Fine Tuning of Photoluminescence Characteristics of Al2O3-doped TiO2:ZnO Nanocomposites Synthesized by Pulsed-Laser Deposition

This work systematically investigates the fine-tuning of optical absorption, energy band gap, and photoluminescence (PL) characteristics of Al2O3-doped TiO2:ZnO thin films prepared by pulsed-laser deposition (PLD) as a function of varying alumina weight percentages from 0.0 to 1.5 wt.%. The absorption spectra reveal a monotonic decrease in absorbance with increasing Al2O3 content attributed to the Burstein–Moss band gap widening and effective passivation of sub-bandgap defect states. The energy band gap exhibits a remarkable linear widening from 3.39 eV for the undoped film to 3.825 eV at the highest doping level, confirming the homogeneous incorporation of Al3+ ions and the successful engineering of the electronic structure through quantum confinement and alloying effects. Most notably, the photoluminescence spectra demonstrate a dramatic enhancement in emission intensity upon aluminum introduction as Al2O3 doping effectively passivates quenching defects while simultaneously creating new emissive states, thereby offering a powerful strategy for tuning the luminescence yield without compromising the structural integrity of the host matrix. These findings establish a comprehensive framework for understanding the intricate interplay between dopant concentration, defect chemistry, and radiative recombination dynamics in ternary oxide nanocomposites, positioning the Al2O3-doped TiO2:ZnO system as a highly promising candidate for applications in solid-state lighting, UV photodetectors, luminescent solar concentrators, and other advanced optoelectronic devices where precisely controlled emission characteristics are paramount.