Design of light trapping structures for light-absorption enhancement in thin film solar cells

Light trapping structures with top subwavelength dielectric gratings and back metallic triangle substrate attached to amorphous Si (a-Si) thin film solar cells (TFSCs) are studied. As a result of the grating diffraction effect and surface-plasmon polaritons on substrate, obvious optical absorption enhancement can be achieved in broad wavelength range especially for transverse magnetic (TM) polarized light. Rigorous coupled-wave analysis (RCWA) numerical calculation shows that, compared with bare a-Si TFSCs, the average enhancement is above 20% in the presupposed wavelength range from 0.3 to 1.1 μm as the incident angle varies from 0° to 60°, and 30% more absorption would be increased when the incident light is TM only.