New discoveries made concerning a promising solar cell material, thanks to new microscope

• A team of scientists from the Department of Energy's Ames National Laboratory has established a new characterization device that allowed them to gain unique insight right into a feasible different material for solar cells.

Under the management of Jigang Wang, senior scientist from Ames Lab, the team established a microscope that utilizes terahertz waves to collect data on material samples. The team then utilized their microscope to discover methylammonium lead iodide (MAPbI3) perovskite, a material that can possibly replace silicon in solar cells.

Richard Kim, a scientist from Ames Lab, clarified the two features that make the new scanning probe microscope unique. First, the microscope uses the terahertz series of electromagnetic frequencies to collect data on materials. This array is far listed below the visible light spectrum, dropping between the infrared as well as microwave frequencies. Secondly, the terahertz light is beamed via a sharp metal suggestion that boosts the microscope's capabilities toward nanometer length scales.

" Usually if you have a light wave, you can not see things smaller than the wavelength of the light you're using. As well as for this terahertz light, the wavelength has to do with a millimeter, so it's quite large," described Kim. "However here we utilized this sharp metallic idea with a pinnacle that is developed to a 20-nanometer radius curvature, and this functions as our antenna to see things smaller than the wavelength that we were making use of."

Using this new microscope, the team investigated a perovskite material, MAPbI3, that has actually lately become of passion to researchers as an option to silicon in solar cells. Perovskites are a special sort of semiconductor that transfers an electric charge when it is subjected to visible light. The primary challenge to making use of MAPbI3 in solar cells is that it deteriorates easily when exposed to components like warmth and also wetness.

According to Wang as well as Kim, the team anticipated MAPbI3 to act like an insulator when they subjected it to the terahertz light. Because the data collected on a sample is an analysis of exactly how the light scatters when the material is exposed to the terahertz waves, they expected a regular low-level of light-scatter throughout the material. What they discovered, nevertheless, was that there was a lot of variation in light scattering along the limit between the grains.

Kim explained that conductive materials, like metals, would certainly have a high level of light scattering, while less conductive materials like insulators would not have as much. The wide variation of light scattering identified along the grain boundaries in MAPbI3 clarifies the material's degradation issue.

Throughout a week, the team continued to collect data on the material, and also data collected in that time showed the degradation process via changes in the degrees of light spreadings. This info can be useful for improving and also adjusting the material in the future.

" Our team believe that the here and now research demonstrates a powerful microscopy device to visualize, comprehend and possibly mitigate grain border degradation, issue traps, and also materials deterioration," stated Wang. "Better understanding of these concerns may enable establishing extremely efficient perovskite-based solar tools for years ahead."

The samples of MAPbI3 were offered by the University of Toledo. This study is further gone over in the paper "Terahertz Nanoimaging of Perovskite Solar Cell Materials," composed by Richard H. J. Kim, Zhaoyu Liu, Chuankun Huang, Joong-Mok Park, Samuel J. Haeuser, Zhaoning Song, Yanfa Yan, Yongxin Yao, Liang Luo, and Jigang Wang, as well as published in the ACS Photonics.