Copper-induced crystallization of sputtered silicon on ZnO:Al substrate and the textured interface for light trapping

Copper-induced crystallization of a-Si on ZnO:Al (AZO) substrate is studied. On Ar sputtered AZO substrate, the optimized crystallite and crystalline ratio of poly-Si are ∼30 nm and ∼71%, respectively. O2 is also introduced and optimized when preparing AZO substrates. On AZO substrate with O2/Ar + O2 = 3%, the crystallite and crystalline ratio of poly-Si are greatly improved, showing ∼40 nm and ∼82%, respectively. Textured AZO is prepared for analyzing the light-trapping efficiency. With 40 s etching in 0.5% HCl, ∼0.7 μm lateral scale and ∼119 nm root mean square roughness is obtained. The scattering property is verified by the flat step over a large angle range in the angular distribution measurement. 660 nm Cu-induced poly-Si on this AZO substrate shows an average reflectivity of ∼17.7%, only 45% of the flat Si, showing a good light-trapping efficiency and a potential use in solar cells.