Studies on InZnMgO amorphous buffer layer for Cu(In,Ga)(S,Se)2 solar cell

Abstract

This study explores the effectiveness of an amorphous buffer layer, specifically Indium Zinc Magnesium Oxide (IZMO), as an alternative buffer in Copper Indium Gallium Sulfide Selenide (CIGSSe) solar cells. The findings reveal a significant impact on efficiency through precise adjustment of the Mg/(In+Zn+Mg) ratio (MIZM) from 0 to 0.23. The bandgap exhibits a consistent increase with an ascending Mg/(In+Zn+Mg) ratio, transitioning from 3.42 eV to 3.63 eV for IZMO prepared with Ar and from 3.18 eV to 3.53 eV for IZMO prepared with an Ar+O₂ gas mixture, respectively. This rise is attributed to the augmentation of the conduction band minimum (E_C) of IZMO resulting from the addition of MgO. Moreover, an increase in the Mg/(In+Zn+Mg) ratio correlates with improved conversion efficiency, escalating from 6.31 % to 9.19 %. Notably, the open-circuit voltage experiences a rise from 0.430 V to 0.520 V. This is attributed to the heightened E_C of IZMO due to MgO addition, which mitigates recombination between the light-absorbing layer and the buffer layer, consequently elevating the open circuit voltage. The addition of MgO also enhances the resistance of the buffer layer, contributing to an increase in shunt resistance and a subsequent decrease in leakage current. Conversely, IZMO introduced with O₂ exhibits inferior performance akin to IZO, attributable to substantial sputter damage induced by O₂ introduction.