Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz spectroscopy
2009 (English)In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 79, no 24, 245326- p.Article in journal (Refereed) Published
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. .
Place, publisher, year, edition, pages
2009. Vol. 79, no 24, 245326- p.
energy gap; fullerenes; hole mobility; Monte Carlo methods; photoconductivity; polymer blends; terahertz wave spectra; time resolved spectra
IdentifiersURN: urn:nbn:se:liu:diva-20160DOI: 10.1103/PhysRevB.79.245326OAI: oai:DiVA.org:liu-20160DiVA: diva2:233671