A purely organic D-π-A-π-D emitter with thermally activated delayed fluorescence and room temperature phosphorescence for near-white OLED

A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) was designed and synthesized by utilizing the benzophenone as an acceptor and the N-phenyl-2-napthylamine as a donor moiety. It exhibits considerable TADF character in doped PMMA film and room temperature phosphorescence with a long lifetime of 74 ms at 466 nm in solid state. The devices with the configuration of ITO/Mo₂O₃ (4 nm)/mCP (30 nm)/mCP: x wt% NP2BP/TmTyPB (60 nm)/LiF (1.5 nm)/Al (100 nm) were prepared by vacuum evaporation to explore their electroluminescent performance. Interestingly, the non-doped device has obtained near-white emission with a fluorescence emission peak at 475 nm and a phosphorescence emission peak at 563 nm having the CIE coordinate of (0.23, 0.32) and the maximum external quantum efficiency of 1.09%.