Low-cost thin-film deposition apparatus for solar applications

Widespread adoption of solar energy technologies, such as solar photovoltaics (PV) and/or photoelectrochemical (PEC) hydrogen fuel production cells, requires low-cost fabrication methods to produce large area devices for solar energy harvesting. Novel thin-film semiconductor materials produced from chemical solution deposition have significant potential to reduce production and manufacturing costs. Ongoing research at James Madison University is focused on the development and fabrication of thin-film semiconductor materials for PV and PEC applications. Thin-film semiconductors, such as BiVO₄ and Cu₂ZnSnS₄, are fabricated by depositing a liquid precursor solution onto a heated substrate using ultrasonic spray pyrolysis, pneumatic spraying, or liquid drop casting. To enable thin-film depositions over larger sample areas, an automated deposition system is being developed. This coating system is comprised of two primary and interacting subsystems: motion and heating control. The motion system controls the path and travel speed of the precursor deposition device, such as the ultrasonic spray nozzle, during the deposition process. During the deposition procedure, the substrates rest on a heated surface, which provides the energy necessary to induce the desired chemical reactions on the substrate and remove unwanted compounds. This surface have a uniform spatial temperature distribution and must be controlled to a constant temperature ranging from 40 °C to 500 °C with a variability of ±4 °C. A specially designed heating plate was designed to meet these requirements. The focus of this work is to design an integrated system that allows a deposition area of 16 in² to be completed at James Madison University.