Abstract
We report the fabrication of an array of random Silicon nanocones using a KrF excimer laser. A 370 nm thick amorphous Silicon layer deposited on a glass substrate was used in the process. The fabricated nanocones showed a large and broadband absorption enhancement over the entire visible wavelength range. An enhancement up to 350% is measured at λ = 650 nm. Additionally, the laser irradiation caused the nanocones to crystallize. The effect of changing the laser parameters (i.e. energy density, time, and frequency) on the morphology and the absorption is studied and compared. Wide-angle anti-reflective properties have been observed for the fabricated nanocones with less than 10% reflection for angles up to 60°. The major limitation of amorphous silicon thin film solar cells is the reduced absorption. This problem could be solved if light is trapped efficiently inside the thin film without the need of increasing the film thickness. The random array of nanocones presented in this work showed a substantial increase in absorption over a wide angle, were fabricated at a low cost and are easily scalable. This technique offers a fast approach which could significantly help in overcoming the absorption limitation.
Highlights
Thin film amorphous Silicon (a-Si) solar cells have gained an increased attention due to their low energy and cost requirements compared to their crystalline counterparts[1]
Among various 3D nanostructures, silicon nanocones (NCs) are considered as the most efficient light trapping configuration for solar cells because of their improved refractive index matching with air[25]
Large and broadband absorption enhancement is obtained for nanostructured a-Si compared to the bare a-Si
Summary
Thin film amorphous Silicon (a-Si) solar cells have gained an increased attention due to their low energy and cost requirements compared to their crystalline counterparts[1]. The amorphous material suffers from a low carrier diffusion length, due to the randomness of its crystal structure, which significantly limits its thickness to a few hundred nanometers[3] This small thickness reduces the absorption within the solar cell. We report a lithography-free one step fabrication method of large area a-Si NCs using a KrF excimer laser. In this method, the silicon is not etched to produce the NCs as is customary with conventional methods. The current work provides a detailed systematic study on the effect of changing excimer laser parameters on the morphology and optical properties of a-Si
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