Photocurrent generation using ZnO/CuO/Ag heterojunction films

Abstract

The preparation of heterojunctions in semiconductor films has generated great interest in the field of photocatalysis due to the unique physicochemical properties and a special electronic band structure formed. Particularly, in this work, we show the heterojunction synthesis of ZnO/CuO/Ag films deposited on glass substrates. These films were prepared by the sol–gel method coupled with the spin-coating technique, which is an easy, simple, and economical option to prepare films compared to other reported methods. According to the results obtained, the presence of CuO and Ag on the ZnO surface favored the better separation of the photogenerated electron–hole pair, as well as a better visible light absorbance compared to pure ZnO and CuO. The characterization of the films was carried out by X-ray diffraction and scanning electron microscopy techniques to know the structural and morphological parameters, respectively, while through UV–Vis analysis, it was possible to determine the bandgap energy value of the films through the Tau plot. Likewise, by means of photoluminescence analysis, it was possible to observe an improvement in charge transfer, thus avoiding the rapid recombination of the photogenerated electron–hole pair. Finally, photoelectrochemical tests (PEC) for photocurrent generation showed an improvement for the ZnO/CuO/Ag heterojunction film (0.78 mA/cm²), almost five times greater than ZnO (0.15 mA/cm²), respectively, which is caused by the increased electron transport that is linked to the longer lifetime of the charge carriers with an effective separation of the electron–hole pair and a fast diffusion rate.