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Photophysics of OLED Materials with Emitters Exhibiting Thermally Activated Delayed Fluorescence and Used in Hole/Electron Transporting Layer from Optimally Tuned Range-Separated Density Functional Theory
- Alipour, Mojtaba, Safari, Zahra
- Journal of physical chemistry 2018 v.123 no.1 pp. 746-761
- absorption, density functional theory, energy, fluorescence, light emitting diodes, models, prediction
- Owing to their potential to be exploited as emitters in heavy metal-free organic light emitting diodes (OLEDs), the interest toward the molecules exhibiting thermally activated delayed fluorescence (TADF) and used in hole/electron transporting layer has been reinvigorated in recent years. In the present contribution, we take a different approach to deal with the problem where the novel optimally tuned range-separated hybrid density functionals (OT-RSHs) are developed for reliable description of the photophysical properties like absorption, emission, and singlet–triplet energies for the emitters covering a wide range of singlet–triplet energy gaps. Considering BLYP, PBE, and TPSS density functional approximations as the underlying exchange and correlation terms with different options for the short- and long-range exact-like exchange contributions as well as the range-separation parameter, we propose several OT-RSHs for accurate predictions of the photophysical properties in both gas and solution phases for a set of compounds prone to be employed in OLED materials. It is shown that newly developed OT-RSHs with correct asymptotic exchange-correlation potential behavior provide reliable theoretical estimates of photophysics for an experimental benchmark set of compounds. We find that the proposed models not only have superior performance with respect to the standard counterparts but also outperform the earlier developed hybrids with both fixed and interelectronic distance-dependent exact-like exchange. Promisingly, such good performances are also indeed the case for other emitters not included in optimally tuning processes of the range-separation parameter. As showcased by our theoretical explorations on the photophysics of OLEDs and other earlier efforts in this arena of research, it seems that a bright future lies ahead.