Sakamoto Souichi, Tanimura Yoshitaka
Department of Chemistry, Graduate School of Science, Kyoto University , Sakyoku, Kyoto 606-8502, Japan.
J Phys Chem Lett. 2017 Nov 2;8(21):5390-5394. doi: 10.1021/acs.jpclett.7b01535. Epub 2017 Oct 23.
We theoretically investigate an exciton-coupled electron transfer (XCET) process that is conversion of an exciton into a charge transfer state. This conversion happens in an exciton transfer (XT) process, and the electron moves away in an electron transfer (ET) process in multiple environments (baths). This XCET process plays an essential role in the harvesting of solar energy in biological and photovoltaic materials. We develop a practical theoretical model to study the efficiency of the XCET process that occurs either in consecutive or concerted processes under the influence of non-Markovian baths. The role of quantum coherence in the XT-ET system and the baths is investigated using reduced hierarchal equations of motion (HEOM). This model includes independent baths for each XT and ET state, in addition to a XCET bath for the conversion process. We found that, while quantum system-bath coherence is important in the XT and ET processes, coherence between the XT and ET processes must be suppressed in order to realize that an efficient irreversible XCET process through the weak off-diagonal interaction between the XT and ET bridge sites arises from an XCET bath.
我们从理论上研究了一种激子耦合电子转移（XCET）过程，即激子转化为电荷转移态的过程。这种转化发生在激子转移（XT）过程中，并且电子在多个环境（浴）中的电子转移（ET）过程中离开。这种XCET过程在生物和光伏材料的太阳能收集过程中起着至关重要的作用。我们开发了一个实用的理论模型，以研究在非马尔可夫浴影响下，连续或协同过程中发生的XCET过程的效率。使用约化运动层次方程（HEOM）研究了量子相干在XT - ET系统和浴中的作用。该模型除了用于转化过程的XCET浴外，还包括每个XT和ET态的独立浴。我们发现，虽然量子系统 - 浴相干在XT和ET过程中很重要，但为了实现通过XT和ET桥位之间的弱非对角相互作用产生的高效不可逆XCET过程，必须抑制XT和ET过程之间的相干性，这种相互作用源于XCET浴。
