- Benchmarking of Density Functionals for the Description of Optical Properties of Newly Synthesized π-Conjugated TADF Blue Emitters
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Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light-emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial. In the current study, we focus on testing the performance of a set of DFT functionals for estimation of the excitation and emission energy and the excited singlet-triplet energy gap of three newly synthesized compounds with capacity for TADF. The emitters are designed specifically to enable charge transfer by π-electron conjugation, at the same time possessing high-energy excited triplet states. The functionals chosen for testing are from various groups ranging from gradient-corrected through global hybrids to range-separated ones. The results show that the monitored optical properties are especially sensitive to how the long-range part of the exchange energy is treated within the functional. The accurate functional should also be able to provide well balanced distribution of the π-electrons among the molecular fragments. Global hybrids with moderate (less than 0.4) share of exact exchange (B3LYP, PBE0) and the meta-GGA HSE06 are outlined as the best performing methods for the systems under study. They can predict all important optical parameters correctly, both qualitatively and quantitatively.
- Ivanova, Georgia,Bozova, Nadezhda,Petkov, Nikolay,An, Cunbin,Hu, Benlin,Mutovska, Monika,Konstantinov, Konstantin,Zagranyarski, Yulian,Videva, Vladimira,Yordanova, Adelina,Baumgarten, Martin,Ivanova, Anela
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supporting information
(2022/02/22)
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- Synthesis and physical properties of meta-terphenyloxadiazole derivatives and their application as electron transporting materials for blue phosphorescent and fluorescent devices
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Two m-terphenyloxadiazole-based electron transporting materials, bis(2-tert-butyl-1,3,4-oxadiazole-5-diyl)-3,3′-m-terphenyl (tOXD-mTP) and bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazole-5-diyl)-3,3′-m-terphenyl (tpOXD-mTP) were synthesized and characterized. These two molecules contained two oxadiazolyl groups and a m-terphenyl linkage as the core structure achieving high triplet energy gaps (ET) of 2.83 and 2.90 eV, respectively. The application of tOXD-mTP and tpOXD-mTP as the electron transporting materials (ETM) in bis(4′,6′-difluorophenylpyridinato)-iridium(iii) picolinate (FIrpic)-based blue phosphorescent light-emitting devices effectively confines the triplet exciton in the emitting layers. One of the electroluminescent (EL) devices using FIrpic as the dopant showed an excellent current efficiency of 43.3 cd A-1 and an external quantum efficiency (EQE) of 23.0% with CIE (Commission International de l'Eclairage) coordinates of (0.13, 0.29). The bis(4′,6′-difluorophenylpyridinato)-iridium(iii) tetra(1-pyrazolyl)borate (FIr6)-based deeper blue EL device exhibited a high current efficiency of 42.5 cd A-1 and external quantum efficiency of 25.0% with CIE coordinates of (0.14, 0.23). These two tOXD-mTP and tpOXD-mTP based devices show device efficiencies two to three times higher than that based on the well-known electron transporting material 1,3-bis[(4-tertbutylphenyl)-1, 3,4-oxadiazolyl]phenylene (OXD-7).
- Wu, Cheng-An,Chou, Ho-Hsiu,Shih, Cheng-Hung,Wu, Fang-Iy,Cheng, Chien-Hong,Huang, Heh-Lung,Chao, Teng-Chih,Tseng, Mei-Rurng
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p. 17792 - 17799
(2012/09/22)
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