Coarse-grained kinetic modelling of bilayer heterojunction organic solar cells

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• 作者：Mosè ; Casalegno^a ; ^{mose.casalegno@chem.polimi.it} ; Chiara Carbonera^b ; ^{chiara.carbonera@eni.com} ; Silvia Luzzati^c ; ^{silvia.luzzati@ismac.cnr.it} ; Guido Raos^a ; ^{guido.raos@polimi.it}
• 关键词：Organic solar cell ; Kinetic Monte Carlo ; Coarse-graining ; Numerical simulations
• 刊名：Organic Electronics
• 出版年：2012
• 期刊代码：137_15661199
• 类别：et
• 出版时间：May, 2012
• 卷：13
• 期：5
• 页码：750-761
• 文件大小：480 K

摘要

The on-lattice kinetic Monte Carlo (KMC) method provides a powerful tool to simulate the J-V properties of organic solar cells. However, the computational cost associated with charge injection may limits its applicability. In the attempt to overcome this limitation, we describe in this paper a coarse-grained numerical approach to photocurrent generation in bilayer heterojunction solar cells. Starting from the KMC algorithm, a self-consistent numerical procedure is proposed to find the steady-state solutions of the kinetic equations describing particle dynamics in one dimension across the layer thickness. Our model incorporates the generation, transport and recombinations of charge carriers, excitons, and electron/hole pairs, whose introduction is required to correctly describe interfacial phenomena at the coarse-grained level. A continuum model of the electrostatic interactions among charge carriers is proposed and used to compute their hopping rates during the simulation. The model is used to investigate the J-V properties of Cathode/PCBM/P3HT/PEDOT:PSS/ITO bilayer devices, showing that Fermi level pinning at the Cathode/PCBM interface must be invoked to accurately model the experimental behavior. From the fitting to the experimental J-V data, we conclude the short-circuit current density to be mainly associated with a high exciton diffusion length. The analogies and differences between our model and existing KMC and drift-diffusion approaches are also discussed.