Enhanced charge transport properties of Ag and Al co-doped ZnO nanostructures via solution process

Abstract

Conducting Ag and Al co-doped ZnO (ZnO:Al:Ag) nanostructures were synthesized using sol-gel process. The effects of Ag incorporation on the structural, optical, electrical, and photoluminescent properties of ZnO:Al:Ag nanostructures were studied. The crystalline quality of the nanostructures was found to be improved by Ag doping concentration of 0.3% owing to compensation for vacancies created by Al3+ via Ag+. The electrical properties were enhanced for Ag doping concentration of 0.3%. This may be due to an improvement of the crystalline quality. The optical band-gaps (Eg) of the nanostructures are significantly lower than that of undoped ZnO. The Eg of the nanostructures slightly decreased to its minimal value with Ag doping, and was found to be about 3.19 eV for RAg/Zn = 0.3%; the material then retained its initial value of 3.22 eV (RAg/Zn = 0%) for higher Ag doping. With Ag doping, the value of work function (WF) increased from 4.67 eV for RAg/Zn = 0% to 4.99 eV for RAg/Zn = 0.3% due to substitution of Ag+ into Zn2+ sites. An absorption peak in the blue region was observed in the Ag-doped nanostructures; this peak redshifted with the increase of the doping concentration. The photoluminescence (PL) intensity in the near band edge (NBE) region was the highest for the Ag/Zn ratio of 0.3%, whereas the maximum PL intensity in defect region was obtained for the Ag/Zn ratio of 0%. © 2016 Published by Elsevier B.V.