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The molecular photo-cell: quantum transport and energy conversion at strong non-equilibrium.

Ajisaka S, Žunkovič B, Dubi Y - Sci Rep (2015)

Bottom Line: The molecular photo-cell is a single molecular donor-acceptor complex attached to electrodes and subject to external illumination.Moreover, this system includes electrons, phonons and photons, and environments which induce coherent and incoherent processes, making it a challenging system to address theoretically.Here, using an open quantum systems approach, we analyze the non-equilibrium transport properties and energy conversion performance of a molecular photo-cell, including both coherent and incoherent processes and treating electrons, photons, and phonons on an equal footing.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.

ABSTRACT
The molecular photo-cell is a single molecular donor-acceptor complex attached to electrodes and subject to external illumination. Besides the obvious relevance to molecular photo-voltaics, the molecular photo-cell is of interest being a paradigmatic example for a system that inherently operates in out-of-equilibrium conditions and typically far from the linear response regime. Moreover, this system includes electrons, phonons and photons, and environments which induce coherent and incoherent processes, making it a challenging system to address theoretically. Here, using an open quantum systems approach, we analyze the non-equilibrium transport properties and energy conversion performance of a molecular photo-cell, including both coherent and incoherent processes and treating electrons, photons, and phonons on an equal footing. We find that both the non-equilibrium conditions and decoherence play a crucial role in determining the performance of the photovoltaic conversion and the optimal energy configuration of the molecular system.

No MeSH data available.


Related in: MedlinePlus

Efficiency at maximum power ηmx as a function of the exciton Coulomb energy U.
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f3: Efficiency at maximum power ηmx as a function of the exciton Coulomb energy U.

Mentions: To further demonstrate the power of this method, we next discuss the effect of Coulomb interactions on the efficiency. In the Hamiltonian of Eq. (1), the A-LUMO energy, , already includes the Coulomb repulsion energy on the acceptor4. In excitonic systems, the Coulomb interaction is typically considered through the “exciton binding energy”, defined by the Coulomb interaction term between an electron at the D-LUMO and a hole in the D-HOMO. While in methods such as non-equilibrium Green's function adding Coulomb interaction requires substantial effort, the present method does not require either additional technical complexity or additional computational power to account for any Coulomb interaction effects. In Fig. 3 we show the efficiency at maximum power ηmx as a function of the exciton Coulomb energy U (which can be estimated from, e.g. density-functional calculations). We set λepht = 0.1 eV and λephn = 0.2 eV. We find an almost linear decrease in the efficiency, with a reduction of ~15% for U = 0.2 eV.


The molecular photo-cell: quantum transport and energy conversion at strong non-equilibrium.

Ajisaka S, Žunkovič B, Dubi Y - Sci Rep (2015)

Efficiency at maximum power ηmx as a function of the exciton Coulomb energy U.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321170&req=5

f3: Efficiency at maximum power ηmx as a function of the exciton Coulomb energy U.
Mentions: To further demonstrate the power of this method, we next discuss the effect of Coulomb interactions on the efficiency. In the Hamiltonian of Eq. (1), the A-LUMO energy, , already includes the Coulomb repulsion energy on the acceptor4. In excitonic systems, the Coulomb interaction is typically considered through the “exciton binding energy”, defined by the Coulomb interaction term between an electron at the D-LUMO and a hole in the D-HOMO. While in methods such as non-equilibrium Green's function adding Coulomb interaction requires substantial effort, the present method does not require either additional technical complexity or additional computational power to account for any Coulomb interaction effects. In Fig. 3 we show the efficiency at maximum power ηmx as a function of the exciton Coulomb energy U (which can be estimated from, e.g. density-functional calculations). We set λepht = 0.1 eV and λephn = 0.2 eV. We find an almost linear decrease in the efficiency, with a reduction of ~15% for U = 0.2 eV.

Bottom Line: The molecular photo-cell is a single molecular donor-acceptor complex attached to electrodes and subject to external illumination.Moreover, this system includes electrons, phonons and photons, and environments which induce coherent and incoherent processes, making it a challenging system to address theoretically.Here, using an open quantum systems approach, we analyze the non-equilibrium transport properties and energy conversion performance of a molecular photo-cell, including both coherent and incoherent processes and treating electrons, photons, and phonons on an equal footing.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.

ABSTRACT
The molecular photo-cell is a single molecular donor-acceptor complex attached to electrodes and subject to external illumination. Besides the obvious relevance to molecular photo-voltaics, the molecular photo-cell is of interest being a paradigmatic example for a system that inherently operates in out-of-equilibrium conditions and typically far from the linear response regime. Moreover, this system includes electrons, phonons and photons, and environments which induce coherent and incoherent processes, making it a challenging system to address theoretically. Here, using an open quantum systems approach, we analyze the non-equilibrium transport properties and energy conversion performance of a molecular photo-cell, including both coherent and incoherent processes and treating electrons, photons, and phonons on an equal footing. We find that both the non-equilibrium conditions and decoherence play a crucial role in determining the performance of the photovoltaic conversion and the optimal energy configuration of the molecular system.

No MeSH data available.


Related in: MedlinePlus