Maximizing the efficiency of solar energy conversion using dye assemblies rests on understanding where the energy goes following absorption. Transient spectroscopies in solution are useful for this purpose, and the time-resolved data are usually analyzed with a sum of exponentials. This treatment assumes that dynamic events are well separated in time, and that the resulting exponential prefactors and phenomenological lifetimes are related directly to primary physical values. Such assumptions break down for coincident absorption, emission, and excited state relaxation that occur in transient absorption and photoluminescence of tris(2,2′-bipyridine)ruthenium(2+) derivatives, confounding the physical meaning of the reported lifetimes. In this work, we use inductive modeling and stochastic chemical kinetics to develop a detailed description of the primary ultrafast photophysics in transient spectroscopies of a series of Ru dyes, as an alternative to sums of exponential analysis. Commonly invoked three-level schemes involving absorption, intersystem crossing (ISC), and slow nonradiative relaxation and incoherent emission to the ground state cannot reproduce the experimentally measured spectra. The kinetics simulations reveal that ultrafast decay from the singlet excited state manifold to the ground state competes with ISC to the triplet excited state, whose efficiency was determined to be less than unity. The populations predicted by the simulations are used to estimate the magnitudes of transition dipoles for excited state excitations and evaluate the influence of specific ligands. The mechanistic framework and methodology presented here are entirely general, applicable to other dye classes, and can be extended to include charge injection by molecules bound to semiconductor surfaces.

中文翻译：

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通过随机动力学模拟确定的钌多吡啶基发色团的超快弛豫。

使用染料组件使太阳能转换效率最大化取决于理解吸收后能量的流向。溶液中的瞬态光谱仪可用于此目的，通常使用指数总和分析时间分辨数据。这种处理方法假定动态事件在时间上间隔良好，并且所得的指数前因子和现象学寿命与主要物理值直接相关。这些假设打破了三（2,2'-联吡啶）钌（2+）衍生物在瞬态吸收和光致发光中同时发生的吸收，发射和激发态弛豫，从而混淆了所报告寿命的物理意义。在这项工作中 我们使用归纳建模和随机化学动力学方法，对一系列Ru染料的瞬态光谱中的主要超快光物理进行了详细描述，以替代指数分析总和。涉及吸收，系统间穿越（ISC）以及缓慢的非辐射弛豫和向基态的非相干发射的通常调用的三级方案无法重现实验测量的光谱。动力学模拟表明，从单重激发态流形到基态的超快衰减与ISC竞争到三重激发态，三重激发态的效率被确定为小于1。通过模拟预测的总体可用于估算激发态激发的跃迁偶极子的大小，并评估特定配体的影响。