How using the modified measurement technique of capacitance for three-terminal devices and apply this method for the evaluation of the channel formation in organic thin film transistors.
The attached article is a good start point for you:
Tanaka, Y., Noguchi, Y., Kraus, M., Brütting, W. and Ishii, H., 2013. Three-terminal capacitance–voltage measurements of pentacene field-effect transistors during operation. Organic Electronics, 14(10), pp.2491-2496.