Optical and photoluminescent properties of sol-gel Al-doped ZnO thin films

Al-doped zinc oxide (AZO) thin films have been prepared via a sol-gel process. Optical and photoluminescent properties of the AZO films have been investigated. The UV absorption edge was blue shifted with increasing Al doping concentration. Efficient green–yellow emission was obtained after annealing at 850 °C. For the 850 °C-annealed samples, the green peak was red shifted from 518 to 565 nm as the Al doping concentration increased from 0 to 2.0 at.%. In addition, violet emission in the range of 400–450 nm was observed in the 850 °C-annealed AZO films. The possible origins responsible for these emission bands have been discussed.