Analysis of efficiency variations in ν-DABNA based thermally activated delayed fluorescence OLED devices

Recently, diboron based blue thermally activated delayed fluorescence (TADF) material, N7,N7,N13,N13,5,9,11,15-octaphenyl-5,9,11,15-tetrahydro-5,9,11,15-tetraaza-19b, 20b-diboradinaphtho[3,2,1-de:1′,2′,3′-jk] pentacene-7,13-diamine (ν-DABNA) has drawn attention from the researchers due to its good device performances as well as narrow full-width at half maximum (FWHM) in OLED devices. In this work, we report a detailed analysis to understand the exact reason behind the efficiency variations in ν-DABNA based TADF devices using different types of host materials. Interestingly, we found that triplet exciton density of ν-DABNA molecule is mainly located at the central region, so the triplet exciton energy transfer from the host material is hindered due to the presence of peripheral diphenylamine extensions. Hence, our analysis suggests that utilizing wide band gap host materials in ν-DABNA based TADF devices exhibit excellent device efficiencies with the support of trap assisted emission mechanism. This study brings an in-depth understanding of efficiency variations in the ν-DABNA based OLED devices.