Charge transfer (CT) is an essential phenomenon relevant to numerous fields including biology, physics and chemistry.1-5 Here, we demonstrate that multi-layered hyperbolic metamaterial (HMM) substrates alter organic semiconductor CT dynamics.6 With triphenylene:perylene diimide dyad supramolecular self-assemblies prepared on HMM substrates, we show that both charge separation (CS) and charge recombination (CR) characteristic times are increased by factors of 2.5 and 1.6, respectively, resulting in longer-lived CT states. We successfully rationalize the experimental data by extending Marcus theory framework with dipole image interactions tuning the driving force. The number of metal-dielectric pairs alters the HMM interfacial effective dielectric constant and becomes a solid analogue to solvent polarizability. Based on the experimental results and extended Marcus theory framework, we find that CS and CR processes are located in normal and inverted regions on Marcus parabola diagram, respectively. The model and further PH3T:PCBM data show that the phenomenon is general and that molecular and substrate engineering offer a wide range of kinetic tailoring opportunities. This work opens the path toward novel artificial substrates designed to control CT dynamics with potential applications in fields including optoelectronics, organic solar cells and chemistry.
1. Marcus, Rev. Mod. Phys., 1993, 65, 599.
2. Marcus, Phys. Chem. Chem. Phys., 2012, 14, 13729.
3. Lambert, et al., Nat. Phys., 2012, 9, 10.
4. C. Clavero, Nat. Photon., 2014, 8, 95.
5. A. Canaguier-Durand, et al., Angew. Chem. Int. Ed., 2013, 52, 10533.
6. K. J. Lee, et al., Submitted, 2015, arxiv.org/abs/1510.08574.
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