| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 77691 | Solar Energy Materials and Solar Cells | 2016 | 7 Pages |
•A roughness-enhanced metal back reflector (BR) for a thin film solar cell was fabricated by depositing silver (Ag) on aluminum (Al) film.•Surface roughness of the Ag–Al film is significantly influenced by the incorporation of Al into Ag.•Morphology and optical properties of the Ag–Al film depend on the Ag deposition temperature.•Hydrogenated amorphous silicon (a-Si:H) thin film solar cells were fabricated on rough surface Ag–Al BRs.
An effective light trapping method for substrate-type hydrogenated amorphous silicon (a-Si:H) thin film solar cells is the use of a back reflector (BR) of high roughness, e.g., ‘hot silver’, which is deposited at temperatures higher than 450 °C. In this work, textured silver-aluminum (Ag–Al) BR films were fabricated by depositing Ag on Al film at Ag-deposition temperatures (TAg) ranging from 25 to 350 °C. The surface morphology and roughness of Ag–Al films were strongly affected by TAg. The Al and Ag films were formed entirely of Ag2Al alloy at TAg of 330 °C or higher, while the Ag–Al films maintained a double-layered structure at 290 °C or below. Although the films did not undergo alloying at TAg of 290 °C, the Ag–Al films have a well-developed surface structure with high diffuse-reflectance, compared to Ag films deposited at the same temperature. The conversion efficiency of an a-Si:H thin film solar cell on a flexible stainless steel substrate increased from 7.63% to 8.44% as TAg was increased from 25 to 290 °C, as a result of more effective light scattering by Ag–Al BRs, producing increased short-circuit current. However, at higher TAg, Ag2Al alloy films with sharp crystallite edges were formed, and were not appropriate as BRs. The present work clearly shows that double-layered Ag–Al films fabricated at temperatures as low as 290 °C could be useful back reflectors for substrate-type thin film solar cells.
