Influence of Post Annealing Rates on Porosity, Dispersion Energy and Associated Dielectric Energy Losses of TiO2 Thin Films
Nelson Mugambi,
James Mbiyu Ngaruiya,
Simon Waweru Mugo,
Geoffrey Gitonga Riungu,
Gitonga Mbae John
Issue:
Volume 7, Issue 1, June 2021
Pages:
1-7
Received:
20 December 2020
Accepted:
18 January 2021
Published:
25 January 2021
Abstract: With scientific and technological advances, Titanium dioxide (TiO2) has attracted great research interest in the field of Dye Sensitized Solar cells (DSSC) with an aim to improve its efficiency. In this study, transparent semiconducting titanium dioxide thin films were deposited on glass substrate coated with fluorine tin IV oxide (SnO2: F) film by sol gel technique. The films were then annealed in air up to 450°C at different annealing rates. Optical reflectance was measured using UV-Vis-NIR spectrophotometer and optical parameters such as refractive index, extinction coefficient and dielectric constants were modelled using SCOUT software. Average refractive indices in the visible region ranged between 1.95 and 1.56. Porosity for as deposited, 1 step, 2°C/min and1°C/min were found to be 48%, 73%, 61% and 53% respectively. Refractive index dispersion was investigated using Wemple – Di-Domenico single oscillator model. Dispersion energy of annealed films increased from 5.90 eV to 11.30 eV. Surface and volume energy loss were computed from dielectric constants and correlated with porosity and dispersion energy as function of the heat treatment. Optical parameters were found to highly depend on the annealing the thin films. Annealing rate influenced a decrease in porosity and an increase in dispersion energy due to film densification and pore filling as the crystallinity is improved by heat treatment.
Abstract: With scientific and technological advances, Titanium dioxide (TiO2) has attracted great research interest in the field of Dye Sensitized Solar cells (DSSC) with an aim to improve its efficiency. In this study, transparent semiconducting titanium dioxide thin films were deposited on glass substrate coated with fluorine tin IV oxide (SnO2: F) film by...
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High Optical Reflection in Two-dimensional ZnO-Si Photonic Crystals Induced by Coupled Optical Micro-cavities
José Antonio Medina-Vázquez,
Evelyn Yamel González-Ramírez,
José Guadalupe Murillo-Ramírez
Issue:
Volume 7, Issue 1, June 2021
Pages:
8-15
Received:
21 June 2021
Accepted:
5 July 2021
Published:
9 July 2021
Abstract: Photonic crystals can exhibit relevant optical properties when transmitting or reflecting a light beam. In particular in a two-dimensional photonic crystal the reflective properties can be of interest and consequently optimized for different technological applications such as tunable laser cavities, photovoltaic solar systems, and selective high reflection mirrors among many others. Taking this motivation into account, a study of the reflective optical properties of two-dimensional photonic crystals built on a hybrid substrate of ZnO:Si has been developed. The aim of the present research is to demonstrate the feasibility to control the optical reflectance spectra of a two-dimensional photonic crystal by the inclusion of an array of optical micro-cavities in a regular photonic structure. Moreover, in this research an explanation of the origin of the high optical reflectance predicted by numerical calculations and confirmed by experimental measurements in a photonic crystal that contains an array of micro-optical cavities is also given. The results of numerical calculations of the optical properties of one of the photonic crystals studied determined that the origin of the increase in its optical reflectance is the light emission from the silicon present in the ZnO-Si substrate where the photonic structure was built. Strong resonant modes of the optical electric field stablished mainly in silicon present in two types of resonant cavities recognized in the photonic crystal favor the stimulated emission of light that gives rise to the high optical reflectivity.
Abstract: Photonic crystals can exhibit relevant optical properties when transmitting or reflecting a light beam. In particular in a two-dimensional photonic crystal the reflective properties can be of interest and consequently optimized for different technological applications such as tunable laser cavities, photovoltaic solar systems, and selective high re...
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