Serial cosputtering for aluminum doping manipulated zinc oxide as front contact for Cu(In,Ga)Se2 solar cells

Aluminum zinc oxide (AZO) thin films were deposited by modified in-line direct current magnetron sputtering - so-called serial cosputtering - using two commercial rotatable targets. A metallic aluminum target (secondary target) was used to condition the surface of a rotatable ceramic aluminum-doped zinc oxide target (ZnO:Al2O3 wt %) as the primary target from which the film was deposited. Consequently, the direct current power applied to the secondary target enabled the variation of doping concentration in the deposited film. An optical transmittance >80% with an improved resistivity (