Al-doped zinc stannate films for photovoltaic applications

Al-doped zinc stannate (Zn 2 SnO 4 : Al or Zn-Sn-O: Al or AZTO) has attracted considerable attention as a next-generation transparent conducting oxide (TCO) owing to its properties. In this study, AZTO films were deposited by co-sputtering Al-doped zinc oxide (AZO) and SnO 2 targets at room temperature. The as-deposited AZTO films were confirmed to be satisfactorily adherent with good uniformity. These films had an average transmittance of over 80%, energy band gap of >3.5 eV, and relatively low electrical resistivity of 1.29×10 1 Ω. cm. The composition ratio of Zn/Sn at 140 W of SnO 2 power was approximately 2, indicating the formation of AZTO film with stoichiometric composition of Zn 2 SnO 4 : Al at this power. Further, the Cu(InGa)Se 2 (CIGS) device fabricated with AZTO (140 W) as a TCO exhibited an efficiency of 0.73%, with a V OC of 0.51 V, J} SC of 3.76 mA/cm 2 , and FF of 38.4%. Furthermore, the conversion efficiency of CIGS cell was enhanced to 2.82% by employing the AZTO film deposited at the elevated temperature of 350oC.