Institut für Physik, Carl von Ossietzky Universität, 26129 Oldenburg, Germany. Center of Interface Science, Carl von Ossietzky Universität, 26129 Oldenburg, Germany.
Istituto Nanoscienze-Consiglio Nazionale delle Ricerche (CNR), Centro S3, via Campi 213a, 41125 Modena, Italy.
Science. 2014 May 30;344(6187):1001-5. doi: 10.1126/science.1249771.
Blends of conjugated polymers and fullerene derivatives are prototype systems for organic photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, we elucidate the initial quantum dynamics of this process. Experimentally, we observed coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with first-principle theoretical simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-femtosecond period matching that of the observed vibrational modes. Our results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound reference system.
共轭聚合物和富勒烯衍生物的混合物是有机光伏器件的典型体系。主要的电荷产生机制涉及光诱导的超快电子从光吸收和供电子聚合物到富勒烯电子受体的转移。在这里，我们阐明了这个过程的初始量子动力学。实验上，我们在聚合物给体的光脉冲激发后观察到富勒烯部分的相干振动运动。与第一性原理理论模拟的比较证明了给体和受体之间的相干电子转移以及转移电荷的振荡，其 25 飞秒的周期与观察到的振动模式相匹配。我们的结果表明，电子和核自由度之间的相干电子耦合对于在非共价键合的参考体系中引发电荷离域和转移至关重要。
