Robust Luminescent Molecules with High‐Level Reverse Intersystem Crossing for Efficient Near Ultraviolet Organic Light‐Emitting Diodes.

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 (ηext,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 ηext,maxs of up to 8.2 %. The high‐level reverse intersystem crossing improves exciton utilization and accounts for the superb ηext,maxs. 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. [ABSTRACT FROM AUTHOR]