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

作者：Nemec Hynek^*; Nienhuys Han Kwang; Perzon Erik; Zhang Fengling; Inganas Olle; Kuzel Petr; Sundstrom Villy

来源：Physical Review B, 2009, 79(24): 245326.

DOI：10.1103/PhysRevB.79.245326

• energy gap
• fullerenes
• hole mobility
• Monte Carlo methods
• photoconductivity
• polymer blends
• terahertz wave spectra
• time resolved spectra

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..

• 出版日期2009-6