Achieving High Efficiency and Pure Blue Color in Hyperfluorescence Organic Light Emitting Diodes using Organo-Boron Based Emitters

Abstract

In the field of organic light emitting diodes (OLEDs), organo-boron based thermally activated delayed fluorescence (TADF) emitters have reached great achievement. However, it is still challenging to achieve pure blue color (CIE y < 0.20) along with high efficiencies. To overcome these hurdles, hyperfluorescence (HF) suggest a key strategy in future OLED applications. Here, we report two TADF materials, pMDBA-DI and mMDBA-DI. Further, a pure blue multi resonance type tert-butyl substituted fluorescence emitter, t-Bu-ν-DABNA was also synthesized. Among our synthesized TADF materials based pure blue HF devices, mMDBA-DI as TADF sensitized host with t-Bu-ν-DABNA fluorescence emitter exhibited a high external quantum efficiency of 40.7% (Lambertian assumption) along with narrow emission with full width at half maximum of 19 nm (CIE y = 0.15). Moreover, we analyzed that such high device efficiency is mainly attributed to the high orientation factor, enhanced photoluminescence quantum yield, and a good TADF characteristic of t-Bu-ν-DABNA with high Förster resonance energy transfer.