Synthesis and characterization of Zinc Oxide thin films deposited by Spray Pyrolysis technique for possible applications in solar cells

Abstract

In the present study, the synthesis and characterization of ZnO thin films deposited at 300, 350 and 400°C using the Ultrasonic Spray Pyrolysis technique, as a possible candidate for electron transport layer (ETL) in solar cells is reported. X-ray diffraction (XRD) analysis revealed that the films have a hexagonal wurtzite phase with a preferential orientation (101) with good polycrystallinity. The mean crystallites size based on the Debye-Scherrer model was calculated, indicating that the size of the crystals decreases as the deposition temperature increases. The optical characterization of the material showed a high transmittance in the visible region (85-99%) with which the optical band gap (3.06-3.29 eV) was determined. The thickness, surface roughness and optical constants (n and k) were determined by Spectroscopic Ellipsometry using the Gaussian oscillator model. Hall Effect revealed a low resistivity of 1-4 Ω cm and a high mobility of charge carriers (304 cm2/Vs) in the films. Due to all these properties, ZnO is considered an ideal material for optoelectronic applications, as well as a material with potential to be used as ETL in solar cells.