Lambertian and photonic light trapping analysis with thickness for GaAs solar cells based on 2D periodic pattern

The study proposes designs using 2D photonic crystal (PhC) structure-based thin film heterojunction gallium arsenide (GaAs) solar cell with a periodic pattern having PhC structure extends from top transparent conducting oxide (TCO) to inside the p-AlGaAs window layer placed just above the active layer of GaAs material in one design and in another PhC structure is etched only in TCO. The work presents the comparative analysis of the proposed structure with Lambertian light trapping limits and the planar cell, taken as reference. The study is also performed for double-layer anti-reflective coating (ARC) structure. The study presents the quantitative analysis of the effect of PhC structure in the performance of the design and how the effect varies with the thickness of absorption layer. It has been found that a considerable increase in efficiency has been achieved, especially for thinner active layers, demonstrating the advantage of a wavelength-scale, PhC-based structures for thin-film solar cells. The results have shown that PhC structure (etched till inside p-AlGaAs)-based solar cell exceeds the efficiency of the double ARC-based structure by more than 18% for 50nm thin active layer cell. The parameters have been optimised and calculated by means of rigorous coupled wave analysis (RCWA).