Enhancement of light absorption in thin film solar cells with metallic nano-strips

Numerical analysis using both Finite Element and Rigorous Coupled Wave Methods are used to examine the impact of salient parameters on the absorption and enhanced field distribution in a thin film solar cell with metallic nano-strip structures. The absorption enhancement in these structures is due to light coupling into both plasmonic and guided wave modes. It is shown that the combination of these modes could overcome the drawbacks of angle, wavelength and polarization selectivity. The simulation results show also that the metallic strips are much more efficient when on the bottom rather than on the top of the active layer (Si), that the thickness of an the optimum passivation SiO₂ layer thickness varies with the wavelength of the incident light, suggesting that a SiO₂ layer with non-uniform thickness might be better for optimum overall absorption and efficiency. From the calculated field distribution as a function of both the strips depth and width, it appears that the field strength in the active layer is much more affected by the changes in the width rather than in the depth.