Green Synthesis of ZnO Thin Films via Spray Pyrolysis: Electrochemical and Photocurrent Performance Analysis

This study presents the bio-synthesis of Zinc Oxide (ZnO) thin films using a spray pyrolysis technique with extract of Eucalyptus tree leaves as a precursor. The films were deposited onto copper substrate and characterized to investigate their structural, morphological, and electrochemical properties. Atomic Force Microscopy (AFM) revealed a uniform and well-dispersed ZnO layer across the surface of the electrode, while Scanning Electron Microscopy (SEM) analysis indicated the presence of a lamellar structure in the ZnO film. The electrochemical performance of the ZnO thin films was evaluated in a 0.1 M KCl electrolyte solution. The interface has been modeled using an equivalent circuit comprising of a parallel charge transfer resistance R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CT</inf> and a constant phase element (CPE) in series with a resistance of electrolyte R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</inf>. Through capacitance measurements and Mott Schottky analysis provided insights into the semiconductor–electrolyte interface by varying applied dc potential and frequency. Moreover, the carrier concentrations N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf> and flat band potentials V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fb</inf> of the sample were obtained by Mott-Schottky analysis. Furthermore, the photoelectrochemical performance of ZnO thin film was assessed and indicated that the maximum photocurrent density (9.041 mA/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) under light illumination, highlighting their excellent photocurrent transmission capabilities.