Murakami Yoichi, Das Sudhir Kumar, Himuro Yuki, Maeda Satoshi
School of Engineering, Tokyo Institute of Technology, 2-12-1-I1-15 Ookayama, Meguro-ku, Tokyo 152-8552, Japan.
Phys Chem Chem Phys. 2017 Nov 22;19(45):30603-30615. doi: 10.1039/c7cp06494b.
Photon upconversion (UC) is a technology that can increase solar utilization efficiencies in broad photoenergy conversion systems by converting lower-energy photons into usable higher-energy photons. Recently, UC using triplet-triplet annihilation (TTA) of organic molecules has drawn attention because it is presently the only method applicable to weak and noncoherent light. To date, many attempts have been made to realize this UC technology in forms suitable for applications, but they typically suffer from either high cost or insufficient stability and/or safety of materials. Recently, a new class of liquid called deep eutectic solvents (DESs) has emerged as low-cost green fluids that possess low toxicity and vapor pressure, biodegradability, and high thermal stability. DESs have been proposed as an alternative to ionic liquids. This article develops triplet-sensitized UC samples using DESs that are found to be suitable solvents for this purpose, attaining a new materials platform for UC with the aforementioned advantages. The high thermal stability of the samples is qualitatively confirmed and their UC quantum yields are determined to be 0.11-0.21 (based on the definition that the maximum quantum yield is 0.5) depending on the DES composition. The triplet lifetime of the emitter 9,10-diphenylanthracene increases with DES viscosity, resulting in unique kinetics. Analysis of photophysical experimental results allows the relevant physics governing the performance of this sample system to be determined and discussed. Overall, a novel UC platform that simultaneously achieves high thermal stability, low cost, and environmental friendliness is developed using DESs as the solvent.
光子上转换（UC）是一种可通过将低能量光子转换为可用的高能量光子来提高广泛光能量转换系统中太阳能利用效率的技术。最近，利用有机分子的三重态-三重态湮灭（TTA）进行的UC引起了关注，因为它是目前唯一适用于弱光和非相干光的方法。迄今为止，人们已进行了许多尝试，以实现适用于实际应用的这种UC技术，但它们通常要么成本高昂，要么材料的稳定性和/或安全性不足。最近，一类名为深共熔溶剂（DESs）的新型液体作为低成本绿色流体出现了，它们具有低毒性、低蒸气压、生物可降解性和高热稳定性。DESs已被提议作为离子液体的替代品。本文开发了使用DESs的三重态敏化UC样品，发现它们是适用于此目的的溶剂，从而获得了具有上述优点的UC新材料平台。定性确认了样品的高热稳定性，并根据DES组成确定其UC量子产率为0.11 - 0.21（基于最大量子产率为0.5的定义）。发射体9,10 - 二苯基蒽的三重态寿命随DES粘度增加，导致独特的动力学。对光物理实验结果的分析有助于确定和讨论控制该样品系统性能的相关物理原理。总体而言，以DESs作为溶剂开发了一种同时实现高热稳定性、低成本和环境友好性的新型UC平台。
