We fabricated poly(3-hexylthiophene) (P3HT) rectifiers with the 3-dB frequency higher than 2 MHz and analyzed their frequency characteristics using an impedance spectroscopy as well as current density-voltage (J-V) measurement. The J-V characteristics showed a typical diode behavior with good rectification ratio (similar to 5 x 10(4)). We extracted modeling parameters of the equivalent circuit and analyzed the interface and bulk characteristics of the P3HT diode from the impedance plot. The P3HT/Al interface layer shows highest RC constant. The diode with thin P3HT film exhibits lower RC constant at the P3HT/Al interface compared to thick P3HT films and therefore it shows better frequency response. The diode frequency response is analyzed using the P3HT mobility estimated by fitting the J-V characteristics with the space-charge-limited current (SCLC) formula. This mobility is similar to the mobility measured by the time-of-flight photoconductivity technique. (C) 2009 Elsevier B.V. All rights reserved.