A computational framework to investigate charge transport in heterogeneous organic photovoltaic devices

Low cost per watt and mechanical flexibility of organic solar cells (OSCs) make it a promising alternative to traditional inorganic solar cells. Recently, conjugated polymer based organic solar cells with efficiency of 8.13% [1] have been reported. Experimental results suggest that the distribution of the donor and acceptor constituents in the morphology is a key factor in determining the efficiency of such devices. A computational framework that can effectively explore that correlation between morphology and performance would greatly accelerate the development of high efficiency organic photovoltaic devices. In this paper, we develop a scalable computational framework to understand the correlation between nanoscale morphology and performance of OSC. We focus on the charge transport mechanism while considering one-stage interfacial charge generation process. Steady state drift diffusion equations are used for modeling these devices. We discuss the numerical challenges associated with a finite element based simulation of OSC with spatial variation in material properties and large charge density gradients. The effect of microstructure on the distribution of charge densities and electrostatic potential is investigated. The prominent effect of feature size and interface area on the current voltage characteristics is illustrated using realistic microstructures. We showcase the framework by interrogating fully 3D heterogeneous microstructures. (C) 2012 Elsevier B.V. All rights reserved.