The understanding of the dissociation dynamics of charge transfer excitons at organic donor-acceptor interfaces is critical for designing organic photovoltaics. One of the strategies to split the charge transfer exciton and to avoid electron-hole recombination is by using an energy cascade structure. In these cascade structures, electron and hole are funneled into two different layers that are spatially separated. Previous studies have shown that fast exciton dissociation can occur at the ZnPc/PTCDA interface. In this study, we insert an interlayer, F8ZnPc, between the ZnPc and PTCDA layers. The F8ZnPc has HOMO and LUMO levels that are sandwiched between those of ZnPc and PTCDA. By varying the thickness of the intermediate F8ZnPc layer above and below the exciton delocalization size, we investigate the feasibility of funneling electrons and holes into the PTCDA and the ZnPc layers, respectively, via ultrafast coherent transport. The temperature dependence of the charge separation yield and dynamics are measured and compared to that of the bilayer ZnPc/PTCDA sample.

Using an energy cascade trilayer structure to dissociate photoexcited excitons at organic semiconductor interfaces

ACS Spring Meeting 2021

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