Effect of Zinc Acetate Concentration on Structural, Optical and Electrical Properties of ZnO Thin Films Deposited by Electrostatic Spray on an ITO Substrate

Abstract

Polycrstalline zinc oxide (ZnO) thin films were fabricated on indium tin oxide (ITO) substrates by electrostatic spray deposition using propylene glycol as the solvent for potential use in bulk heterojunction polymer solar cells. The microstructure and characteristics of the ZnO/ITO bilayer have been investigated for various precursor concentrations using SEM, AFM, X-ray diffraction, and UV-Visible spectroscopy. The bandgap energy of the bilayer slightly decreases when the zinc acetate dihydrate concentration in the propylene glycol solvent increases from 0.1 to 0.3 M. The ZnO/ITO bilayer shows high figure of merit (12.4 × 10 −3 −1 ) and low resistivity (3.78 × 10 −3 -cm) for a Zn precursor concentration of 0.2 M.Zinc oxide (ZnO) thin films form transparent conducting oxides because of their appropriate electro-optical properties such as a wide bandgap (3.25 eV), 1 large exciton-binding energy (60 meV) yielding effective excitonic UV emissions, and high optical gain (300 cm −1 ) 2 at room temperature. In addition, ZnO is inexpensive and non-toxic, which makes it attractive for many industrial applications 3 such as energy-efficient windows, liquid crystal displays, optoelectronic devices, ultrasonic oscillators, transducers, solar cells (a-Si, CIGS, inorganic thin film, and flexible polymer), gas sensors, 4 UV luminescence devices, light emitting diodes, 5 integrated optics, antireflection coatings, lasers diodes, UV range detectors, photodegradation, photocatalysis, superhydrophobic or self-cleaning surfaces, 2 and transistors. 6 ZnO thin films have been produced with various vacuum-based techniques, such as RF magnetron sputtering, 7 metal organic chemical vapor deposition, 8 plasma-assisted molecular beam epitaxy, 9 and pulsed laser deposition. 10 However, these techniques require expensive vacuum chambers yielding restrictive operating conditions (e.g., limited coating area); thus alternative techniques are needed. In general, sol-gel, 11 spray pyrolysis, 6 dip coating, 12 and electrostatic spray deposition (ESD) 13 are considered cost-effective alternative deposition methods. Among these, spray-based methods are preferred for coating large areas and ESD is particularly attractive because it produces extremely fine (sub-micron), self-dispersive (nonagglomerating), highly wettable (electrowetting) adhesive droplets that yield a uniform coating on the substrate; see Fig. 1a. In addition, because charged droplets are accelerated toward the substrate, ESD offers improved targeting, which results in high deposition efficiency and low material consumption. 14 Using the ESD aerosol technique, organic solvents containing inorganic or organometallic precursors can be dispersed into micrometer-sized, charge carrying droplets under an imposed electric field. 15 The precursor, containing dissolved salts (zinc acetate dihydrate in this case), is pumped through a metal nozzle, and high voltage (typically 6 to 15 kV) is applied between the nozzle (anode) and the grounded substrate (cathode). The fluid emerging from the tip ...

Role of Ethanolamine on the Stability of a Sol–Gel ZnO Ink

“…In most reports published so far, it is obtained by using zinc acetate dihydrate (ZAD) as the salt and ethanolamine (EA) as the stabilizer. The increasing interest in the development of sol–gel ZnO inks is reflected by recent specific studies on the effect of solvents, , precursor nature and concentration, , EA/ZAD molar ratios, , sol aging, annealing duration, , annealing temperature, , and even specific process parameters such as withdrawal speed in deep coating on the properties of the resulting ZnO.…”

Influence of zinc concentration on band gap and sub-band gap absorption on ZnO nanocrystalline thin films sol-gel grown

“…respectively. It implies the polycrystalline nature with hexagonal wurtzite structure of the films [20]. All the samples exhibit strong peak intensity along the (1 0 0) plane.…”

Progress in Spray Coated Perovskite Films for Solar Cell Applications

“…[12b] Heo et al have also fabricated planar-type CH 3 NH 3 PbI 3Àx Cl x PSCs via airbrush spray coating (Figure 6) using a carefully controlled solvent composition, resulting in unit cells with PCE values of 17.8% (forward scan), 18.3% (reverse scan), and 16.1 AE 1.3% (average) under 1 sun conditions. [12e] By employing solvents with differential vapor pressures, e.g., controlling the ratio of DMF (a relatively [40] Copyright 2012, The Electrochemical Society.…”

“…Figure 3. a) Procedure and b) schematic of the electrospray technique. Reproduced with permission [40]. Copyright 2012, The Electrochemical Society.…”