Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz spectroscopy
Journal article, 2009
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.
polythiophene
time
terahertz wave spectra
charge-carrier mobility
dynamics
resolved spectra
photoconductivity
photogeneration
fullerenes
disorder
hole mobility
time
Monte Carlo methods
energy gap
bulk heterojunction
conjugated polymers
transport
polymer blends
chains
Author
H. Nemec
H. K. Nienhuys
Erik Per Perzon
Chalmers, Chemical and Biological Engineering, Polymer Technology
Fengling Zhang
Olle Inganäs
P. Kuzel
V. Sundstrom
Physical Review B - Condensed Matter and Materials Physics
24699950 (ISSN) 24699969 (eISSN)
Vol. 79 24 245326 (art no)-Subject Categories
Condensed Matter Physics
DOI
10.1103/PhysRevB.79.245326