Fabrication and post-chemical-etched surface texturing of H and Ti co-doped ZnO film for silicon thin-film solar cells

In this study, H and Ti co-doped ZnO thin-films were prepared by radio frequency magnetron sputtering with a target containing 1 wt% TiO2 on glass substrates at room temperature. The structural, electrical, and optical properties of HTZO films were investigated with respect to the variation in film thickness. The results indicated that all the HTZO films had a hexagonal wurtzite structure and showed a good c-axis orientation perpendicular to the substrate. The crystallinity and grain size increased as the film thickness increased. The resistivity decreased from 12.58x10(-4) to 5.75x10(-4) Omega.cm. In order to enable the application of HTZO films in Si thin-film solar cells, the optimal HTZO films were post-chemical etched in diluted HCl and NaOH, respectively, at various times. The HCl-etched specimens showed crater-like features and the NaOH-etched film showed hole characteristics. With increasing etching time, the root mean square roughness first increased and then decreased, while the sheet resistance increased with etching time. A HTZO film with high light trapping abilities is achieved with a total transmittance of nearly 90%, and haze values of 78.7%, 47.74%, and 26.35% at 550 nm, 800 nm, and 1100 nm, respectively, by etching with HCl for 30 s. It is found that the chemical wet etched HTZO glass substrate is useful for enhancing the short circuit current for Si thin-film solar cells.