Diode model of nonuniform irradiation treatment to predict multiscale solar-electrical conversion for the concentrating plasmonic photovoltaic system

Abstract

Optical concentrators and plasmonic nanostructured surfaces are promising methods to increase the solar irradiation density and enhance light absorption. The combined application of these two methods for solar cells faces challenges of multiscale solar-electrical conversions, especially the treatment of nonuniform irradiation. A multiscale multiphysics method is proposed to predict the electrical outputs of a concentrating plasmonic photovoltaic (CPV) system. In the model, a series-connected diode global model for concentrating-plasmonic-electrical conversion combined with a local one-unit diode for fully coupled optical-thermal-electrical conversion is employed to treat nonuniform concentrating irradiation. The one-unit diode model is calibrated by J-V curve fitting with the local fully coupled optical-thermal-electrical model to characterize the wavelength-dependent light absorption and charge carrier behaviors. An explicit formula is proposed to consider the influences of concentrating irradiation and plasmonic nanostructures. The feasibility of the calibrated one-unit diode under concentration ratios is validated with the maximum power compared to an experimental GaAs-based solar cell under concentrated sunlight. The electrical outputs of the plasmonic solar cell under nonuniform irradiation is obtained by the equivalent circuit with series-connected diodes. Each of the diodes yields a photogenerated current in its individual state, whereas the equivalent series-connected circuit has a reformulated homogeneous current. The cross current of the series-connected circuit is mainly determined by the solar cell zone with the lowest concentration ratio. The method with a uniform one-sun irradiation assumption in the entire solar cell surface can overestimate its working current before the declining point and can underestimate the open-circuit voltage. The concentration enhances the photogenerated current but induces auxiliary series resistance. The maximum power is a trade-off of the improved photogenerated current and unfavorable series resistance. This work provides theoretical guidance for large-scale engineering applications of CPV systems with nanostructured solar cells.