Efficiency Enhancement of GaAs Photovoltaics Due to Sol-Gel Derived Anti-Reflective AZO Films

Aluminum (Al)-doped ZnO (AZO) thin films are prepared via the sol-gel method and utilized as an anti-reflective coating (ARC) to enhance the light gathering capability and short-circuit current density (Jsc) of GaAs solar cells. The AZO films are prepared chemically by spin coating the sol with an aqueous solution of zinc acetate dihydrate and aluminum nitrate. The current-voltage measurements of the solar cells confirm that the AZO film increases short-circuit current. 4 atom% Al-doped ZnO film exhibits the best anti-reflective characteristics. The conversion efficiency of cells is significantly enhanced by the ARC (8.3% versus 11.2%). The AZO film, which has a suitable refractive index and excellent transmittance, reduces reflectance and significantly enhances the external quantum efficiency of GaAs solar cells compared to those obtained for an undoped ZnO coating. In degradation tests of the solar cells after irradiation treatment, the ZnO and AZO coatings both exhibit lowered J-V characteristics and external quantum efficiency decay of the solar cell after proton irradiation, making them suitable for use as the radiation-resistant and anti-reflective layer in GaAs solar cells.