the nanocrystal emission is unperturbed. We then build full LEDs out of this transport structure, increasing the EQE from 0.03% to 0.50%, the highest for inorganic perovskite nanocrystals at this wavelength. We further show that the benefits of this transport structure relax as the energetics redshift, as our blue-green devices match those from literature. These results are a useful step forward towards commercially relevant perovskite LEDs.
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