Simulations of Frenkel to Wannier–Mott Exciton Transitions in a Nanohybrid System,The Journal of Physical Chemistry C

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Simulations of Frenkel to Wannier–Mott Exciton Transitions in a Nanohybrid System
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-11-29 , DOI: 10.1021/acs.jpcc.8b09697
Thomas Plehn ₁ , Dirk Ziemann ₁ , Volkhard May ₁

Affiliation

Excitation energy transfer at a prototypical organic/inorganic interface is described theoretically. The nanohybrid system to be investigated is built up by a vertical stacking of 20 para-sexiphenyl molecules physisorbed on a ZnO nanocrystal of 3903 atoms. To determine the time scale of excitation energy transfer all relevant electronic excitations of the organic and inorganic part are computed together with the related excitation energy transfer couplings. Values of the coupling lie in the millielectronvolt range or less. This motivates a Golden Rule description of the excitation energy transfer. Different Frenkel excitons are chosen as excitation energy donor levels. Due to the H-aggregate configuration of the organic part, the number of exciton wave function nodes increases with decreasing exciton energy. As a result, the couplings of the individual molecules to a certain ZnO electron–hole pair cancel each other more intensively and the overall transfer rate gets smaller. The highest exciton levels decay most rapidly and are characterized by lifetimes in the picosecond region. The lower part of the exciton band, however, has lifetimes in the nanosecond region. The Golden Rule description is finally compared to a direct solution of the time-dependent Schrödinger equation. The obtained transfer dynamics confirm those of the rate equation approach when the higher part of the Frenkel exciton band is considered. In the lower part, the reduced number of final electron–hole pair states in the inorganic part blocks the Frenkel exciton decay.

中文翻译：

纳米杂化系统中Frenkel到Wannier-Mott激子跃迁的模拟

理论上描述了在原型有机/无机界面上的激发能转移。待研究的纳米杂化系统是由20的垂直叠加建立了对-联苯并苯基分子物理吸附在3903个原子的ZnO纳米晶体上。为了确定激发能传递的时间尺度，将有机和无机部分的所有相关电子激发与相关的激发能传递耦合一起进行计算。耦合的值在毫伏或以下。这激发了激励能量转移的黄金法则描述。选择不同的Frenkel激子作为激发能供体能级。由于有机部分的H聚集构型，激子波函数节点的数量随着激子能量的减少而增加。结果，单个分子与某个ZnO电子-空穴对的偶联会更强烈地相互抵消，并且总转移速率会变小。最高激子能级衰减最快，其特征在于皮秒区的寿命。然而，激子带的下部具有纳秒级的寿命。最后，将黄金法则描述与时间相关的Schrödinger方程的直接解进行比较。当考虑Frenkel激子带的较高部分时，获得的传递动力学证实了速率方程方法的动力学。在下部，无机部分中最终的电子-空穴对态数量的减少阻止了Frenkel激子的衰减。当考虑Frenkel激子带的较高部分时，获得的传递动力学证实了速率方程方法的动力学。在下部，无机部分中最终的电子-空穴对态数量的减少阻止了Frenkel激子的衰减。当考虑Frenkel激子带的较高部分时，获得的传递动力学证实了速率方程方法的动力学。在下部，无机部分中最终的电子-空穴对态数量的减少阻止了Frenkel激子的衰减。

更新日期：2018-11-29

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