Bandgap calculation of a 2-D photonic crystal and its application towards a thin film solar cell

Abstract

Two-dimensional (2-D) photonic crystals (PhCs) of a square lattice have been investigated to find the complete photonic band gap. Band diagram calculations have been performed using the simulator PWE band solver of the software package optiFDTD™, based on a plane wave expansion method. Air holes in the dielectric background with four different shapes have been considered. Parameters like filling fraction, rod/air hole orientation angle and material dielectric constant have been varied. It has been found that PhCs with square air holes have the largest gap; the gap-midgap ratio is 13.66% for GaAs (when filling fraction, f=0.680 and orientation angle, θ=30°). Finally, a proposal is made to improve the efficiency of a thin film solar cell using this photonic crystal as a back reflector. © 2011 Photonics Society of Poland.