Organic light-emitting diodes (OLEDs) radiating near ultraviolet (NUV) light are of high importance but rarely reported due to the lack of robust organic short-wavelength emitters. Here, we report a short π-conjugated molecule (POPCN-2CP) with high thermal and morphological stabilities and strong NUV photoluminescence. Its neat film exhibits an electroluminescence (EL) peak at 404 nm with a maximum external quantum efficiency (η ext,max ) of 7.5 % and small efficiency roll-off. The doped films of POPCN-2CP in both non-polar and polar hosts at a wide doping concentration range (10-80 wt%) achieve high-purity NUV light (388-404 nm) and excellent η ext,max s of up to 8.2 %. The highlevel reverse intersystem crossing improves exciton utilization and accounts for the superb η ext,max s. POPCN-2CP can also serve as an efficient host for blue fluorescence, thermally activated delayed fluorescence and phosphorescence emitters, providing excellent EL performance via Förster energy transfer.

Severe efficiency instability is still a huge challenge for most organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) molecules, frustrating their industrial application. To address this issue, herein we report two robust luminogens, 3,6-bis(9,9-dimethylacridin-10-yl)-xanthen-9-one (BDMAC-XT) and 3,6-bis(9,9-diphenylacridin-10)-yl)-xanthen-9-one (BDPAC-XT), comprised of electron-accepting 3,6-dibromoxanthen-9-one and electron-donating 9,9-dimethyl-9,10-dihydroacridine and 9,9-diphenyl-9,10-dihydroacridine. BDMAC-XT and BDPAC-XT show interesting aggregationenhanced delayed fluorescence characteristics with excellent photoluminescence quantum yields of 96% and 94% in neat films. Nondoped OLEDs based on BDMAC-XT emit intense green light with high external quantum yields (η ext ; 21%) and hardly any efficiency roll-off (∼0%) at 1000 cd m −2 . High-performance sky-blue nondoped OLEDs are achieved using BDPAC-XT as emitter, providing impressive η ext values (21%). Both luminogens can also function efficiently as dopants in doped OLEDs, furnishing excellent η ext values (27%) and very small efficiency roll-offs down to 3.7% at 1000 cd m −2 . Moreover, they can perform as excellent hosts for orange and red phosphorescent OLEDs, leading to η ext values of up to 26% and 20%, respectively. These results demonstrate that they are promising versatile functional materials for high-efficiency nondoped and doped OLEDs with superb efficiency stability.

Organic light-emitting diodes (OLEDs) radiating near ultraviolet (NUV) light are of high importance but rarely reported due to the lack of robust organic short-wavelength emitters. Here, we report a short π-conjugated molecule (POPCN-2CP) with high thermal and morphological stabilities and strong NUV photoluminescence. Its neat film exhibits an electroluminescence (EL) peak at 404 nm with a maximum external quantum efficiency (η ext,max ) of 7.5 % and small efficiency roll-off. The doped films of POPCN-2CP in both non-polar and polar hosts at a wide doping concentration range (10-80 wt%) achieve high-purity NUV light (388-404 nm) and excellent η ext,max s of up to 8.2 %. The highlevel reverse intersystem crossing improves exciton utilization and accounts for the superb η ext,max s. POPCN-2CP can also serve as an efficient host for blue fluorescence, thermally activated delayed fluorescence and phosphorescence emitters, providing excellent EL performance via Förster energy transfer.