Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan.
Institute of Atomic and Molecular Science , Academia Sinica , Taipei 10617 , Taiwan.
ACS Appl Mater Interfaces. 2018 Jun 13;10(23):19279-19304. doi: 10.1021/acsami.7b18318. Epub 2018 Apr 10.
Organic materials that display thermally activated delayed fluorescence (TADF) are a striking class of functional materials that have witnessed a booming progress in recent years. In addition to pure TADF emitters achieved by the subtle manipulations of intramolecular charge transfer processes with sophisticated molecular structures, a new class of efficient TADF-based OLEDs with emitting layer formed by blending electron donor and acceptor molecules that involve intermolecular charge transfer have also been fabricated. In contrast to pure TADF materials, the exciplex-based systems can realize small Δ E (0-0.05 eV) much more easily since the electron and hole are positioned on two different molecules, thereby giving small exchange energy. Consequently, exciplex-based OLEDs have the prospective to maximize the TADF contribution and achieve theoretical 100% internal quantum efficiency. Therefore, the challenging issue of achieving small Δ E in organic systems could be solved. In this article, we summarize and discuss the latest and most significant developments regarding these rapidly evolving functional materials, wherein the majority of the reported exciplex forming systems are categorized into two subgroups, viz. (a) exciplex as TADF emitters and (b) those as hosts for fluorescent, phosphorescent and TADF dopants according to their structural features and applications. The working mechanisms of the direct electroluminescence from the donor/acceptor interface and the exciplex-forming systems as cohost for the realization of high efficiency OLEDs are reviewed and discussed. This article delivers a summary of the current progresses and achievements of exciplex-based researches and points out the future challenges to trigger more research endeavors to this growing field.
具有热激活延迟荧光（TADF）特性的有机材料是一类引人注目的功能材料，近年来取得了蓬勃的发展。除了通过精巧的分子结构对分子内电荷转移过程进行精细调控而获得的纯 TADF 发射器外，还制备了一类新型高效 TADF 基于 OLED，其发射层由电子给体和受体分子形成，涉及分子间电荷转移。与纯 TADF 材料相比，基于激基复合物的系统更容易实现小的 ΔE（0-0.05 eV），因为电子和空穴位于两个不同的分子上，从而赋予小的交换能。因此，基于激基复合物的 OLED 有可能最大限度地发挥 TADF 的贡献，并实现理论上的 100%内部量子效率。因此，可以解决有机体系中实现小的 ΔE 的挑战性问题。在本文中，我们总结和讨论了这些快速发展的功能材料的最新和最重要的进展，其中大多数报道的激基复合物形成系统根据其结构特征和应用分为两类，即（a）激基复合物作为 TADF 发射器，和（b）作为荧光、磷光和 TADF 掺杂剂的主体的那些。根据供体/受体界面的直接电致发光和激基复合物形成系统作为实现高效率 OLED 的共主体的工作机制进行了综述和讨论。本文总结了基于激基复合物的研究的当前进展和成就，并指出了未来的挑战，以激发该不断发展的领域的更多研究努力。
