The high efficiency of charge generation within organic photovoltaic blends apparently contrasts with the strong “classical” attraction between newly formed electron−hole pairs. Several factors have been identified as possible facilitators of charge dissociation, such as quantum mechanical coherence and delocalization, structural and energetic disorder, built-in electric fields, and nanoscale intermixing of the donor and acceptor components of the blends. Our mesoscale quantum-chemical model allows an unbiased assessment of their relative importance, through excited-state calculations on systems containing thousands of donor and acceptor sites. The results on several model heterojunctions confirm that the classical model severely overestimates the binding energy of the electron−hole pairs, produced by vertical excitation from the electronic ground state. Using physically sensible parameters for the individual materials, we find that the quantum mechanical energy difference between the lowest interfacial charge transfer states and the fully separated electron and hole is of the order of the thermal energy.

Origin of Charge Separation at Organic Photovoltaic Heterojunctions: A Mesoscale Quantum Mechanical View / Casalegno, Mosè; Pastore, Raffaele; Idé, Julien; Po, Riccardo; Raos, Guido. - In: JOURNAL OF PHYSICAL CHEMISTRY. C. - ISSN 1932-7447. - 121:31(2017), pp. 16693-16701. [10.1021/acs.jpcc.7b03640]

Origin of Charge Separation at Organic Photovoltaic Heterojunctions: A Mesoscale Quantum Mechanical View

Pastore, Raffaele;
2017

Abstract

The high efficiency of charge generation within organic photovoltaic blends apparently contrasts with the strong “classical” attraction between newly formed electron−hole pairs. Several factors have been identified as possible facilitators of charge dissociation, such as quantum mechanical coherence and delocalization, structural and energetic disorder, built-in electric fields, and nanoscale intermixing of the donor and acceptor components of the blends. Our mesoscale quantum-chemical model allows an unbiased assessment of their relative importance, through excited-state calculations on systems containing thousands of donor and acceptor sites. The results on several model heterojunctions confirm that the classical model severely overestimates the binding energy of the electron−hole pairs, produced by vertical excitation from the electronic ground state. Using physically sensible parameters for the individual materials, we find that the quantum mechanical energy difference between the lowest interfacial charge transfer states and the fully separated electron and hole is of the order of the thermal energy.
2017
Origin of Charge Separation at Organic Photovoltaic Heterojunctions: A Mesoscale Quantum Mechanical View / Casalegno, Mosè; Pastore, Raffaele; Idé, Julien; Po, Riccardo; Raos, Guido. - In: JOURNAL OF PHYSICAL CHEMISTRY. C. - ISSN 1932-7447. - 121:31(2017), pp. 16693-16701. [10.1021/acs.jpcc.7b03640]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/718723
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