Electrical impedance studies of optimized standard P3HT:PC 70 BM organic bulk heterojunctions solar cells Walid Aloui ⇑ , Adnen Ltaief, Abdelaziz Bouazizi Laboratory of Physics of Condensed Matter and Nanosciences, Faculty of Sciences of Monastir, Avenue of the Environment, 5019 Monastir, Tunisia article info Article history: Received 26 April 2014 Received in revised form 27 July 2014 Accepted 29 July 2014 Available online 20 August 2014 Keywords: Interfaces Thin films Fullerenes Dielectric properties Transport properties abstract Charge carrier diffusion and recombination in an absorber blend of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C 70 -butyric acid methyl ester (PCBM) with indium tin oxide (ITO) and aluminum contacts have been analyzed by means of impedance spectroscopy. The capacitance exhibits Mott–Schottky behavior indicating the formation of a Schottky junction (band bending) at the P3HT:PCBM/Al interface. Built-in potential of 0.88 V and acceptor impurities concentrations of 9.3  10 15 cm 3 was calculated through capacitance measurements. Impedance measurement shows, at high frequency, an inclined straight line indicates the inhomogeneous nature of the electrode–organic interface. On the other hand, the arc localized at low-frequency is attributed to recombination in the photoactive blend. Global mobility is in the range of 1.1–1.4  10 3 cm 2 V 1 s 1 , which is slightly higher as compared to the literature. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Organic conducting materials are the heart of bulk heterojunctions (BHJ) solar cells, a promising alternative to silicon-based solar cells due to their optical, electronic and mechanical properties [1]. http://dx.doi.org/10.1016/j.spmi.2014.07.051 0749-6036/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +216 55956352. E-mail address: alouiwalid26@yahoo.fr (W. Aloui). Superlattices and Microstructures 75 (2014) 416–423 Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices