One of the requirements to design efficient emitters based on the multiresonance (MR)- or donor–acceptor (D-A) thermally activated delayed fluorescence (TADF) materials is a relatively small energy gap between the lowest singlet and triplet excited states (ΔE_ST). High-level ab initio calculations of their ΔE_ST provide benchmark results, but they are very time consuming and little practical for large-size systems. Here, the performances of hole–hole Tamm–Dancoff approximated density functional theory (hh-TDA-DFT) and the functional dependent accuracy of hh-TDA are examined on ΔE_ST of a large number of MR- and D-A TADF molecules. The results indicate that hh-TDA combined with the hybrid functional B3LYP can predict ΔE_ST values for a wide number of MR-TADF molecules with mean absolute error (MAE) within 0.04 eV with correlation as high as 0.75. For D-A TADF molecules, ΔE_ST is less sensitive to the nature of the functionals, with MAE as low as 0.07 eV. The larger discrepancy between ΔE_ST obtained from hh-TDA-DFT and experimental data in several oxygen-containing MR-TADF molecules is assumed to stem from the aggregation tendency of these compounds in solution. These findings provide important insights on the role of aggregation in reducing the ΔE_ST of MR-TADF compounds.

中文翻译：

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使用 Hole-Hole Tamm-Dancoff 近似密度泛函理论快速准确测定供体-受体和多共振 TADF 分子中的单重态-三重态间隙

设计基于多共振 (MR) 或供体-受体 (DA) 热激活延迟荧光 (TADF) 材料的高效发射器的要求之一是最低单重激发态和三重激发态 (Δ E _ST )之间的能隙相对较小. 对其 Δ E _ST的高级从头计算提供了基准结果，但它们非常耗时且对于大型系统几乎不实用。在这里，在大量 MR-和 DA TADF 分子的ΔE _ST上检查了孔-孔 Tamm-Dancoff 近似密度泛函理论 (hh-TDA-DFT) 的性能和 hh-TDA 的功能依赖精度。结果表明，hh-TDA 与混合功能 B3LYP 结合可以预测 Δ大量 MR-TADF 分子的E _ST值，平均绝对误差 (MAE) 在 0.04 eV 内，相关性高达 0.75。对于 DA TADF 分子，ΔE _ST对官能团的性质不太敏感，MAE 低至 0.07 eV。从 hh-TDA-DFT 获得的 Δ E _ST与几种含氧 MR-TADF 分子中的实验数据之间较大的差异被认为是由于这些化合物在溶液中的聚集趋势。这些发现提供了关于聚集在降低MR-TADF 化合物的ΔE _{ST中的作用的重要见解。}