Kashino Tsubasa, Haruki Rena, Uji Masanori, Harada Naoyuki, Hosoyamada Masanori, Yanai Nobuhiro, Kimizuka Nobuo
Department of Applied Chemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
Nissan Chemical Corporation, Funabashi 274-0069, Japan.
ACS Appl Mater Interfaces. 2022 Jan 11. doi: 10.1021/acsami.1c17021.
For the practical application of triplet-triplet annihilation-based photon upconversion (TTA-UC), the development of rigid, transparent, air-stable, and moldable materials with a high TTA-UC efficiency remains a challenging issue. In addition to the noncovalent introduction of ionic liquid emitters into the epoxy network, we covalently introduce emitters with polymerization sites to increase the emitter concentration to 35.6 wt %. A TTA-UC quantum yield Φ of 5.7% (theoretical maximum: 50%) or a TTA-UC efficiency η of 11.4% (theoretical maximum: 100%) is achieved, which is the highest value ever achieved for a rigid polymer material. More importantly, the high emitter concentration speeds up the triplet diffusion and suppresses the back energy transfer from the emitter to sensitizer so that the sensitized emitter triplet can be effectively utilized for TTA. The generality of our finding is also confirmed for epoxy resins of similar emitter unit concentrations without the ionic liquid. This work provides important design guidelines for achieving highly efficient TTA-UC in rigid solid materials, which has been very difficult to achieve in the past. Furthermore, the solid-state TTA-UC exhibits high air stability, reflecting the high oxygen barrier performance of epoxy resins. The high moldability of epoxy resins allows the construction of upconversion materials with complex geometries at nano- to macroscopic scales.
对于基于三重态-三重态湮灭的光子上转换（TTA-UC）的实际应用而言，开发具有高TTA-UC效率的刚性、透明、空气稳定且可模塑的材料仍然是一个具有挑战性的问题。除了将离子液体发射体非共价引入环氧网络外，我们还共价引入具有聚合位点的发射体，将发射体浓度提高到35.6 wt%。实现了5.7%的TTA-UC量子产率Φ（理论最大值：50%）或11.4%的TTA-UC效率η（理论最大值：100%），这是刚性聚合物材料所达到的最高值。更重要的是，高发射体浓度加快了三重态扩散，并抑制了从发射体到敏化剂的反向能量转移，从而使敏化的发射体三重态能够有效地用于TTA。对于不含离子液体的类似发射体单元浓度的环氧树脂，我们的发现的普遍性也得到了证实。这项工作为在刚性固体材料中实现高效TTA-UC提供了重要的设计指导原则，而这在过去一直很难实现。此外，固态TTA-UC表现出高空气稳定性，这反映了环氧树脂的高氧气阻隔性能。环氧树脂的高可模塑性允许构建纳米到宏观尺度上具有复杂几何形状的上转换材料。
