Characterization of Cd-Free Zn1–xMgxO:Al/Zn1–xMgxO/Cu(In,Ga)(S,Se)2 Solar Cells Fabricated by an All Dry Process Using Ultraviolet Light Excited Time-Resolved Photoluminescence

Cd-free Cu(In,Ga)(S,Se) 2 (CIGSSe) solar cells with a structure of glass/Mo/CIGSSe/Zn 1– x Mg x O (buffer)/Zn 1– x Mg x O:Al (TCO), fabricated by an all dry process, are characterized using ultraviolet light excited time-resolved photoluminescence (UV-TRPL). The impact of bandgap energy ( E g ) values of buffer and transparent conductive oxide (TCO) layers, denoted by E g of buffer and TCO, is examined. The E g values of buffer and TCO layers are kept almost similar and varied from 3.30 to 3.94 eV. In this work, UV-TRPL measurement is performed to examine the UV-TRPL carrier lifetimes near the Zn 1– x Mg x O buffer/CIGSSe interface in the solar cell structure. It is revealed that the UV-TRPL carrier lifetimes near the Zn 1– x Mg x O buffer/CIGSSe interface in Cd-free solar cells are increased upon enhancing the E g of buffer and TCO from 3.30 to 3.94 eV, thus increasing the open-circuit voltage and fill factor. Additionally, short-circuit current density is enhanced up to about 38 mA/cm 2 owing to the highly transparent Zn 1– x Mg x O/Zn 1– x Mg x O:Al layers. Ultimately, an 18.5%-efficient Cd-free solar cell with the E g of buffer and TCO of 3.94 eV, prepared by an all dry process, is fabricated, which has the same level of 18.3% for the reference solar cell (glass/Mo/CIGSSe/CdS/ZnO/ZnO:Al).