thesis

Hybrid Quantum Dot-Organic Solar Cells by Solution Processing

Abstract

Department of Energy EngineeringEnvironmental cleaned renewable energy resources such as solar energy have gained significant attention because of the continual enhancement in worldwide energy requirement. A variety of technologies have been developed to make the best use of solar energy. For instance, solar cells based inorganic materials such as silicon wafer can convert solar energy directly to an electricity energy, however inorganic materials are expensive to manufacture, and thus unattractive for general use. Therefore, many researchers have focused on the low cost and easy processing strategies are underway to confirm the materials and solar cells device architectures that are inexpensive efficient compared to inorganic solar cells such as silicon solar cells. Recently, solution processing thin film solar cells is highlighted and many researchers working on this field. Therefore, conjugated polymer based on the solar cells is rapidly growth and achieved power conversion efficiency (PCE) over 10% in single junction. And quantum dot solar cells (QDSCs) reported over 8% PCE at short period time. Here, I present positive effect on combination in the organic and quantum dot (QD) for solar cells application with all solution processing. First, The effect of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as a buffer layer was investigated in PSCs. Four different types of PEDOT:PSS were used: PH, PH500 and their DMSO-doped counterparts. The efficiency of PSCs was independent of the electric conductivity of the buffer layer as a bulk property. Second, the effect of ionic liquid molecules (ILMs) in QD-organic hybrid solar cells. The insertion of a ILMs layer between PbS QD and Phenyl-C61-butyric acid methyl ester (PCBM) can shift the band edge of the PCBM closer to the vacuum level of PbS. Owing to this new architecture, improvements in device performance were achieved. Third, new technique for preparing inverted colloidal QDSCs using layer-by-layer processed PbS QD and a ZnO layer formed via the solution-phase decomposition of diethyl zinc directly on the PbS film. The inverted QDSCs enhanced in device characteristics stem from constructive optical interference in the absorbing PbS QD layer, as well as outstanding diode characteristics arising from a superior PbS/ZnO junction achieved substantial improvements in short-circuit current, open circuit voltage, fill factor and PCE relative to a control device. Fourth, new types of architecture of hybrid QD-organic solar cells (by introducing PbS QD layer as performing role of photo sensitized layer to achieve high Jsc and PCE using NIR region up to 1100 nm from PbS QD light absorbed.ope

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