COMPARISON OF OPTICAL AND STRUCTURAL PROPERTIES OF UNDOPUTED AND AL-DOPPED ZNO THIN FILMS OBTAINED BY SPIN COATING TECHNIQUE

Abstract

ABSTRACT

With the influence of economic conditions and environmental factors, the search for alternative energy sources has gained an important place in the scientific world. Energy consumption has inevitably increased, and the improvement in the quality of synthesis techniques depends on developments in science and technology. Sunlight is the cleanest and most abundant renewable energy source, converted into thermal or electrical energy by solar cells. Transparent conductive oxide (TCO) thin films are widely used on the front side of solar cells due to their favorable electro-optical properties. Nontoxic TCOs such as ZnO (pure and doped) have received outstanding attention for adaptive electronic applications.

Pure and Al-doped ZnO thin film at different ratios was produced on soda-lime glass with a low volume solution using the sol-gel spin coating technique, which is a cost-effective and simple method. Crystalline thin film layers were obtained at the optimum annealing temperature of 700 ⁰C for 1 hour. Optical transmittance and structural properties were investigated by systematically comparing pure and Al-doped thin films at different ratios. It has been observed that Al-doped ZnO thin films exhibit a preferential orientation along the (002) diffraction plane. The influence of Al doped atoms led to the rearrangement of the ZnO lattice structure and promoted grain growth. Therefore, the grain boundary between the grains decreased and the irregularities and defects in the lattice decreased.

Optical transparency and critical production parameters, which exhibit a transmittance of over 85% in the visible range, have shown a suitable investment opportunity with the commercialization of ZnO thin film obtained by sol-gel spin coating technique. Due to increasing Al concentration, the UV absorption edge of the films showed a blue shift, which caused the energy band gap to widen. Structural and microelectronic properties were analyzed by XRD. As a result of XRD analysis, it was seen that ZnO:Al exhibited hexagonal wurtzite crystal structure. Due to the increasing Al concentration, the crystallinity of the film decreased slightly due to the difference between the diameters of the atoms. On the other hand, as the annealing temperature increased, the grain boundaries between the particles decreased.

In this study, a more efficient use of ZnO thin films in microelectronic devices and solar energy systems and a relatively more cost-effective coating technology were investigated.