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Although various optical designs and physical mechanisms have been studied both experimentally
and theoretically to improve the optical absorption of organic solar cells (OSCs) by incorporating
metallic nanostructures, the effects of plasmonic nanostructures on the electrical properties of OSCs
is still not fully understood. Hence, it is highly desirable to study the changes of electrical properties
induced by plasmonic structures and the corresponding physics for OSCs. In this work, we develop a
multiphysics model for plasmonic OSCs by solving the Maxwell’s equations and semiconductor
equations (Poisson, continuity, and drift-diffusion equations) with unified finite-difference method.
Both the optical and electrical properties of OSCs incorporating a 2D metallic grating anode are
investigated. For typical active polymer materials, low hole mobility, which is about one magnitude
smaller than electron mobility, dominates the electrical property of OSCs. Since surface plasmon
resonances excited by the metallic grating will produce concentrated near-field penetrated into the
active polymer layer and decayed exponentially away from the metal-polymer interface, a
significantly nonuniform and extremely high exciton generation rate is obtained near the grating.
Interestingly, the reduced recombination loss and the increased open-circuit voltage can be achieved
in plasmonic OSCs. The physical origin of the phenomena lies at direct hole collections to the
metallic grating anode with a short transport path. In comparison with the plasmonic OSC, the hole
transport in a multilayer planar OSC experiences a long transport path and time because the standard
planar OSC has a high exciton generation rate at the transparent front cathode. The unveiled
multiphysics is particularly helpful for designing high-performance plasmonic OSCs.
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