SYNTHESIS AND CHARACTERIZATION OF CdO THIN FILMS BY SUCCESSIVE IONIC LAYER ADSORPTION REACTION (SILAR) METHOD USING TWO DIFFERENT COMPLEXING AGENTS

CHAPTER ONE

         1.1 General Introduction

The sun releases an estimated 10¹⁷ Joules of energy, which it delivers to earth in one second [1]. Earth’s ultimate recoverable resource of crude oil, estimated at 3 trillion barrels, contains 1.7×10²² joules of energy, which the sun supplies to earth in 1.5 days [1]. The amount of energy humans use annually, about 4.6×10²⁰ Joules, is delivered to earth by the sun in one hour [2]. The enormous power that the sun continuously delivers to earth is 1.2×10⁵ terawatts (TW), dwarfs every other energy source [2], renewable or non renewable. It dramatically exceeds the rate at which human civilization produces and uses energy, currently about 13TW [3]. The impressive supply of solar energy is complemented by its versatility. Sunlight can be converted into electricity by exciting electrons in a solar cell. It can yield chemical fuel via natural photosynthesis in green plants or artificial photosynthesis in human-engineered system’s [4] Concentrated or unconcentrated sunlight can produce heat for direct use or further conversion to electricity. Despite the abundance and versatility of solar energy, we use very little of it to directly power human activities. Solar electricity accounts for a minuscule 0.015% of world electricity production, and solar heat for 0.3% of global heating of space and water [5]. Biomass produced by natural photosynthesis is by far the largest use of solar energy; its combustion or gasification accounts for about 11% of human energy need [6].              However, more than two-third of that is gathered unsustainably, that is, with no replacement plan and burned in small, inefficient stores where combustion is and the resulting pollutants are uncontrolled.

Between 80% and 85% of world energy comes from fossil fuels, a product of ancient biomass stored beneath earth’s surface for up to 200 million years [7]. Fossil fuel resources are of finite extent and are distributed unevenly beneath earth’s surface. When fossil fuels are converted into useful energy through combustion they produce green house gases and other harmful environmental pollutants. In contrast, solar photons are inexhaustible and unrestricted by geographical boundaries. Their direct use for energy production does not threaten heat or climate. The solar resources, magnitude, wide availability, versatility and benign effect on the environment and climate make it an appealing energy source. It is anticipated that by the year 2030 the world demand for electricity will double and the demands for fuel and heat will increase by 60% [7]. The utilization gap between solar energy’s potential and our use of it can be overcome by raising the efficiency of the conversion processes.

The use of photovoltaic (PV) modules for electricity generation has come under intensive research in recent times, with a view to increasing the efficiency and reducing investment capital [8]. Generating significant fraction of future energy requirement from PVs is a major challenge to solar energy physicists [9], particularly because present PV production is almost insignificant relative to fossil fuel-based generation [10].

        1.2   Purpose of the Study

The purpose of the study is to:

• deposit cadmium oxide (CdO) thin film on glass substrate using the Successive Ionic                               Layer Adsorption and Reaction techniques (SILAR), for two complexing agents,NH₃ and NaOH.
• characterize the deposited CdO films using the UV/VIS/NIR spectroscopy.
• investigate the effects of the number of cycles on the band gaps of the deposited CdO thin film.
• study the variation between the optical conductivity and the band gap energy of the film.
• determine the relationship between the dielectric function of the material and the band gap energy and number of cycles.
• investigate the effect of complexing agents on deposition of CdO films.
• to study the structural properties of the deposited films.

         1.3 Scope of the Study

This research work is limited to the growth and characterization of CdO thin films grown on glass substrate using SILAR technique. The deposition of CdO will be carried out using ammonia (NH₃) and sodium hydroxide (NaOH) as  complexing agents.

DOWNLOAD COMPLETE PROJECT