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.</p>.
|Journal||Physical Review B (Condensed Matter and Materials Physics)|
|Publication status||Published - 2009|
Bibliographical noteThe information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Chemical Physics (S) (011001060)
Subject classification (UKÄ)
- Atom and Molecular Physics and Optics
- polymer blends
- Monte Carlo methods
- hole mobility
- energy gap
- terahertz wave spectra
- resolved spectra