Role of coherence and delocalization in photo-induced electron transfer at organic interfaces.
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.
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.
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Abramavicius
Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania.
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Pranculis
Biomolecular and Organic Electronics, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.
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Melianas
Biomolecular and Organic Electronics, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.
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Inganäs
Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania.
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Gulbinas
Vilnius University, Faculty of Physics, Department of Theoretical Physics, Saulėtekio 9, LT-10222 Vilnius Lithuania.
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Abramavicius