Organic light-emitting devices (OLEDs) containing organic molecules that exhibit thermally activated delayed fluorescence (TADF) produce high efficiencies. One challenge to the commercialization of the TADF OLEDs that remains to be addressed is their operational stability. Here we investigate the molecular factors that govern the stability of various archetypal TADF molecules based on a cycloamino donor–acceptor platform. Our results reveal that the intrinsic stability depends sensitively on the identity of the cycloamino donors in the TADF compounds. The rates and photochemical quantum yields of the degradation are positively correlated with the operation lifetimes of the devices. Our research shows that the stability is governed by the conformeric heterogeneity between the pseudo-axial and pseudo-equatorial forms of the cycloamino donor. Spontaneous bond dissociation occurs in the former (i.e., the pseudo-axial form), but the cleavage is disfavored in the pseudo-equatorial form. These findings provide valuable insights into the design of stable TADF molecules.

包含表现出热激活延迟荧光 (TADF) 的有机分子的有机发光器件 (OLED) 可产生高效率。仍有待解决的 TADF OLED 商业化的一个挑战是它们的操作稳定性。在这里，我们研究了基于环氨基供体-受体平台控制各种原型 TADF 分子稳定性的分子因素。我们的结果表明，内在稳定性敏感地取决于 TADF 化合物中环氨基供体的特性。降解的速率和光化学量子产率与器件的使用寿命呈正相关。我们的研究表明，稳定性受环氨基供体的伪轴向和伪赤道形式之间的构象异构异质性控制。自发键解离发生在前者（即伪轴向形式）中，但在伪赤道形式中不利于分裂。这些发现为稳定 TADF 分子的设计提供了宝贵的见解。