Vilnius University, Faculty of Physics, Department of Theoretical Physics, Saulėtekio 9, LT-10222 Vilnius Lithuania.
Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania.
Sci Rep. 2016 Sep 8;6:32914. doi: 10.1038/srep32914.
Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.
由于基于电子给体和受体材料混合物的有机太阳能电池（OSC）的发展，分子异质结的光致电荷转移引起了特别的关注。虽然可以用马库斯理论来描述给体和受体分子之间的电荷转移，但额外的载流子离域和相干传播可能起着主导作用。在这里，我们使用随机薛定谔方程（SSE）描述了共轭聚合物和富勒烯衍生物 PCBM 聚集体界面处的超快电荷分离，并揭示了电子相干和离域介导的电子转移的复杂时间演化。通过将模型拟合到超快电荷分离实验中，我们估计了电子离域的程度，并确定了从相干电子输运到非相干跳跃的转变。我们的结果表明，即使 PCBM 分子之间的耦合相对较弱，也足以促进有机界面处的电子离域和有效的电荷分离。
