Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Organic semiconductors II

HL 52.7: Talk

Friday, March 27, 2009, 12:00–12:15, POT 51

Trapped-space-charge-limited currents: Evaluating analytical approximations by simulation — •Gernot Paasch¹ and Susanne Scheinert² — ¹IFW Dresden, Germany — ²TU Ilmenau, Germany

The well-known analytical approximations for trapped-space-charge-limited currents are widely used in analyzing organic diodes. However, within these approximations, it is not possible to check the validity of the assumptions made in the derivation of the approximations. Besides the neglect of the diffusion current, this concerns especially the relations of the contact work function and of the layer thickness with the doping of the organic semiconductor, the position of the center of the trap distribution and its maximum value, and in the case of a Gaussian trap distribution the approximation for the density of the trapped charge. We present results of full numerical simulations (drift-diffusion model) for a wide range of parameter variation together with the application of the analytical approximations to fit the simulations. From this comparison one can set limits for the parameter ranges in which the approximations can be applied. This is important since other effects can also lead to similar power laws of the current voltage characteristics. In addition, further analytical approximations will be discussed for different combinations of trap distributions and distributions of hopping transport states.