连续波与脉冲激光器在三重态-三重态湮灭上转换中的应用(特邀)

Application of continuous wave and pulsed lasers in triplet-triplet annihilation upconversion(Invited)

三重态-三重态湮灭上转换是一种新型光子上转换技术,具有使用连续波光源激发、上转换波长灵活可调和上转换量子效率高等优点。在该上转换过程中,三重态光敏剂吸收激发光、发生系间窜越并作为三重态能量给体,通过三重态能量转移过程,敏化能量受体,处于三重态的受体分子发生三重态–三重态湮灭,产生能发生高效荧光过程的单重激发态(即上转换发光),从而将低能量的光子转换为高能量的光子,这为提高太阳能电池的光电转换效率或光催化的效率等,提供了一种新的途径。实验中需要选用合适的激光器激发上转换体系产生上转换发光,并研究其具体光物理过程。如选用连续波二极管泵浦固体激光器(DPSSL)作为光源,激发光敏剂/受体体系进行上转换实验,可方便地研究激光功率密度对上转换发光效率的影响。此外,为了研究上转换发光的动力学过程,使用光学参量振荡器(OPO)可调谐纳秒脉冲激光器激发上转换体系,可以研究光敏剂的三重态寿命、分子间能量转移以及三重态–三重态湮灭等过程的动力学特征。文中介绍了在三重态–三重态湮灭上转换实验中连续波和脉冲激光器的使用方法。

The triplet-triplet annihilation upconversion is a new technology for photonic upconversion,which has the advantages such as continuous wave excitation,tunable upconversion wavelength and high upconversion quantum yields.In this upconversion process,as the energy donor,photosensitizer absorbs the light excitation,and intersystem crossing occurs,then sensitizes the energy acceptor through the triplet-triplet energy transfer process.Finally,the triplet-triplet annihilation of the energy acceptor in the triplet state generates a single excited state which can produce high-efficiency fluorescence(i.e.upconversion luminescence),thus the low-energy light is converted into higher-energy upconversion luminescence,which provides a feasible method for improving the photoelectric conversion efficiency of solar cells or the efficiency of photocatalysis,etc.It is desired to select appropriate lasers to excite the photosensitizer/energy donor system to study the steady upconversion luminescence and the upconversion kinetics.For instance,continuous wave diode pumped solid state laser(DPSSL)was selected as the light source to excite photosensitizer/acceptor system,upconversion luminescence was observed,and the effect of laser power density on upconversion luminescence can be studied conveniently.Additionally,in order to analyze the kinetic process of upconversion luminescence,with optical parametric oscillator(OPO)tunable pulsed laser as the light source,the lifetime of the triplet state,the kinetic characteristics of intermolecular energy transfer and triplet annihilation of photosensitizers can be studied.The application of continuous wave and pulse lasers in triplet–triplet annihilation upconversion experiments was introduced.