Synthesis and Characterization of Earth Abundant and Nontoxic Metal Chalcogenides Produced via Aerosol Spray Pyrolysis for Photovoltaic Applications
A novel synthesis technique for the production of copper zinc tin sulfide (CZTS) nanocrystals has been developed using aerosol spray pyrolysis. CZTS is a quaternary semiconducting material that shows promise as a replacement to common semiconductors such as CdTe and CIGS for use in photovoltaic devices. CIGS is currently being commercialized in the photovoltaic industry, but rare and expensive indium and gallium components threaten its long term viability. CZTS looks to be one of the best alternatives to CIGS with all earth abundant and non-toxic materials and recent impressive gains in efficiency. A number of synthesis techniques have been thoroughly studied and detailed previously. In our novel approach, we synthesis single phase nanocrystals, starting with zinc, copper, and tin diethyldithiocarbamate precursors in a toluene solvent. The precursor solution is aerosolized using an ultrasonic nebulizer wherein the droplets are vacuumed through a tube furnace and nucleation occurs. We reproducibly synthesize kesterite, Cu2ZnSnS4, nanocrystals. This technique continuously converts the chemical precursor into high-purity nanopowder with a production rate of ~50 mg/hour for an un-optimized, lab-scale reactor. Using the same precursor chemistry, we have also been able to deposit high-quality CZTS thin films directly onto Mo-coated Swiss glass substrates using the aerosol spray pyrolysis technique. A thorough discussion of the current photovoltaic field, the processing parameters and challenges of nanocrystal and thin film production, and the experimental results will be presented. Characterization via Raman spectroscopy, EDS, XRD, TEM and XPS will be offered along with future recommendations and considerations.