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Water-induced polaron formation at the pentacene surface: Quantum mechanical molecular mechanics simulations (Articolo in rivista)

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Water-induced polaron formation at the pentacene surface: Quantum mechanical molecular mechanics simulations (Articolo in rivista) (literal)

Anno

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Alternative label

Cramer, Tobias (1); Steinbrecher, Thomas (2),(3); Koslowski, Thorsten (4); Case, David A. (2),(3); Biscarini, Fabio (5); Zerbetto, Francesco (1) (2009)
Water-induced polaron formation at the pentacene surface: Quantum mechanical molecular mechanics simulations
in Physical review. B, Condensed matter and materials physics; American Institute of Physics, Woodbury [NY] (Stati Uniti d'America)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

Cramer, Tobias (1); Steinbrecher, Thomas (2),(3); Koslowski, Thorsten (4); Case, David A. (2),(3); Biscarini, Fabio (5); Zerbetto, Francesco (1) (literal)

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Note

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(1) Univ Bologna, Dipartimento Chim G Ciamician, I-40126 Bologna, Italy (2) Rutgers State Univ, BioMaPS Inst, Piscataway, NJ 08854 USA (3) Rutgers State Univ, Dept Chem & Chem Biol, Piscataway, NJ 08854 USA (4) Univ Freiburg, Inst Phys Chem, D-79104 Freiburg, Germany (5) CNR, Inst Study Nanostruct Mat, I-40129 Bologna, Italy (literal)

Titolo

Water-induced polaron formation at the pentacene surface: Quantum mechanical molecular mechanics simulations (literal)

Abstract

Water is an omnipresent polar impurity that is expected to be the origin of many electric degradation phenomena observed in organic semiconductors. Here, we describe a microscopic model for polaron formation in the outermost layer of a pentacene crystal due to the polarization of a nearby water layer. The efficient coupling of a classical force field that describes the liquid with a tight-binding model that represents the pi system of the organic layer permits the calculation of nanosecond length trajectories. The model predicts that the reorientation of water dipoles stabilizes positive charge carriers on average by 0.6 eV and thus leads to a polaron trap state at the liquid interface. Thermal fluctuations of the water molecules provoke two-dimensional diffusive hopping of the charge carrier parallel to the interface with mobilities of up to 0.6 cm(2) s(-1) V(-1) and lead to an amorphous broadening of the valence-band tail. As a consequence, water-filled nanocavities act as trapping sites in pentacene transistors. Instead, a complete wetting of the organic film is expected to result in fast thermally activated hopping transport. Polaron trapping is thus not expected to be a limiting factor for transistor-based sensors that operate under water. (literal)

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