Femtosecond Fluorescence Upconversion Study of a Naphthalimide–Bithiophene–Triphenylamine Push–Pull Dye in Solution,The Journal of Physical Chemistry A

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Femtosecond Fluorescence Upconversion Study of a Naphthalimide–Bithiophene–Triphenylamine Push–Pull Dye in Solution
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2018-06-01 00:00:00 , DOI: 10.1021/acs.jpca.8b05177
Valentin Maffeis _{1,

2} , Romain Brisse ₂ , Vanessa Labet ₃ , Bruno Jousselme ₂ , Thomas Gustavsson ₁

Affiliation

There is a high interest in the development of new push–pull dyes for the use in dye sensitized solar cells. The pronounced charge transfer character of the directly photoexcited state is in principle favorable for a charge injection. Here, we report a time-resolved fluorescence study of a triphenylamine–bithiophene–naphthalimide dye in four solvents of varying polarity using fluorescence upconversion. The recording of femtosecond time-resolved fluorescence spectra corrected for the group velocity dispersion allows for a detailed analysis discriminating between spectral shifts and total intensity decays. After photoexcitation, the directly populated state (S₁/FC) evolves toward a relaxed charge transfer state (S₁/CT). This S₁/CT state is characterized by a lower radiative transition moment and a higher nonradiative quenching. The fast dynamic shift of the fluorescence band is well described by solvation dynamics in polar solvents, but less so in nonpolar solvents, hinting that the excited-state relaxation process occurs on a free energy surface whose topology is strongly governed by the solvent polarity. This study underlines the influence of the environment on the intramolecular charge transfer (ICT) process, and the necessity to analyze time-resolved data in detail when solvation and ICT occur simultaneously.

中文翻译：

溶液中萘二甲酰亚胺-联噻吩-三苯胺推挽染料的飞秒荧光上转换研究

人们对用于染料敏化太阳能电池的新型推挽式染料的开发非常感兴趣。直接光激发态的明显的电荷转移特性原则上有利于电荷注入。在这里，我们报告了使用荧光上转换技术在四种极性不同的溶剂中对三苯胺-联噻吩-萘二甲酰亚胺染料进行的时间分辨荧光研究。飞秒时间分辨荧光光谱的记录已针对群速度色散进行了校正，从而可以进行详细的分析，从而区分光谱偏移和总强度衰减。在光激发之后，直接填充的状态（S ₁ / FC）向松弛的电荷转移状态（S ₁ / CT）发展。这个S ₁/ CT状态的特征在于较低的辐射跃迁矩和较高的非辐射猝灭。荧光带的快速动态移动可以通过极性溶剂中的溶剂化动力学很好地描述，而在非极性溶剂中则更少，这表明激发态松弛过程发生在自由能表面上，该自由能表面的拓扑结构主要受溶剂极性控制。这项研究强调了环境对分子内电荷转移（ICT）过程的影响，以及在同时发生溶剂化和ICT时详细分析时间分辨数据的必要性。

更新日期：2018-06-01

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