Injection Kinetics and Electronic Structure at the N719/TiO2 Interface Studied by Means of Ultrafast XUV Photoemission Spectroscopy,The Journal of Physical Chemistry C

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Injection Kinetics and Electronic Structure at the N719/TiO2 Interface Studied by Means of Ultrafast XUV Photoemission Spectroscopy
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2015-04-17 00:00:00 , DOI: 10.1021/acs.jpcc.5b01216
Mario Borgwardt ₁ , Martin Wilke ₁ , Thorsten Kampen ₂ , Sven Mähl ₂ , Wanchun Xiang _{3,

4} , Leone Spiccia ₃ , Kathrin M. Lange ₅ , Igor Yu. Kiyan ₁ , Emad F. Aziz _{1,

6}

Affiliation

The method of transient XUV photoemission spectroscopy is developed to investigate the ultrafast dynamics of heterogeneous electron transfer at the interface between the N719 ruthenium dye complex and TiO₂ nanoparticles. XUV light from high-order harmonic generation is used to probe the electron density distribution among the ground and excited states at the interface after its exposure to a pump laser pulse of 530 nm wavelength. A spectral decomposition of the transient emission signal is used to follow the population and decay dynamics of the involved transient states individually. By comparing results obtained for the N719/TiO₂ and N719/FTO interfaces, we can unambiguously reveal the kinetics of electrons injected to TiO₂ from the singlet metal-to-ligand charge-transfer (MLCT) excited state of the dye. With the developed approach, we characterize both the kinetic constants and the absolute binding energies of the singlet and triplet MLCT states of the dye and the state of electrons injected to the conduction band of TiO₂. The energy levels of the singlet and triplet states are found to lie 0.7 eV above and 0.2 eV below the conduction band minimum, respectively. This energetic structure gives rise to a strong driving force for injection from the singlet state and a slow electron transfer from the triplet state, the latter being possible due to a partial overlap of the triplet state band of N719 and the conduction band of TiO₂.

中文翻译：

超快XUV光发射光谱法研究N719 / TiO ₂界面的注入动力学和电子结构

开发了瞬态XUV光发射光谱法，以研究N719钌染料配合物与TiO ₂纳米粒子之间界面的异质电子转移的超快动力学。来自高次谐波产生的XUV光在暴露于530 nm波长的泵浦激光脉冲后，用于探测界面处基态和激发态之间的电子密度分布。瞬态发射信号的频谱分解用于分别跟踪所涉及的瞬态的数量和衰减动力学。通过比较从N719 / TiO ₂和N719 / FTO界面获得的结果，我们可以清楚地揭示注入TiO ₂的电子的动力学从单重态金属到配体电荷转移（MLCT）的染料激发态。使用已开发的方法，我们既可以表征染料的单重态和三重态MLCT状态的动力学常数和绝对结合能，也可以表征注入TiO ₂导带的电子状态。发现单重态和三重态的能级分别位于导带最小值之下0.7 eV和之下0.2 eV。这种高能结构从单重态起注入有很强的驱动力，而从三重态起电子转移较慢，这是由于N719的三重态能带和TiO ₂的导带部分重叠造成的。

更新日期：2015-04-17

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