Abstract
ZnO porous thin films were synthesized as antireflection coatings via a sol–gel dip-coating method with polyethylene glycol (PEG1000) utilized as a polymeric porogen on alumina transparent ceramics. The pore formation mechanism of the ZnO porous thin films was proposed through thermal and Fourier transformation infrared spectrometer (FTIR) analyses. The effect of sol concentrations on crystal structure, microstructure, and optical properties was also discussed. The experiment results indicated that all the ZnO thin films exhibited a hexagonal wurtzite structure with their preferred orientation along a (0 0 2) plane by X-ray diffraction (XRD) patterns. The grain size of the films increased from 30.5 to 37.4 nm with the sol concentration ranging from 0.2 to 1.0 M. Furthermore, scanning electron microscopy (SEM) images show that the pores on the surface were observed to first decrease as the sol concentration increased and then to disappear as the sol concentration continued to increase. The UV spectrum presents a maximum transmittance of 93.5% at a wavelength of 600 nm at a concentration of 0.6 M, which will be helpful in the practical applications of ZnO porous film on alumina transparent ceramic substrates. The pore formation mechanism of ZnO porous thin films can be ascribed to ring-like network structures between the PEG1000 and zinc oligomers under the phase separation effect.
Highlights
Antireflection (AR) coatings have many great applications in optoelectronic devices that require maximum light transmission such as solar cells and camera lenses [1,2]
zinc oxide (ZnO) porous thin films were successfully synthesized on alumina transparent ceramic substrates
ZnO porous thin films were successfully synthesized on alumina transparent ceramic substrates via the sol–gel method utilizing polyethylene glycol (PEG1000) as a polymeric porogen
Summary
Antireflection (AR) coatings have many great applications in optoelectronic devices that require maximum light transmission such as solar cells and camera lenses [1,2]. They can obviously reduce incident light reflection of the material surface and increase transmission. Searching for appropriate materials that can be used as antireflection coatings on ceramics is an efficient way to improve light transmittance. ZnO is a prospective and attractive material for many applications because it is a semiconducting material with a wide and direct band gap (3.37 eV) as well as a large exciton binding energy (~60 meV) [7]. In addition to its transparency in the visible range, the thermal stability of
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