Understanding scalable photovoltaics through liquid deposited nanoparticle precursors

Bryce C Walker, Purdue University

Abstract

Solar energy through photovoltaics is an abundant resource, but its feasibility as a major player in the energy landscape will rely heavily on being able to reduce costs through economies of scale. Despite this fact, current production methods are batch oriented, and suffer from poor scalability. Liquid-based semiconductor deposition methods are a promising concept being investigated throughout the world wherein the processes can be scaled. One particular liquid-based deposition method of interest is through the deposition of an ink of semiconducting nanoparticles in suspending solvents. The use of nanoparticle precursors is advantageous since it enables film homogeneity, solution deposition processes, flexibility in substrate choice, and fast processing times. The end result of these advantages is a process that is scalable. Nanoparticle based solar cells pioneered at Purdue University lead the world in this research. The technology relies on the formation of sulfide nanoparticles that are subsequently reacted in a selenium vapor rich environment leading to the formation of a densified selenide thin film. With this process, solar cells can be created from both Copper Indium Gallium Selenide (CIGSe) and the more earth abundant Copper Zinc Tin Sulfide/Selenide (CZTSSe). Due to the great capabilities of this process, many questions have been raised relative to nanoparticle synthesis and film formation, as well as the relationship between the two processes. Presented herein are the results of analyzing the dependencies of nanoparticle synthesis through ex-situ means as well as understanding the film formation through both ex-situ as well as real-time synchrotron-based in-situ energy-dispersive x-ray diffraction (EDXRD). The real-time analysis allows us to probe the basic structure of the film, and watch as the compounds successfully transform from their respective sulfide particles through various intermediates en route to the final selenide film. The insight obtained has allowed hypothesis to be challenged, alternative methods for crystal grain growth, and guided research to increase performance of thin film solar cells from deposited semiconducting nanoparticles.

Degree

Ph.D.

Advisors

Agrawal, Purdue University.

Subject Area

Alternative Energy|Nanoscience|Nanotechnology

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