Comparative studies of structural and electrical properties of co-doped ZnO thin films prepared by direct current sputtering as a front contact for copper indium gallium di-selenide solar cell

Abstract

Doped and co-doped ZnO thin films are currently under intense investigation and development for optoelectronic and solar cell applications. Here in this study Aluminum and Boron (ZAB), Gallium and Boron (ZGB), and Gallium and Aluminum (ZGA) co-doped ZnO thin films were deposited on glass substrate using DC magnetron sputtering at room temperature. A comparative study of the above co-doped ZnO thin films was done on the basis of its structural and electrical properties for solar cell application. All thin films have shown excellent optical properties with more than 80% transmission in the visible range of the light. From the X-ray diffraction patterns, it is found that the films were polycrystalline in nature and the ZAB thin film is more crystalline than the other co-doped ZnO thin films. The surface morphology showed different growth structure of the films. For ZAB and ZGA thin films, the rounded grains were observed and for ZGB thin film some rounded as well as corn type grains were observed. The electrical properties of all the thin films were measured using Hall measurement system at room temperature. For ZGB and ZGA thin films, the resistivity was obtained in the order of 10−3 ohm cm and for ZAB thin film the lowest resistivity of the order of 10−4 ohm cm was obtained which is ideal for transparent conducting oxide thin films to be used as window cum-front contact in multi-junction solar cell such as CIGS solar cell.