The importance of the methanol content in the precursor solution, on the physical properties of cadmium oxide thin films prepared by the sol–gel method

Undoped and fluorine doped cadmium oxide films were obtained by the sol–gel technique, starting from a simple precursor solution constituted of: cadmium acetate, methanol, glycerol and triethylamine and only for doped samples, ammonium fluoride as the fluoride source. Due to the methanol content used is higher with respect to the other reagents, variations in this parameter affect the viscosity and gelation time of the precursor solution, giving as result changes in the thickness. The importance of the methanol content in the growing solution on the structural, morphological, optical and electrical properties of the films is reported. Higher thickness was obtained for lower methanol content, in the range 33–46 mol, in the growing solution. Largest growing rate was obtained when the methanol content in the precursor solution was 33 mol. The films showed good characteristics for their use as transparent conductive films in solar cells.

Research highlights▶ This work is important due to the recent interest for obtaining CdO films by simple and economical techniques. The sol–gel technique shows these characteristics. However, CdO films with higher thicknesses could be obtained starting from a high number of coats. In this work, the importance of the methanol content in the precursor solution on the physical properties of cadmium oxide thin films prepared by the sol–gel method was studied. For the first time, higher thicknesses of CdO films were obtained with a lower number of coats, changing the methanol content in the precursor solution. The films show good electrical, optical, structural properties for their use as transparent conductive films in solar cells.