Electrochemical growth and characterization of Cu2O:Na/ZnO heterojunctions for solar cells applications


Kara R., Lahmar H., Mentar L., Siab R., Kadırgan F. , Azizi A.

JOURNAL OF ALLOYS AND COMPOUNDS, cilt.817, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

Cu2O:Na/ZnO/FTO heterojunctions were successfully prepared by a simple two-step electrodeposition method. The effects of the doping concentration of Na on the electronic, morphological, microstructural, optical and electrical properties of the nanostructures were investigated. The deposition was carried out at various concentrations of Na ions and constant bath temperature (70C degrees). Cyclic voltammetry was utilized for the determination of the selective potential for electrodeposition of pure Cu2O. Mott-Schottky electrochemical impedance analysis showed p-type conductivity for the Cu2O layers and n-type conductivity for the ZnO films. X-ray diffraction analysis indicated that all doped and undoped Cu2O nanostructures have a polycrystalline nature with a highly cubic Cu2O (111) oriented crystallites and a hexagonal wurtzite structure of ZnO having (002) preferential orientations. Scanning electron microscopy and atomic force microscopy measurements point out the decrease of the grain size and the roughness of Cu2O:Na-x/ZnO heterojunctions with the formation of typical (111) textured feature, through the contribution of Na doping. From UV-Vis spectra, a red-shift of the bandgap from 2.223 to 2.008 eV with an increase in the optical conductivity range up to 9 x 10(14) cm(-1) was noted by increasing the Na content. The current-voltage characteristics of p-Cu2O:Na/n-ZnO heterojunctions showed excellent rectifying behavior, achieving a high rectifying ratio of 3133%. Na doping has been demonstrated by a huge drop in the series resistance of Cu2O/ZnO heterojunctions besides a great improvement in both of the ideality factor and the threshold voltages as well as photoelectric responses. The highlighted results are attractive and suitable for photovoltaic applications. (C) 2019 Elsevier B.V. All rights reserved.