A drastic improvement in the power factor of Al-doped ZnO (AZO) thin film was achieved by introducing Ti as a co-dopant with Al. A Ti super-thin buffer layer was firstly deposited on the glass substrate, and then AZO thin films were deposited onto Ti buffer layer at room-temperature. The introduction of Ti buffer layer facilitated the growth of AZO films and improved its crystallinity. XPS and XRD results showed that Ti4+ substituted for Zn2+ site, which created extra electrons. Dual doping of ZnO with Al and Ti drastically increased the electrical conductivity and the Seebeck coefficient of AZO films at high temperature. As a result, a significant enhanced power factor as high as 12.8 x 10(-4)Wm(-1) K-2 was achieved at 573 K in Ti co-doped AZO films, which was more than 18 times larger than that of the films without Ti co-doping (0.64 x 10(-4)Wm(-1) K-2). (C) 2017 Elsevier Ltd. All rights reserved.