Photon upconversion based on sensitized triplet–triplet annihilation in bi-component systems is a multistep process that involves a triplet–triplet energy transfer (ET) from a donor to an acceptor moiety. This is aimed at sensitizing the population of annihilating optically dark triplets that generates the high energy photoluminescence. A large resonance between the involved triplets is usually recommended because it increases the energy gain between absorbed and emitted upconverted photons. However, it also enables efficient back-ET from acceptor to donor triplets, with potential detrimental consequences on the system performance. Here, we analyze a model system, where the energy difference between donor and acceptor triplets is lower than k_BT at room temperature by means of time resolved and steady state photoluminescence spectroscopy, and develop a kinetic model, which describes the iterative loop that transfers the triplet exciton between the donor and acceptor molecules. In such a way, we obtained the guidelines for the optimization of the system composition required to overcome the back-ET effect and maximize the upconversion quantum yield.

中文翻译：

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多组分系统中的光子上转换：反向能量转移的作用。

基于双组分系统中敏化三重态-三重态let灭的光子上转换是一个多步过程，涉及从供体到受体部分的三重态-三重态能量转移（ET）。这旨在使产生高能光致发光的optical灭光学暗三重态的群体敏感。通常建议在三胞胎之间引起较大的共振，因为这会增加吸收和发射的上转换光子之间的能量增益。但是，它还可以实现从受体到供体三联体的高效反向ET，从而对系统性能产生潜在的有害影响。在这里，我们分析一个模型系统，其中供体和受体三重态之间的能量差低于k _B T在室温下通过时间分辨和稳态光致发光光谱法研究并建立动力学模型，该动力学模型描述了在供体和受体分子之间转移三重态激子的迭代回路。通过这种方式，我们获得了克服逆向ET效应并最大化上转换量子产率所需的系统组成优化指南。