Near-ultraviolet organic light emitting diodes using melem

This study fabricates near-ultraviolet (NUV)-organic light-emitting diodes (NUV-OELDs) using 2,5,8-triamino-tri-s-triazine (melem) as the emitting layer. Melem exhibits NUV emission owing to thermally activated delayed fluorescence. However, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO--LUMO) gap of melem is large, thus rendering difficulty in carrier injection from the electrodes and causing the carrier injection layer or carrier transport layer to emit light. Therefore, in this study, the device structure of the NUV-OLED is optimized to obtain melem-derived luminescence using carrier transport materials with a large HOMO-LUMO gap. Consequently, NUV-OLED with emission in the NUV region is successfully realized.