Photon upconversion based on nonlinear processes such as two-photon absorption (TPA) and triplet–triplet annihilation (TTA) has attracted a great amount of attention with the aim of manipulating the photon energy in various fields. Cascading these two processes (TPA and TTA) allows a large anti-Stokes shift; however, a rational design of organic sensitizers has been so far unexplored. Here we report amino (−NH₂)- or carboxyl (−COOH)-appended platinum(II) tetraphenylporphyrin (PtTPP) molecules that are intended to coordinate a CsPbBr₃ perovskite quantum dot (PQD) and render an increased spectrum overlap between the photoabsorption of PtTPP and the photoemission from PQD. These TPP molecules exhibit higher energy transfer yields than a reference porphyrin (platinum octaethylporphyrin: PtOEP) via static quenching and mediate the following TTA process of diphenylanthracene (DPA). The resultant power factor in the excitation density dependence (an 800 nm femtosecond pulse) is the highest for tetracarboxyl-appended TPP, accompanying a distinct emission from the DPA singlet excited state. This study brings out the importance of tailoring the photophysical and coordinative properties of the sensitizers in the TPA-TTA cascade process.

中文翻译：

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NH ₂或COOH附加的Pt-卟啉与CsPbBr ₃钙钛矿量子点的配位，以改善双光子吸收和三重态-三重An灭的级联过程

基于非线性过程（例如双光子吸收（TPA）和三重态-三重态三态an灭（TTA））的光子上转换已经引起了人们的广泛关注，目的是在各个领域中操纵光子能量。级联这两个过程（TPA和TTA）可以实现较大的反斯托克斯位移；然而，迄今为止尚未探索有机敏化剂的合理设计。在这里我们报告氨基（-NH ₂）-或羧基（-COOH）附加的铂（II）四苯基卟啉（PtTPP）分子，旨在协调CsPbBr ₃钙钛矿量子点（PQD），并在PtTPP的光吸收和PQD的光发射之间产生增加的光谱重叠。这些TPP分子通过静态猝灭显示出比参考卟啉（八乙基卟啉铂：PtOEP）更高的能量转移产率，并介导了随后的二苯基蒽（DPA）的TTA过程。激发密度依赖性（800 nm飞秒脉冲）的合成功率因数对于四羧基键合的TPP最高，伴随着DPA单线态激发态的明显发射。这项研究提出了在TPA-TTA级联过程中调整敏化剂的光物理和配位性质的重要性。