Solar Energy Materials & Solar Cells 90 (2006) 900–915 Modeling charge transport in composite solar cells C.M. Martin, V.M. Burlakov, H.E. Assender à Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK Received 27 March 2005; received in revised form 21 April 2005; accepted 2 May 2005 Available online 22 June 2005 Abstract Solar cells based on conjugated polymers are often designed to be nanostructured heterojunctions, with the aim of providing a large interface area for exciton dissociation. While such devices have been shown to be efficient at splitting excitons, the improvements in efficiency have not been as great as would be expected, with losses due to recombination being identified as a major problem. We therefore apply a simple drift-diffusion model to such a system to investigate how changing the interface area affects the short circuit current. We find that for a given system, there is a clear optimum device thickness and that increasing the interface area at the expense of device thickness past this value will lead to a decrease in solar cell efficiency. r 2005 Elsevier B.V. All rights reserved. Keywords: Organic–inorganic composite solar cell; Interface morphology; Charge transport; Short circuit current 1. Introduction Solar cells based on conjugated polymers [1,2] are attractive due to their potential for low-cost manufacture. Power conversion efficiencies are currently approaching the values required for commercial viability, with a considerable amount of research ARTICLE IN PRESS www.elsevier.com/locate/solmat 0927-0248/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.solmat.2005.05.009 à Corresponding author. Tel.: +44 1865 273781; fax: +44 1865 273789. E-mail address: hazel.assender@materials.ox.ac.uk (H.E. Assender).