Organic molecular materials with high fluorescence quantum yields over 90% in the near-ultraviolet region

Near ultraviolet (NUV)-emitting materials are expected to have a wide range of applications. However, their exploration has lagged behind that of visible-light-emitting materials, and no material showing highly efficient NUV emission has been reported. In this study, we synthesized a hydrate of 2,5,8-triamine tri-s-triazine (melem), a thermally activated delayed fluorescence (TADF) molecule that emits light in the NUV region, and subsequently completely dehydrated it to produce a new NUV-emitting material. As a result, we developed a TADF material that emits light in the NUV region with a very high photoluminescence quantum yield of over 90%. Furthermore, we found that melem hydrates with a large amount of water molecules strongly bound to the molecular framework, emit light at a wavelength of approximately 350 nm, the shortest for NUV light emitted by TADF molecules. These results are expected to provide new insights for future exploration and development of NUV-emitting materials for light-emitting devices such as organic light-emitting diodes (OLEDs).