March 18, 2014
A research group at UCLA reports a cheaper method to make perovskite-mimic crystals of methyl ammonium halide and lead halide, for use in thin-film PV devices.
Led by Yang Yang, professor of engineering at the UCLA Henry Samueli School of Engineering and Applied Science, the UCLA team devised a vapor-assisted solution process they claim sidesteps problems that hindered scaling of other techniques.
The team coats a substrate with the inorganic (lead halide) component, then treats it in a steam bath of organic component (methyl ammonium halide) at about 150°C (302°F). The organic material infiltrates the inorganic matter and forms a compact, uniform perovskite film.
In test runs, the technique has produced solar cells with a power conversion rate of more than 12 percent. The team is working to improve that rate and to scale the surface up from postage-stamp cells to commercially viable sizes.
The research was published online on Dec. 20 by the Journal of the American Chemical Society, and in the journal’s Jan. 15 print edition.
Yang said there are still technical challenges to overcome, including the material’s propensity to absorb moisture when not properly encapsulated, which degrades its performance. In addition, the lead used in the perovskite production poses environmental concerns.
Huanping Zhou, a postdoctoral researcher in UCLA’s materials science and engineering department and UCLA’s California NanoSystems Institute (CNSI), and the paper’s corresponding author, said the new technique works efficiently because the organic materials’ melting point is low, and the organic and inorganic components react with each other rapidly. She noted that the process may eventually be adapted to produce transistors, light-emitting diodes and other devices.
Qi Chen, a postdoctoral researcher in UCLA’s materials science and engineering department and CNSI, is the lead author of the research. Other authors include Ziruo Hong and Gang Li, research engineers in UCLA materials science and engineering; postdoctoral researcher Yong-sheng Liu; and graduate students Song Luo, Hsin-Sheng Duan and Hsin-Hua Wang, all of UCLA materials science and engineering and CNSI.
The research was supported by the National Science Foundation, the Air Force Office of Scientific Research and UCLA.