Influence of nanocellulose concentration on the tunability of energy bandgap of cadmium telluride thin films

Cadmium telluride (CdTe) doped nanocellulose thin films were successfully deposited on glass/fluorine-doped tin oxide substrates from an aqueous electrolyte bath containing hydrated cadmium sulfate (3CdSO4·8H2O) and tellurium dioxide using electrodeposition technique. Six samples of CdTe thin films were grown with nanocellulose concentrations of (0, 1, 3, 5, 7, and 9) ppm. The results obtained from electronic data of the deposited layers using UV–Vis spectrophotometer agree favourably with the theoretical formulation. The bandgap of the films ranges from 1.32 to 1.67 eV. The lowest bandgap of CdTe (1.32 eV) was achieved at a concentration of 9 ppm. This relatively low energy bandgap is remarkable in recent formation of CdTe. Photoelectrochemical cell measurement shows that the electrical conductivity type of undoped CdTe is n-type while the nanocellulose doped CdTe is p-type in electrical conduction. Hence, it is possible to effectively tune the conductive properties of CdTe by careful addition of nanocellulose concentration.