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Dynamics of photoconductivity in organic TPD films

K. SHIMAKAWA1,* , NAZRUL ANUAR1, K. YONEZAWA1, T. SATO1

Affiliation

  1. Department of Electrical and Electronic Engineering, Gifu University, Gifu 501-1193, Japan

Abstract

The steady state photoconductivity in disordered tri-methylphenyl diamine (TPD) films has been studied at relatively high temperatures (200 – 300 K). Hopping transport of holes occurs through localized centers with a Gaussian energy distribution. The steady state photoconductivity is proportional to Gexp[-(/(kT)2/2] (with   0.5) where G is the number of absorbed photons and  (= 0.067 eV) is the standard deviation of the Gaussian distribution. We have formulated the hopping photoconductivity and reasonable physical parameters, such as the hopping relaxation time, recombination time, and diffusion coefficient (and hence mobility) of the charge carriers, are estimated for the TPD films. The photoconductivity increases upon exposure to air and this is a reversible effect..

Keywords

Organic TPD films, Photoconductivity, Hopping of photocarriers, Bimolecular recombination, Exposing air.

Submitted at: Nov. 28, 2006
Accepted at: Jan. 15, 2007

Citation

K. SHIMAKAWA, NAZRUL ANUAR, K. YONEZAWA, T. SATO, Dynamics of photoconductivity in organic TPD films, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 1, pp. 65-69 (2007)