We investigate a new strategy to enhance thermally activated delayed fluorescence (TADF) in organic light-emitting diodes (OLEDs). Given that the TADF rate of a molecule depends on its conformation, we hypothesize that there exists a conformation that maximizes the TADF rate. To test this idea, we use time-dependent density functional theory (TDDFT) to simulate the TADF rates of several TADF emitters while varying their geometries in a select subspace of internal coordinates. We find that geometric changes in this subspace can increase the TADF rate up to 3 orders of magnitude with respect to the minimum energy conformation, and the simulated TADF rate can even be brought into the submicrosecond time scales under the right conditions. Furthermore, the TADF rate enhancement can be maintained with a conformational energy that might be within the reach of modern synthetic chemistry. Analyzing the maximum TADF conformation, we extract a number of structural motifs that might provide a useful handle on the TADF rate of a donor–acceptor (DA) system. The incorporation of conformational engineering into the TADF technology could usher in a new paradigm of OLEDs.

中文翻译：

---

通过构象优化最大化 TADF

我们研究了一种增强有机发光二极管 (OLED) 中热激活延迟荧光 (TADF) 的新策略。鉴于分子的 TADF 速率取决于其构象，我们假设存在使 TADF 速率最大化的构象。为了测试这个想法，我们使用瞬态密度泛函理论 (TDDFT) 来模拟几个 TADF 发射器的 TADF 速率，同时在选定的内部坐标子空间中改变它们的几何形状。我们发现该子空间的几何变化可以将 TADF 速率相对于最小能量构象提高 3 个数量级，并且在适当的条件下，模拟的 TADF 速率甚至可以进入亚微秒时间尺度。此外，TADF 速率增强可以通过现代合成化学可能达到的构象能来维持。分析最大 TADF 构象，我们提取了许多结构基序，这些基序可能对供体 - 受体 (DA) 系统的 TADF 率提供有用的处理。将构象工程纳入 TADF 技术可能会开创 OLED 的新范式。