KEYWORDS: Modeling and simulation, Solar energy, Proteins, Control systems, Systems modeling, Spectroscopy, Picosecond phenomena, Photovoltaics, Photosynthesis, Microwave radiation
Biological systems involved in photosynthesis have recently revealed nanoscale properties and robust quantum behavior, exhibiting photon-to-electron conversion efficiency close to one. Today it is believed that this record is offered by the assistance of the interaction with the vibrations of the surrounding protein scaffold.
In this contribution, we propose to discuss potential technological alternative for mimicking such a synergistic mechanism, in a biologically-inspired two-branch molecular junction. We demonstrate that time-dependent external excitations may enhance the photocurrent inside the junction.
During the primary steps of photosynthesis, the light-harvesting complexes capture sunlight and transfer the associated energy to reaction centers where charge are separated. Surprisingly, optical spectroscopy has recently revealed manifestations of quantum coherence in the ultrafast dynamics of these natural nanosystems, that would be controlled by the interaction between excitations and the surrounding protein motion. Inspired by the architecture of a natural reaction center, we have designed a generic molecular nanodevice, and simulated the time-dependent photocurrent induced by a femtosecond laser pulse. In this analogue, a time-dependent external voltage is applied to the device in the picosecond timescale via a gate, in order to mimic the effects of protein vibrations. The voltage characteristics are the parameters of this study. The numerical investigation we propose aims at unraveling the conditions in which this external control may increase the photocurrent inside the nanodevice. To this aim, we have developed a combined theoretical/numerical framework to describe and understand the quantum transport of energy and charges, from the nonequilibrium Green's function formalism. Our findings show that such an external control may be beneficial for the integrated (dc) current owing through the interface. Indeed, this external control enables to prevent the back tunneling oscillations of the timedependent photocurrent, which globally enhances the dc current. This exploratory work paves the way towards smart biologically-inspired optoelectronics.
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