A machine learning system promises to speed up production of perovskite-based solar cells. (Image: Photo of solar cell by Nicholas Rolston, Stanford, and edited by MIT News. Perovskite illustration by Christine Daniloff, MIT)

Perovskites are a family of materials that are currently the leading contender to potentially replace today’s silicon-based solar photovoltaics. Manufacturing perovskite-based solar cells involves optimizing at least a dozen or so variables at once, even within one particular manufacturing approach among many possibilities. But a new system based on a novel approach to machine learning could speed up the development of optimized production methods and help make the next generation of solar power a reality.

The system, developed by researchers at MIT and Stanford University over the last few years, makes it possible to integrate data from prior experiments, and information based on personal observations by experienced workers, into the machine learning process.

While most laboratory-scale development of perovskite materials uses a spin-coating technique, that’s not practical for larger-scale manufacturing, so companies and labs around the world have been searching for ways of translating these lab materials into a practical, manufacturable product.

The MIT team looked at a process that they felt had the greatest potential, a method called rapid spray plasma processing (RSPP). The manufacturing process would involve a moving roll-to-roll surface, or series of sheets, on which the precursor solutions for the perovskite compound would be sprayed or ink-jetted as the sheet rolled by. The material would then move on to a curing stage, providing a rapid and continuous output.

Within that process, at least a dozen variables may affect the outcome, some of them more controllable than others. These include the composition of the starting materials, the temperature, the humidity, the speed of the processing path, the distance of the nozzle used to spray the material onto a substrate, and the methods of curing the material. Many of these factors can interact with each other, and if the process is in open air, then humidity, for example, may be uncontrolled. Evaluating all possible combinations of these variables through experimentation is impossible, so machine learning was needed to help guide the experimental process.

But while most machine-learning systems use raw data such as measurements of the electrical and other properties of test samples, they don’t typically incorporate human experience such as qualitative observations made by the experimenters of the visual and other properties of the test samples, or information from other experiments reported by other researchers. So, the team found a way to incorporate such outside information into the machine learning model, using a probability factor based on a mathematical technique called Bayesian Optimization.

The system now allows experimenters to much more rapidly guide their process in order to optimize it for a given set of conditions or required outcomes. The research team is currently focusing on tech transfer to existing perovskite manufacturers.

For more information, contact Abby Abazorius at 617-253-2709; This email address is being protected from spambots. You need JavaScript enabled to view it..