Combined front diffraction and back blazed gratings to enhance broad band light harvesting in thin film solar cells

Nanostructures with front dielectric and back metallic gratings in crystalline silicon (c-Si) thin film solar cells (TFSCs) are proposed. Different front and back gratings are designed. The diffraction effect of front dielectric gratings and surface plasmon polaritons (SPPs) enhancement induced by back metal gratings in the long wavelength range promote the total optical absorption. The simulation demonstrates that the dielectric and triangle metallic gratings have good performance. We achieve about 50 percent average optical absorption enhancement compared with the normal flat cells in a broad spectrum range from 300 to 1100 nm and 80 percent increase at the transverse magnetic (TM) polarized irradiation.