Angular Selective Light Filter Based on Photonic Crystals for Photovoltaic Applications

In this paper, we present a new angular selective filter design that is based on photonic bandgap engineering principles. The operation of the filter is based on the occurrence of angular-dependent photonic stopbands and passbands in a photonic crystal structure. Such a filter allows for the propagation of normally incident light while disallowing the propagation of obliquely incident light waves. When the filter is applied to a solar cell structure that consists of a diffraction grating structure on the back surface, a high-efficiency light trap can be formed. Hence, the light-trapping capacity of the new structure is dependent on the photonic band structure of the light filter rather than on refractive optical properties of the active photovoltaic material. This paper presents a model of such a structure and investigates the possibilities afforded by the new structure.