Sukanya TongsukRuttapol MalatongTakdanai UnjarernChanikan WongkaewPanida SurawatanawongTaweesak SudyoadsukVinich PromarakNopporn RuangsupapichatVidyasirimedhi Institute of Science and TechnologyMahidol University2022-08-042022-08-042021-10-01Journal of Luminescence. Vol.238, (2021)002223132-s2.0-85109012753https://repository.li.mahidol.ac.th/handle/20.500.14594/76017Recently, considerable efforts have been devoted to the improvement of fluorescent OLEDs because of their affordable cost and metal-free materials. Indolo[3,2-b]indole derivatives with a large planar rigid structure and great photophysical properties have attracted attentions as materials in a variety of organic electronics but their applications as OLEDs are still limited. Herein, we reported two new fluorescent OLEDs, i.e., 10,10'-(sulfonylbis(4,1-phenylene))bis(5-ethyl-5,10-dihydroindolo[3,2-b]indole) (DHID-DPS) and 2,8-bis(10-butylindolo[3,2-b]indol-5(10H)-yl)dibenzo[b,d]thiophene 5,5-dioxide (DHID-DBS), with a distorted donor-acceptor-donor structure bearing indolo[3,2-b]indole moieties as electron-donors. The DHID-DPS exhibited a smaller singlet-triplet energy gap (ΔEST = 0.18 eV) than DHID-DBS (ΔEST = 0.33 eV). In addition, DHID-DPS demonstrated the fluorescence quantum yield in doped films reaching to 32% as well as the evidence of thermally activated delayed fluorescence (TADF) properties. As a result, the optimized doped OLED by using DHID-DPS as an emitter achieved a maximum external quantum efficiency of 3.86% with a blue-green fluorescence as well as a high brightness up to 12860 cd m−2. This suggested that indolo[3,2-b]indole derivatives are potential candidates for donor moieties in OLED applications.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyChemistryPhysics and AstronomyArticleSCOPUS10.1016/j.jlumin.2021.118287