RF magnetron sputtering processed transparent conductive aluminum doped ZnO thin films with excellent optical and electrical properties

Aluminum doped ZnO thin films (AZO), which simultaneously transmit light and conduct electrical current, are widely applied in photovoltaic devices. To achieve high performance AZO thin films, the effects of RF magnetron sputtering conditions on the optical and electrical properties of the films have been explored. The optimized AZO thin films exhibit strong (002) orientated growth with hexagonal wurtzite structure. The minimum resistivity of 0.9 × 10⁻³ Ω cm, the highest carrier concentration of 2.8 × 10²⁰ cm⁻³, the best Hall mobility of 22.8 cm² (V s)⁻¹ and average transmittance above 85% can be achieved at the optimum deposition condition of 0.2 Pa, 120 W and 200 °C. Considering the single parabolic band model, the bandgap shift by carrier concentration of the films can be attributed to the Burstein-Moss effect. The results indicate that RF magnetron sputtered AZO thin films are promising for solar cell applications relying on front contact layers.