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

Cd-free Cu(In,Ga)(S,Se) (CIGSSe) solar cells with a structure of glass/Mo/CIGSSe/ZnMg O (buffer)/ZnMg 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) values of buffer and transparent conductive oxide (TCO) layers, denoted by E of buffer and TCO, is examined. The E 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 ZnMg O buffer/CIGSSe interface in the solar cell structure. It is revealed that the UV-TRPL carrier lifetimes near the ZnMg O buffer/CIGSSe interface in Cd-free solar cells are increased upon enhancing the E 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 owing to the highly transparent ZnMg O/ZnMg O:Al layers. Ultimately, an 18.5%-efficient Cd-free solar cell with the E 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).