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Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz spectroscopy

H. Nemec ; H. K. Nienhuys ; Erik Perzon (Institutionen för kemi- och bioteknik, Polymerteknologi) ; F. L. Zhang ; O. Inganas ; P. Kuzel ; V. Sundstrom
Physical Review B (1098-0121). Vol. 79 (2009), 24, p. 245326 (art no).
[Artikel, refereegranskad vetenskaplig]

Time-resolved terahertz spectroscopy and Monte Carlo simulations of charge-carrier motion are used to investigate photoinduced transient conductivity in a blend of a low-band-gap polyphenylene copolymer and fullerene derivative. The optical excitation pulse generates free holes delocalized on polymer chains. We show that these holes exhibit a very high initial mobility as their initial excess energy facilitates their transport over defects (potential barriers) on polymer chains. The conductivity then drops down rapidly within 1 ps, and we demonstrate that this decrease occurs essentially by two mechanisms. First, the carriers loose their excess energy and they thus become progressively localized between the on-chain potential barriers-this results in a mobility decay with a rate of (180 fs)(-1). Second, carriers are trapped at defects (potential wells) with a capture rate of (860 fs)(-1). At longer time scales, populations of mobile and trapped holes reach a quasiequilibrium state and further conductivity decrease becomes very slow.

Nyckelord: energy gap, fullerenes, hole mobility, Monte Carlo methods, photoconductivity, polymer blends, terahertz wave spectra, time, resolved spectra, charge-carrier mobility, conjugated polymers, bulk heterojunction, dynamics, time, photogeneration, polythiophene, transport, disorder, chains



Denna post skapades 2010-03-01. Senast ändrad 2013-05-22.
CPL Pubid: 116728

 

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Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Polymerteknologi (2005-2014)

Ämnesområden

Den kondenserade materiens fysik

Chalmers infrastruktur