Discovery highlights the synthesis and treatment of high-performance solar cells

Perovskite halide solar cells are promising for the next generation of solar cell technologies, but researchers have developed techniques to improve the characteristics of their materials, but no one understood why these techniques worked. New research sheds light on the scientific underpinnings of these engineering solutions and paves the way for the development of more efficient halide perovskite solar cells.

"This is the design of materials," says Aram Amassian, co-author of an article on the book and associate professor of materials science and engineering at North Carolina State University.

"If you deliberately want to design perovskite halide solar cells that have the desirable characteristics you're looking for, you need to understand not only how the material behaves in different conditions, but also why," says Amassian. "This work gives us a more complete understanding of this class of materials, and this understanding will inform our work to move forward."

Perovskites in the form of halides are essentially salts, the positively and negatively charged components of which combine to form a neutral compound. And they have several features that make them desirable for making high efficiency solar cells. They can be dissolved in a liquid and then form crystals of high quality at low temperatures, which is interesting from the point of view of manufacture. In addition, they are easy to repair and can tolerate defects in the material without their semiconductor properties deteriorating.

An international team of researchers has explored a key phenomenon related to the synthesis and treatment of halide perovskite-based solar cells. This implies that the addition of cesium and rubidium in the process of synthesis of mixed halide perovskite compounds makes the resulting solar cell more homogenous chemically, which is desirable, as far as the characteristics of the material are more uniform throughout the cell. But until now, no one knew why.

To investigate the problem, researchers used time-resolved, color-coded X-ray diagnostics to capture and track changes in crystalline compounds formed during the synthesis process. Measurements were made at the Cornell High Energy Synchrotron Source.

"These studies are essential to define the next steps towards the commercialization of perovskite-based solar cells," says Stefaan De Wolf, co-article correspondent and associate professor in Materials Science and Engineering at the University of California. King Abdullah University of Science. and technology (KAUST).

"What we have found is that some of the precursors, or ingredients, want to form several compounds other than the one we want, which can group key elements in an irregular way in the material," Amassian says. "It was something we did not know before.

"We also found that the simultaneous introduction of cesium and rubidium in the process effectively suppresses the formation of these other compounds, thus facilitating the formation of the perovskite compound to the homogeneous and desired halide used for manufacturing high performance solar cells. "

Next steps in the work include translating these lessons from laboratory centrifuge coating into large-scale manufacturing platforms, which will enable the high-speed fabrication of perovskite solar cells.