Development of Pb and Cd chalcogenide nanomaterials, nanocomposites and thin films : synthesis, characterization and applications in solar cells and photocatalysis

Authors: Patel, Jayeshkumar Dineshbhai
Advisor: Mighri, FrejAjji, Abdellah
Abstract: Metal chalcogenides have emerged as an important class of materials due to their potential significance in many technological applications. In this work, easy and low cost approaches have been developed to prepare metal chalcogenide nanomaterials and thin films from their metal-organic complex precursors. The use of synthesized nanomaterials and thin films in solar cells and photocatalytic water purification has been discussed. The first approach adopted involves the synthesis of metal sulphide nanomaterials using metal-thiourea (M-TU) complex precursors. Lead sulphide (PbS) nanocrystals (NCs) and nanostructures were synthesized from methanolic lead-thiourea (Pb-TU) complex via various precipitation techniques based on the decomposition of methanolic Pb-TU complex. We have also synthesized cadmium sulphide (CdS) nanostructures through hydrothermal and solvothermal treatment of aminocaproic acid (ACA)-mixed cadmium-thiourea complex precursor. The as-synthesized CdS nanostructures were found to exhibit highly efficient photocatalytic activities for the degradation of methyl orange and rhodamine B (RhB) in aqueous medium. We have also developed simple synthetic routes to prepare metal chalcogenide nanomaterials from metal-oleate (M-O) complexes. Sulphurizations of M-O complex precursors at relatively low temperatures produced highly stable metal sulphide NCs because oleic acid (OA) is chemisorbed as a carboxylate onto the surface of NCs. The cadmium-oleate (Cd-O) complex precursor was also used to prepare CdSe NCs. Surface treatments of the as-synthesized CdSe NCs with pyridine and tert-butylamine were very effective to replace long chain OA ligands. Bulk-heterojunction solar cells made from surface treated cadmium selenide (CdSe) NCs showed greater improvement in photovoltaic performances compared to those made from untreated CdSe NCs. Solvothermal decomposition of thiourea-mixed Cd-O complex precursor also produced nanocrystals composed of cauliflower-like CdS microspheres with good physicochemical properties and photocatalytic ability to degrade RhB in aqueous medium. The spin-coating deposition technique was used to develop PbS and CdS thin films from their methanolic M-TU complex precursors. The obtained films had smooth surface and showed size quantized band gaps. The possible reasons behind the low efficiency of CdS/PbS thin film solar cell device were also discussed.
Document Type: Thèse de doctorat
Issue Date: 2014
Open Access Date: 20 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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