Tailoring of optoelectronic and trapping effects in ZnO and ZnO:Mg 1D structures for DSSC photoelectrodes

Abstract

This work is focused on tailoring optoelectronic behavior and trapping effects in ZnO and ZnO:Mg 1D nanostructures intended for DSSC photoelectrodes. ZnO and ZnO:Mg deposits on FTO-glass substrates were obtained by the CBD method at a relatively low temperature (90 °C) and short processing time (2 h). In addition, magnesium was incorporated as a dopant and varied (1 and 2 at. %) to obtain ZnO:Mg deposits with different optoelectronic and morphological characteristics. SEM results revealed the morphological evolution of ZnO deposits, transitioning from nanotubes to nanorods as the Mg increases from 0 to 2 at. %. Raman and XPS spectroscopies confirmed the formation of ZnO Wurtzite structures, as well as the incorporation of Mg ions in the ZnO host lattice. On the other hand, UV–Vis DRS revealed a significant influence of Mg ion concentration on the reflectance and optical bandgap of ZnO deposits. PL results indicated that both ZnO and ZnO:Mg deposits are rich in defects and traps induced by Mg incorporation, enabling the tailoring of optoelectronic properties. Additionally, when Mg at. % increases, UV, blue, and infrared emissions are quenched, while yellow emissions are enhanced. Lastly, a comprehensive analysis of the characteristics and behavior of resulting materials indicates that ZnO:Mg with 1 at. % of Mg exhibits the best attributes for photoelectrode, such as increased surface area, enhanced crystalline quality, and reduced recombination rates and defects. Noteworthy is that resulting materials exhibit those crucial characteristics required for DSSC photoelectrodes applications, and they could be considered for flexible electronic applications.