Investigation of photon-induced transient conductive and dielectric properties of MEH-PPV thin films

POLY 527

Weilou Cao, wlcao@lps.umd.edu1, Min Du, mindu@eng.umd.edu1, Yi-Hsing Peng1, Warren N. Herman, herman@lps.umd.edu2, and Chi. H. Lee, chlee@lps.umd.edu1. (1) ECE, University of Maryland, College Park, MD 20742, (2) Laboratory for Physical Sciences, University of Maryland, College Park, 8050 Greenmead Dr, College Park, MD 20740
We report, for the first time, the direct measurement of photoconductivity using two equal intensity 400 nm laser beams with variable time delay to illuminate one MEH-PPV interdigitated switch to study dynamic photoconductive properties. We also report the measurement of photo-induced change in reflectivity in MEH-PPV using a two-color femtosecond laser system. Photo-induced carrier densities at various pump levels were determined and a carrier generation quantum efficiency of greater than 0.5% was obtained. A peak transient mobility up to 800 cm2/Vs was estimated. Measurements of both photoconductivity and reflectivity change verified that the lifetime of the photo-induced carriers in MEH-PPV is less than 1ps.