Mobility and density relaxation of photogenerated charge carriers in organic materials

We have measured mobility and density relaxation of photogenerated charge carriers in regiorandom poly(3-hexylthiophene) using novel extraction current transient techniques. We show how to obtain time-dependent mobility mu and charge carrier density p using independent measurements. The results show mu proportional to iota(-0.42) independent on charge carrier density. The carrier density follows a bimolecular decay with the bimolecular recombination coefficient beta = 7.2 x 10(-13) cm(3)/s. The measured time-of-flight current follows closely the estimated time decay as j(t) proportional to p(t)mu(t), with deviation arising from extraction of the generated charge carriers. (C) 2004 Elsevier B.V. All rights reserved.