Optimization of Synthesis of ZnO:Al as n-Type Transparent Conductive Layer for Oxide-Semiconductor-Based Solar Cells

摘要

Aluminum-doped zinc oxide was deposited on silicon and glass substrates by magnetron sputtering methods with various conditions starting from conventional, then to oxygen reactive technique, and finally to cosputtering of aluminum and 2% Al2O3 in ZnO target. The results showed that the optical transmittance of the thin films in the visible range was above 80%. The direct bandgap of the aluminum-doped zinc oxide thin films, depending on the deposition conditions, was estimated to lie in the range between 3.2 eV and 4.2 eV. Good electrical properties with resistivity of about 2.5 x 10(-3) Omega cm were also observed when doping more Al using the cosputtering method. Optimization of the synthesis conditions for aluminum-doped zinc oxide thin films was performed using a newly proposed dimensionless figure of merit based on analysis of the efficiency of solar cells. This study highlights that the optimized deposition condition was to cosputter aluminum during a total additional time of 2 min. The results show that such transparent conductive thin films could be applied in future low-cost heterojunction oxide-based solar cells with CuFeO2 delafossite p-type absorber.