Characterization of transport properties of organic semiconductors using impedance spectroscopy

Abstract

Methods for the determination of drift mobility, localized-state distribution and deep trapping lifetime in organic semiconductors using impedance spectroscopy are reviewed. The theoretical basis is single-injection space-charge-limited current under small sinusoidal voltage perturbation. Major advantages of impedance spectroscopy are: full automatic measurements and simultaneous measurements of these physical quantities. Information on these physical quantities are essential for the understanding of transport properties in organic semiconductors and for the design of organic devices such as organic light-emitting diodes and organic solar cells using a device simulator. The determination of drift mobility, localized-state distribution and deep trapping lifetime from impedance spectra is demonstrated in a molecularly doped polymer. A molecularly doped polymer is a prototypical organic semiconductor and is a good example for the demonstration of simultaneous determination of these quantities. The methods presented here are applicable to insulating semiconductors and thus to inorganic disordered semiconductors such as hydrogenated amorphous silicon and amorphous oxide semiconductors, as well.