低能量的光子转化成高能量光子的过程被称为光子频率上转换，可以通过多光子吸收、参量过程、二次谐波或三线态-三线态湮灭(TTA)等方式实现。TTA上转换不仅可使用非相干的弱光源激发来实现，有机分子的使用还可以方便地调节转换波长并有效提高上转换的总体效率。本课题的目标是通过选择合适发色团和“能量库”，结合能量传递平衡态策略，设计长激发态寿命的敏化剂，促进分子间的三线态-三线态能量传递，从而提高TTA上转换的效率。拟采用三环金属化铱(III)配合物为核心敏化剂，叔丁基芘为“能量库”延长敏化剂的激发态寿命。同时，叔丁基芘还是光稳定的湮灭剂，因此我们提出“湮灭剂共价修饰敏化剂”可以增强TTA上转换效率。本项目的成功实施可以获得一系列长磷光寿命的有机光敏化剂，提高所涉及的光子上转换效率；为TTA上转换提供一种通用的“湮灭剂共价修饰敏化剂”策略；该类敏化剂还可用于氧气传感、单线态氧敏化、光化学催化等领域。

The generation of higher energy photons excited by lower energy photons is known as photon upconversion. The general mechanisms for photon upconversion are mainly multi-photon absorption, parametric processes, second harmonic generation, and triplet-triplet annihilation (TTA). Photon upconversion based on TTA can be realized under non-coherent low power (mW•cm-2) light source. Moreover, the usage of organic molecules allows easy adjustment of excitation and emission wavelength and enhances the overall upconversion efficiency. In this project, we aims to design long excited state lifetime photosensitizers by fabricating suitable organic chromophore and “energy reservoir” according to reversible electronic energy transfer strategy. The novel sensitizers can accelerate intermolecular triplet triplet energy transfer and improve the TTA upconversion efficiency. We plan to adopt 2,7-di-tert-butylpyrene (DBP) as “energy reservoir” to prolong the excited state lifetime of tris(cyclometalated) iridium(III) complex which will be used as core sensitizers. As DBP is also a photo stable annihilator, we also propose that “annihilator appended sensitizers” strategy can enhance the TTA upconversion efficiency. This project will have the following expected achievements: 1) to obtain a series of organic photosensitizers with long phosphorescence lifetimes and improve the efficiency of TTA upconversion; 2) to provide the general strategy of “annihilator appended sensitizers” for the TTA upconversion; 3) to apply these sensitizers as oxygen sensors, singlet oxygen sensitizers, photochemical catalysts, etc.