Multiphysics modeling of plasmonic organic solar cells with a unified finite-difference method

A multiphysics study carries out on plasmonic organic solar cells (OSCs) by solving Maxwell's equations and semiconductor (Poisson, drift-diffusion, and continuity) equations simultaneously with unified finite-difference framework. Regarding the Maxwell's equations, the perfectly matched layer and periodic boundary conditions are imposed at the vertical and lateral directions of OSCs to simulate the infinite air region and metallic grating electrode, respectively. In view of the semiconductor equations, the Scharfetter-Gummel scheme and semi-implicit strategy are adopted respectively in the space and time domains. To model the bulk heterojunction OSCs, the Langevin bimolecular recombination and Onsager-Braun exciton dissociation models are fully taken into account. The exciton generation rate depending on the optical absorption of the organic active material can be obtained by solving the Maxwell's equations and will be inserted into the semiconductor equations. Through the multiphysics model, we observed the increased shortcircuit current and dropped fill factor when OSCs incorporate a metallic grating anode supporting surface plasmon resonances. This work provides fundamental multiphysics modeling and understanding for plasmonic organic photovoltaics.