Charge enhancement of organic materials that was deduced more than two decades ago by means of capacitance-voltage (C-V) measurements meets with difficulties and controversial explanations when using the classical semiconductor theory. Experimentally, it has been found that the charge localization results in nonstationary and frequency-dependent behavior in the-C-V measurements. Detailed analyses of the experimental results provide insight on how to interpret the quantities for concentration and relaxation time of charges in organic semiconductors. The experimental results indicate that the charge localization and conduction occur mainly in the bulk of the poly(3, 3"'-didodecyl-quaterthiophene) (PQT) semiconducting polymer. (c) 2006 American Vacuum Society.