On the Development of Colloidal Quantum Dot Sensitized Solar Cell Architectures
Ghada Hamdi Mohamed Ahmed
- 2014
- p. ill. 21 cm.
Supervisor: Mohamed Sabry
Thesis (M.A.)—Nile University, Egypt, 2014 .
"Includes bibliographical references"
Contents: Nanotechnology and solar energy Solar cells and photovoltaic generations First generation solar cells Second generation solar cells Third generation solar cells Organic solar cells Dye sensitized solar cells Quantum dot sensitized solar cells Structure and design Working mechanism Methods for fabrication of the QDSSC photoelectrodes Recently proposed Pseudo-SILAR solar paint Our Novel proposed physical mixing method QDSSC characterization and performance parameters Motivation and Literature Review Why Quantum dots as sensitizers? Multiple Exciton Generation . Cadmium Selenide (CdSe Zinc Oxide (ZnO An Overview of the Dissertation work CHAPTER 2: EXPERIMENTAL PROCEDURE AND CHARACTERIZATION Instrumentation The prepared nanomaterials Transmission Electron Microscopy (TEM Absorption and Fluorescence spectra X-ray Diffraction Thin film Characterization SEM Optical measurements of thin films The sensitized solar cells (Fabrication and Characterization Needed Devices 2.2.3.1. Spin coater 2.2.3.2. Muffle furnace for thin film annealing 2.2.3.3. Keithley source meter 2.2.3.4. Solar simulator 2.3. Methodology 2.3.1. Preparation of ZnO and Au-ZnO nanocones by microwave irradiation method 2.3.2. Preparation of CdSe quantum dots by organometallic pyrolysis method 2.3.3. Preparation of the polysulphide electrolyte 2.3.4. Fabrication of ZnO or Au-ZnO/ CdSe based electrodes 2.3.5. Detailed fabrication steps for mixed and layer-by-layer method CHAPTER 3: RESULTS AND DISCUSSION 3.1. The Prepared nanomaterials (TEM, Absorption- photoluminescence, and XRD 3.1.1. Characterization of ZnO nanopyramids 3.1.2. Characterization of Au-ZnO nanopyramids 3.1.3. Characterization of CdSe quantum dots 3.2. The prepared thin films: (Optimization, Optical characterization and SEM 3.2.1. Optimization 3.2.2. SEM and surface morphology 3.2.3. Optical measurements 3.3. The constructed solar cells (Solar cell performance
Abstract: Quantum dot sensitized solar cells (QDSSCs) have attracted a widespread attention over the past few years as a prospects of fabricating highly efficient, low cost third generation photovoltaics. Quantum dots (QDs) –The light harvesting material in the solar cell– such as CdSe, CdTe and CdS exhibit size-dependent band gaps which offer great opportunities for harvesting light energy in the visible and infrared regions of the solar spectrum. In addition, due to impact ionization effect, it is possible to utilize hot electrons in QDs to generate multiple electron–hole pairs per photon of light absorption. These features give to QDSSCs the capability to achieve conversion efficiencies beyond the Shockley– Queisser limit, and provide a transformative improvement to traditional silicon photovoltaic cells. Currently available QDSSCs fabrication procedures utilize a series of deposition steps to achieve a better performing photoanode. Semiconductor film deposition and annealing techniques are time-consuming processes, requiring multiple steps and several days to achieve the best performing photoelectrode. In order to produce more functional and economically viable QDSSCs, it is important to simplify the electrode preparation techniques. Therefore, this study presents a novel method for casting the quantum dot onto the semiconductor based electrode by directly mixing the photoanode components together without a molecular linker, which offers easier scaling up process while maintaining a very low cost. This method was compared with layer-by-layer method and showed an improvement in the overall cell performance parameters. In addition, this work focuses on applying uniform-sized hexagonal pyramid-shaped ZnO and Au-ZnO nanoparticles for the first time in QDSSCs. The as-prepared nanoparticles possess excellent optical, catalytic and electrical properties. Furthermore, another Au nanoparticles layer/ZnO based QDSSC was constructed and compared with Au-ZnO hybrid structure in order to figure out the plasmonic effect of Au nanoparticles on the QDSSC light absorption behavior. xviii The results showed that the cells incorporating the Au nanoparticles layer/ZnO electrode exhibited the highest cell efficiency of = ~0.1% compared to other cells based on bare ZnO or Au-ZnO hexagonal nanopyramid-shaped. The results also suggest that metal nanoparticles (NPs) are potentially useful for improving the photoresponse in QDSSCs. However, for effective charge separation, these metal (NPs) should be isolated or separated from the wide band gap material and the sensitized material.