mMDBA-DI, namely 5-(3, 11-dimethyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10,15-diphenyl-10,15-dihydro-5H-diindolo[3, 2-a:3′, 2′-c]carbazole, is a D-A type MR-TADF emitter that features a faster kRISC of 1.5 × 106 s−1. Among the developed TADF sensitizers, the mMDBA-DI demonstrates deep blue color with a high horizontal dipole orientation ratio of 0.82 and PLQY of 97.8%. mMDBA-DI has large spectrum overlap with v-DABNA, hyperfluorescence (HF) device with mMDBA-DI exhibits EQEmax of 39.9% with max electroluminescence of 474 nm and 19 nm of FWHM.
Also, Hyperfluorescence device based on TADF host material, mMDBA-DI, and a pure blue multi-resonance type tert-butyl substituted TADF fluorescence emitter t-Bu-ν-DABNA exhibits a high external quantum efficiency of 39.1% along with narrow emission with full width at half maximum of 19 nm (CIE y = 0.15).