Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700, Fribourg, Switzerland.
Dipartimento di Scienza dei Materiali, Università of Milano-Bicocca, Via Cozzi 55, I-20125, Milano, Italy.
Adv Mater. 2017 Nov;29(41). doi: 10.1002/adma.201702992. Epub 2017 Sep 12.
Sensitized triplet-triplet-annihilation-based photon upconversion (TTA-UC) permits the conversion of light into radiation of higher energy and involves a sequence of photophysical processes between two dyes. In contrast to other upconversion schemes, TTA-UC allows the frequency shifting of low-intensity light, which makes it particularly suitable for solar-energy harvesting technologies. High upconversion yields can be observed for low viscosity solutions of dyes; but, in solid materials, which are better suited for integration in devices, the process is usually less efficient. Here, it is shown that this problem can be solved by using transparent nanodroplet-containing polymers that consist of a continuous polymer matrix and a dispersed liquid phase containing the upconverting dyes. These materials can be accessed by a simple one-step procedure that involves the free-radical polymerization of a microemulsion of hydrophilic monomers, a lipophilic solvent, the upconverting dyes, and a surfactant. Several glassy and rubbery materials are explored and a range of dyes that enable TTA-UC in different spectral regions are utilized. The materials display upconversion efficiencies of up to ≈15%, approaching the performance of optimized oxygen-free reference solutions. The data suggest that the matrix not only serves as mechanically coherent carrier for the upconverting liquid phase, but also provides good protection from atmospheric oxygen.
敏化三重态-三重态湮灭上转换（TTA-UC）允许光转换为更高能量的辐射，并涉及两种染料之间的一系列光物理过程。与其他上转换方案相比，TTA-UC 允许低强度光的频率移动，这使其特别适用于太阳能收集技术。在染料的低粘度溶液中可以观察到高的上转换产率；但是，在更适合集成在器件中的固体材料中，该过程通常效率较低。在这里，通过使用包含上转换染料的透明纳米液滴聚合物来解决这个问题，这些聚合物由连续的聚合物基质和包含上转换染料的分散液相组成。这些材料可以通过简单的一步程序来获得，该程序涉及亲水性单体、亲脂性溶剂、上转换染料和表面活性剂的微乳液的自由基聚合。探索了几种玻璃态和橡胶态材料，并利用了能够在不同光谱区域实现 TTA-UC 的一系列染料。这些材料的上转换效率高达约 15%，接近优化的无氧参考溶液的性能。数据表明，该基质不仅作为上转换液相的机械上连贯载体，而且还提供了对大气氧的良好保护。
