Effects of the Ho3+/Yb3+ concentration ratio on the structure and photoluminescence of ZnO films

• Published in: Journal of luminescence Vol. 175; pp. 78 - 81
• Main Authors: Xu, Boxu, Wang, Pei, Meng, Xiaoqi, Zou, Kaishun, Liu, Juncheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2016
• Subjects: Ho3+/Yb3+ concentration ratio; Photoluminescence; Sol–gel; Up-conversion; ZnO film; ZnO film; Ho3+/Yb3+ concentration ratio; Sol–gel; Up-conversion; Photoluminescence
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2016.02.014

To improve the efficiency of photoluminescent films, this study investigates the effects of the Ho3+/Yb3+ concentration ratio on the structure and up-conversion photoluminescence of ZnO films prepared by the sol–gel method and the spin-coating technique. ZnO maintained its hexagonal wurtzite structure after doping with rare earth ions. The ZnO films consist of round granules, the average size of which increases as the Ho3+/Yb3+ concentration ratio increases. Once the ratio exceeds 1:2, the film׳s granules significantly coarsen, and the surface roughness slightly increases. When the film is pumped with a 980-nm laser, two intense emission bands are observed in the up-conversion emission spectrum, with a green band centered at 550nm and a red band centered at 660nm, corresponding to the Ho3+: 5S2/5F4→5I8, and 5F5→5I8 transitions, respectively. In addition, as the Ho3+/Yb3+ concentration ratio increases, the intensity of the film׳s upconversion luminescence first increases and then decreases, reaching a maximum at a concentration ratio of 1:2, with a peak of about four times the minimum value.