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为了实现窄能隙有机光敏剂的理性设计,有必要全面理解发生在二氧化钛/染料/电解质复杂界面的激发态演化动力学。本文通过构建分别以苯并噻二唑-苯甲酸(BTBA)和吡啶并噻二唑-苯甲酸(PTBA)为电子受体的有机给受体染料,借助超快瞬态吸收光谱测量与理论模拟,我们发现在实际的二氧化钛/染料/电解质界面存在激发态多步弛豫与多态电子注入的过程。密度泛函理论及含时密度泛函理论计算表明,二氧化钛表面的光激发产生的“热”激发态染料分子会通过分子片段间的扭转运动发生显著的多步结构弛豫,最终形成共轭骨架具有醌式结构、更加平面化的平衡构型。通过对飞秒瞬态吸收光谱进行目标分析,我们发现相对于以苯并噻二唑-苯甲酸为电子受体的染料,以吡啶并噻二唑-苯甲酸为电子受体的染料呈现出较慢的电子注入速率与较短的激发态寿命,导致总的电子注入产率较低,给出了基于该染料所制备的太阳电池的外量子产率峰值低的原因。
In order to achieve the rational design of narrow bandgap organic photosensitizers, it is necessary to fully understand the evolution dynamics of the excited states occurring at the titanium dioxide / dye / electrolyte complex interface. In this paper, the organic dye acceptor dyes with benzothiadiazole-benzoic acid (BTBA) and pyridylthiadiazole-benzoic acid (PTBA) as electron acceptor were synthesized and characterized by means of ultrafast transient absorption spectroscopy and theoretical simulation , We find that there is an excited state multi-step relaxation and polymorphic electron injection at the actual titania / dye / electrolyte interface. Density functional theory and time-dependent density functional theory calculations show that the “hot” excited-state dye molecules generated by the photo-excitation of titanium dioxide surface undergo significant multistage structure relaxation through the torsional movement between molecular fragments, The yoke skeleton has a quinoid structure, a more planar equilibrium configuration. Through the target analysis of the transient absorption spectra of femtosecond, we found that compared with the benzothiadiazole-benzoic acid dye as electron acceptor, the dyes with pyridothiadiazole-benzoic acid as electron acceptor showed a better performance The slow electron injection rate and shorter lifetime of the excited state result in a lower total electron injection yield, giving the reason that the peak of the external quantum yield of the solar cell prepared on the basis of this dye is low.