Comment on “Coherence and Uncertainty in Nanostructured Organic

Comment pubs.acs.org/JPCA

Comment on “Coherence and Uncertainty in Nanostructured Organic Photovoltaics” M. Schott*,† and C. Aslangul‡ †

Institut des Nanosciences de Paris, UMR 7588 CNRS, Université Pierre et Marie Curie, 4 Place Jussieu 75252 Paris cedex 05, France Laboratoire de Physique Théorique de la Matière Condensée, UMR 7600 CNRS, Université Pierre et Marie Curie, 4 Place Jussieu 75252 Paris cedex 05, France

‡

J. Phys. Chem. A 2014. DOI: 10.1021/jp412052z aake et al.1 published a letter entitled “Coherence and Uncertainty in Nanostructured Organic Photovoltaics”. The problem of charge separation in organic photovoltaics is indeed an important question and efficient charge separation is not fully understood yet. The authors propose a model, mentioned in the title and expressed in the following sentences, “During the light absorption process, the existence of the photon is uncertain, implying a momentum uncertainty equal to the momentum of the photon. As a result, its position, as well as the position of the photoexcitation it creates, is uncertain as required by Heisenberg famous equation ... “. Unfortunately, this statement is conceptually wrong. It rests on application of the uncertainty relation between momentum and position of the photon. But it is not possible to construct a function of position that could have the meaning of a photon wave function in the position space,2 and therefore this relation cannot be used here. Moreover, they relate a characteristic size of a matter excitation produced by photon absorption to a positional property of the photon. This is unfounded as well: think of the case of excitation of an atom. It is here appropriate to cite Akhiezer:3 “the localization of a photon in a region smaller than a wavelength has no meaning and the concept of probability density for the localization of the photon does not exist”.

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AUTHOR INFORMATION

Notes

The authors declare no competing financial interest.

REFERENCES

(1) Kaake, L. G.; Moses, D.; Heeger, A. J. Coherence and Uncertainty in Nanostructured Organic Photovoltaics. J. Phys. Chem. Lett. 2013, 4, 2264−2268. (2) Cohen-Tannoudji, C.; Dupont-Roc, J.; Grynberg, G. Photons et atomes. Introduction à l’électrodynamique quantique; Interéditions: Paris, France, 1987; p 32. English translation: Cohen-Tannoudji, C.; Dupont-Roc, J.; Grynberg, G. Photons and Atoms: Introduction to Quantum Electrodynamics; Wiley: New York, 1989. (3) Akhiezer, A. I.; Berestetskii, V. B. Quantum Electrodynamics; Interscience: New York, 1965; p 11.

Received: November 27, 2013 Published: January 31, 2014 © 2014 American Chemical Society

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dx.doi.org/10.1021/jp411645j | J. Phys. Chem. A 2014, 118, 1538−1538