Blazed pyramidal gratings for enhanced light trapping in very thin film solar cells

The periodic dielectric blazed grating structure has been employed in this paper to enhance light absorption in amorphous silicon thin film solar cells (TFSC). An AZO pyramidal grating at the back of a very thin film of a-Si:H (165 nm). The blazed grating structure is able to scatter the incident light at angles greater than the critical angle, resulting in total internal reflection at the top surface. Light is trapped within the solar cell due to repeated total internal reflection. Full wave simulations show that the designed grating structure can enhance light absorption in the semiconductor layer from 600 nm to 700 nm. We are able to achieve a short circuit current (Jsc) of 15.34 mA/cm² with an equivalent Si thickness of 165 nm. The calculated Jsc is enhanced by 38.7% at normal incidence while the surface area is increased by only 7.62% relative to a planar TFSC of a-Si thickness 165 nm. Preliminary fabrication of AZO films with a thickness gradient is achieved using the glancing angle deposition method.