Room temperature photoluminescence of spray-deposited ZnO thin films on glass substrates

Abstract

The transparent conducting zinc oxide (ZnO) is of potential use in solar cells. Undoped ZnO thin films were deposited by the spray pyrolysis (SP) technique on glass substrates at 350 ± 5 °C using aqueous zinc chloride solution. The photoluminescence (PL) spectra of the films were measured at room temperature using three excitation wavelengths: 230, 300, and 360 nm. The sharp exhibited PL emission features in the ultraviolet (UV) and visible regions (VIS) of the prepared films are compared to those in powdered form reported in the literature. In the studied films, the 230 nm excitation wavelength enabled the observation of the PL signal in the range 330–470 nm, where the 300 and 365 nm excitation wavelengths enabled the registration of the PL signal in the wavelength range 330–570 nm. Moreover, it was found that the strongest PL signal was recorded using the 230 nm excitation wavelength under which sharp peaks in the UV and blue regions were observed. Weaker PL peaks in the UV and visible regions were recorded using the other two excitation wavelengths. Second derivative of the PL curves were used to detect the peaks. Peaks in the UV region are related to near-band-edge (NBE) transitions, and those in the VIS region are related to defects and impurities in the material. Hence, the acquired results based on the utilized techniques can be used to monitor the purity and quality of the prepared films and their characteristics.