Not the sum of their parts: understanding multi-donor interactions in symmetric and asymmetric TADF emitters
Not the sum of their parts: understanding multi-donor interactions in symmetric and asymmetric TADF emitters
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DOI：
10.1039/d1tc04171a
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发表时间：
2021-11-18
影响因子：
6.4
通讯作者：
Monkman, Andrew P.
中科院分区：
文献类型：
--
作者：
Danos, Andrew;Gudeika, Dalius;Monkman, Andrew P.
研究了一对具有对称和非对称D-A-D结构的热激活延迟荧光（TADF）发光体。尽管显示出几乎相同的光致发光光谱和量子产率，但对称材料具有显著更好的延迟荧光特性和OLED性能。建立在以前的研究类似的D-A材料，我们能够解释这些差异的两个捐助单位之间的电子相互作用的不同强度。这种相互作用降低了不对称分子中TADF活性三重态的能量，增加了其单重态-三重态能隙并导致更差的性能。因此，该结果证明了选择性控制TADF分子的三重态的新策略，与使用主体环境的单重态的已建立的控制相反。这些结果还表明，多供体TADF发射体不能简单地理解为它们的孤立部分的总和;这些部分根据它们的相对位置具有不同的电子相互作用，即使没有空间相互作用的范围。
A pair of thermally activated delayed fluorescence (TADF) emitters with symmetric and asymmetric D-A-D structure are investigated. Despite displaying near-identical photoluminescence spectrum and quantum yields, the symmetric material possesses significantly better delayed fluorescence characteristics and OLED performance. Building on a previous study of analogous D-A materials we are able to explain these differences in terms of different strengths of electronic interactions between the two donor units. This interaction lowers the energy of the TADF-active triplet state in the asymmetric molecule, increasing its singlet-triplet energy gap and leading to worse performance. This result therefore demonstrates a new strategy to selectively control the triplet states of TADF molecules, in contrast to established control of singlet states using host environment. These results also show that multi-donor TADF emitters cannot be understood simply as the sum of their isolated parts; these parts have different electronic interactions depending on their relative positions, even when there is no scope for steric interaction.