Hosoyamada Masanori, Yanai Nobuhiro, Ogawa Taku, Kimizuka Nobuo
Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka, 819-0395, Japan.
PRESTO, JST, Honcho 4-1-8, Kawaguchi, Saitama, 332-0012, Japan.
Chemistry. 2016 Feb;22(6):2060-2067. doi: 10.1002/chem.201503318. Epub 2016 Jan 8.
For real-world applications of photon upconversion based on the triplet-triplet annihilation (TTA-UC), it is imperative to develop solid-state TTA-UC systems that work effectively under low excitation power comparable to solar irradiance. As an approach in this direction, aromatic crystals showing high triplet diffusivity are expected to serve as a useful platform. However, donor molecules inevitably tend to segregate from the host acceptor crystals, and this inhomogeneity results in the disappointing performance of crystalline state TTA-UC. In this work, a series of cast-film-forming acceptors was developed, which provide both regular acceptor alignment and soft domains of alkyl chains that accommodate donor molecules without segregation. A typical triplet sensitizer, Pt octaethylporphyrin (PtOEP), was dispersed in these acceptor crystals without aggregation. As a result, efficient triplet energy transfer from the donor to the acceptor and diffusion of triplet excitons among regularly aligned anthracene chromophores occurred. It resulted in TTA-UC emission at low excitation intensities, comparable to solar irradiance.
对于基于三重态-三重态湮灭（TTA-UC）的光子上转换在实际中的应用，开发在与太阳辐照度相当的低激发功率下有效工作的固态TTA-UC系统势在必行。作为朝着这个方向的一种方法，具有高三重态扩散率的芳香族晶体有望成为一个有用的平台。然而，供体分子不可避免地倾向于从主体受体晶体中分离出来，这种不均匀性导致了晶态TTA-UC令人失望的性能。在这项工作中，开发了一系列形成流延膜的受体，它们既提供了规则的受体排列，又提供了烷基链的软区域，这些区域可以容纳供体分子而不会发生分离。一种典型的三重态敏化剂，铂八乙基卟啉（PtOEP），分散在这些受体晶体中而不发生聚集。结果，发生了从供体到受体的有效三重态能量转移以及三重态激子在规则排列的蒽发色团之间的扩散。这导致在低激发强度下产生TTA-UC发射，与太阳辐照度相当。
