Effect of solvents on sol–gel spin-coated nanostructured Al-doped ZnO thin films: a film for key optoelectronic applications

Aluminum-doped zinc oxide (AZO) thin films were deposited by sol–gel spin coating technique onto the glass substrates using different solvents such as 2-methoxyethanol, methanol, ethanol and isopropanol. Prepared films were characterized by XRD, Raman spectrum, SEM, UV–visible spectrophotometer, photoluminescence (PL) and electrical studies. XRD studies showed that all the prepared films are hexagonal wurtzite structure with polycrystalline nature oriented along (002) direction. SEM images showed uniform particles of size around 60 nm distributed regularly on to the entire glass substrate. EDX analysis confirmed the composition of grown AZO film consisting of Al, Zn and O elements. The prepared films showed highest optical transmittance ~ 94% in the visible range and band gap 3.30 eV. PL spectra for all AZO films showed a strong UV emission peak at 387 nm. The AZO films prepared using isopropanol solvent showed high carrier concentration and low resistivity values as 1.72 × 10²⁰ cm⁻³ and 2.90 × 10⁻³ Ω cm, respectively, with high figure of merit (ϕ) value 8.42 × 10⁻³ (Ω/sq)⁻¹.