Kashino Tsubasa, Hosoyamada Masanori, Haruki Rena, Harada Naoyuki, Yanai Nobuhiro, 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.
Nissan Chemical Corporation, Funabashi 274-0069, Japan.
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):13676-13683. doi: 10.1021/acsami.0c23121. Epub 2021 Mar 3.
It remains challenging to achieve efficient and air-stable photon upconversion (UC) in rigid, technologically valuable transparent films. Here, we report the first example of epoxy resins that show an air-stable and efficient triplet-triplet annihilation (TTA)-based UC. Epoxy resins are thermally cross-linked polymers widely used as coating and sealing materials in actual devices. To achieve efficient TTA-UC in rigid epoxy films, it is essential to execute both the triplet sensitization and triplet exciton diffusion processes without relying on molecular diffusion. This requires homogeneously dispersing emitter molecules without aggregation in three-dimensionally cross-linked rigid polymer networks at a high concentration (ca. 1000 mM) such that the inter-emitter distance is less than 1 nm, where dexter energy transfer can occur. This difficult requirement is solved by employing an ionic liquid emitter that consists of 9,10-diphenylanthracene sulfonate and lipophilic phosphonium ions bearing long alkyl chains. The obtained epoxy resins show a high TTA-UC efficiency (η = 3.8%) and low threshold excitation intensity ( = 40 mW cm) in air. These UC parameters are achieved by virtue of a very high sensitizer-to-emitter triplet energy-transfer efficiency (92.8%) and a significantly long emitter triplet lifetime (17.8 ms) that reflect the high emitter concentration and the rigid chromophore environment, respectively. The bulk transparent upconverting resins can be prepared in air and function in air, which opens a new avenue toward a wide range of real-world applications.
在刚性且具有技术价值的透明薄膜中实现高效且空气稳定的光子上转换（UC）仍然具有挑战性。在此，我们报道了首例基于三重态 - 三重态湮灭（TTA）的空气稳定且高效的环氧树脂。环氧树脂是热交联聚合物，在实际器件中广泛用作涂层和密封材料。要在刚性环氧薄膜中实现高效的TTA - UC，在不依赖分子扩散的情况下执行三重态敏化和三重态激子扩散过程至关重要。这需要在三维交联的刚性聚合物网络中以高浓度（约1000 mM）均匀分散发射体分子而不发生聚集，使得发射体间距离小于1 nm，在此距离下可以发生德克斯特能量转移。通过使用由9,10 - 二苯基蒽磺酸盐和带有长烷基链的亲脂性鏻离子组成的离子液体发射体解决了这一苛刻要求。所制备的环氧树脂在空气中显示出高TTA - UC效率（η = 3.8%）和低阈值激发强度（ = 40 mW cm）。这些UC参数得益于非常高的敏化剂到发射体的三重态能量转移效率（92.8%）和显著长的发射体三重态寿命（17.8 ms），它们分别反映了高发射体浓度和刚性发色团环境。本体透明上转换树脂可以在空气中制备并在空气中发挥作用，这为广泛的实际应用开辟了一条新途径。
