World Scientific Reference on Spin in Organics - Volume 3: Magnetic Field Effects
World Scientific Reference on Spin in Organics - Volume 3: Magnetic Field Effects
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有机物自旋世界科学参考书 - 第 3 卷：磁场效应
DOI：
10.1142/9789813230194_0006
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Dias F
中科院分区：
文献类型：
--
作者：
Dias F
热激活延迟荧光（TADF）是近年来在有机电致发光器件（OLED）中获得三重态的最有吸引力的方法之一。文献中已经报道了大量的TADF分子，其目的是通过将非发射三重态转化为发射单重态来提高OLED的效率。TADF发射器能够通过荧光（即时和延迟）收获单重态和三重态，后者是由于热激活的反向系间穿越机制，允许低能量三重态上转换为发射单重态。这使得纯荧光OLED能够克服其25%内部量子效率（IQE）的固有限制，该内部量子效率是由电荷（电子和空穴）的复合产生的1：3的单线态-三线态比率所强加的。现在通常在绿色光谱区制造IQE接近100%的基于TADF的OLED。蓝色发光体也取得了重大进展。然而，红色发光体仍然显示出相对低的效率。尽管近年来已经取得了重大进展，但要充分理解TADF机制并提高这些材料的稳定性，仍然存在重大挑战。这些问题需要得到解决，以便在OLED中全面实施TADF并将其应用扩展到其他领域。迄今为止，TADF主要在OLED领域中被开发，但设想在其他领域中的应用，例如传感和荧光显微镜。在这篇综述中，TADF分子的物理性质进行了讨论，总结了目前的方法，这些材料和TADF机制在各种分子系统的理解。
Thermally activated delayed fluorescence (TADF) has recently emerged as one of the most attractive methods for harvesting triplet states in metal-free organic materials for application in organic light emitting diodes (OLEDs). A large number of TADF molecules have been reported in the literature with the purpose of enhancing the efficiency of OLEDs by converting non-emissive triplet states into emissive singlet states. TADF emitters are able to harvest both singlets and triplet states through fluorescence (prompt and delayed), the latter due to the thermally activated reverse intersystem crossing mechanism that allows up-conversion of low energy triplet states to the emissive singlet level. This allows otherwise pure fluorescent OLEDs to overcome their intrinsic limit of 25% internal quantum efficiency (IQE), which is imposed by the 1: 3 singlet–triplet ratio arising from the recombination of charges (electrons and holes). TADF based OLEDS with IQEs close to 100% are now routinely fabricated in the green spectral region. There is also significant progress for blue emitters. However, red emitters still show relatively low efficiencies. Despite the significant progress that has been made in recent years, still significant challenges persist to achieve full understanding of the TADF mechanism and improve the stability of these materials. These questions need to be solved in order to fully implement TADF in OLEDs and expand their application to other areas. To date, TADF has been exploited mainly in the field of OLEDs, but applications in other areas, such as sensing and fluorescence microscopies, are envisaged. In this review, the photophysics of TADF molecules is discussed, summarising current methods to characterise these materials and the current understanding of the TADF mechanism in various molecular systems.