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Download or read book Development of Earth-abundant Materials and Low-cost Processes for Solar Cells written by Chih-Liang Wang and published by . This book was released on 2014 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of renewable solar energy research is to develop low-cost, high-efficiency photovoltaic technologies. However, with the growing deployment of solar cells, approaching the terawatt scale, absorber materials reliant upon rare or unfriendly elements become a crucial issue. Thus, the primary objective of this dissertation is the development of a low-cost fabrication method for (i) thin-film solar cells and (ii) dye-sensitized solar cells using earth-abundant materials. In thin-film solar cells, the kesterite Cu2ZnSnS4 with earth abundant elements is used as an absorber layer. It possesses a high absorption coefficient, direct band gap, and good long-term stability compared to the traditional CdTe and Cu(In,Ga)(S,Se)2 (CIGS) absorber layers. A facile hot-injection approach for synthesizing Cu2ZnSn(S,Se)4 nanocrystals with varied Se to (S+Se) ratio is developed to systematically investigate the role of Se in Cu2ZnSn(S,Se)4 nanocrystals and the evolution of Cu2ZnSn(S,Se)4 nanocrystals to Cu2ZnSn(S,Se)4 film during the sulfurization step to address the problems associated with its narrow compositional window and the loss of Sn during heat treatment. Additionally, the existing substrate-type device configuration for these solar cells uses a molybdenum (Mo) back contact, which suffers from serious disadvantages like the (i) presence of a Schottky barrier at the Mo/Cu2ZnSn(S,Se)4 interface and (ii) decomposition of Cu2ZnSn(S,Se)4 at the Mo interface. Accordingly, a low-cost and Mo-free superstrate-type device configuration of Au/Cu2ZnSn(S,Se)4/CdS/TiO2/ITO/glass is developed to evaluate the conversion efficiency and to avoid the occurrence of a Schottky barrier at the interface and potential decomposition pathways induced by the formation of Mo(S,Se)2. Furthermore, with the addition of ethyl cellulose, the loss of Sn associated with the conversion of CZTSe to CZTSSe during the grain growth process is mitigated, leading to an increase in the conversion efficiency compared to that of the precursor film without using ethyl cellulose. Such an improvement can provide insight into the grain growth of CZTSSe during the sulfurization process and thereby enhance the feasibility of sustainable, high efficiency CZTSSe solar devices. The excellent characteristics of dye-sensitized solar cells (DSSCs) with short energy-payback time, simple assembly, and eco-friendly features make them a potential option to utilize solar energy. Accordingly, a facile, low-cost, template-free route for TiO2 hollow submicrospheres embedded with SnO2 nanobeans is developed for use as a versatile scattering layer in DSSCs. Our designed structure simultaneously promotes dye adsorption, light harvesting, and electron transport, leading to a 28 % improvement in the conversion efficiency as compared with the film-based SnO2. In addition, a naturally-derived carbonaceous material as a Pt-free counter electrode for DSSCs is also developed for the first time: carbonized sucrose-coated eggshell membrane (CSEM). It is found that the carbonized sucrose-coated eggshell membranes consist of unique micropores of less than 2 nm, which effectively catalyze the triiodide into iodide in the light-electricity conversion process, leading to an improvement in the V [subscript oc] and a competitive efficiency as compared to that of a DSSC with a traditional Pt-based counter electrode.