Solar cells remain a focal point of scientific investigation because the sun offers the most abundant source of energy on earth. The concern, however, with conventional solar cells made from silicon is their cost. Even with recent improvements, they still require a significant amount of electricity and industrial processing to be manufactured.
In 2009, energy researchers turned their attention to a class of materials called “metal halide perovskites,” or MHPs. They are sprayed on like paint onto solid objects, says Joshua Choi, an assistant professor of chemical engineering at the University of Virginia. As the solution dries, the MHPs crystallize into a thin film that can be used to capture energy in a solar cell.
Within just a few years, MHP solar cells have been crafted whose performance rivals conventional silicon solar cells. This is the fastest recorded improvement in history for any photovoltaic material and it has been verified by the National Renewable Energy Laboratory in Golden, Colorado.
The challenge is that these existing MHP solar cells are no larger than a human fingernail.
“To be really technologically relevant,” Choi said, “we need to be able to scale up this process while maintaining or even improving the efficiency of the solar cell. To do that, we need to understand how this material crystallizes and grows from solution into a thin film.”
Collaborating with scientists from Cornell University’s High Energy Synchrotron Source, which receives funding from the National Science Foundation, Choi and his team monitored in real time the growth of MHP crystals at the atomic level by exposing them to high intensity X-rays.
The scientists will present their findings at the 66th meeting of the American Crystallographic Association, held July 22-26 in Denver, Colorado.
By adding different chemicals to the solution, they were able to control how fast the MHP crystals formed and what direction they grew on a surface. The specific orientation of the MHP crystals on a surface affected how well a solar cell performed, Choi said.
Moreover, this research provides this nascent field with the kinds of insights about MHP crystal formation that scientists will need as they determine how to manufacture the larger MHP solar cells that could reduce the price of solar energy.
But there’s more to MHP solar cells than just their potential to cut costs.
“MHP solar cells can be used in flexible, lightweight materials,” Choi said. The ultimate goal would be to make manufacturing MHP solar cells as easy as printing newspapers, generating rolls of thin solar cell material that could be easily applied to houses, cars, or anywhere else they were needed.
One significant drawback with many current MHP solar cells is that they contain lead. Researchers are working on identifying viable alternative compositions that are not toxic.
Choi and his research are funded by NASA, which is examining the potential for MHPs to be used in high temperature solar cells that could be installed in solar probes deployed in space. Elsewhere, MHPs have already been used in lasers, photo detectors, transistors and light emitting diodes (LEDs).
Still, it is the solar cell that arguably offers MHPs the best chance to address pressing global problems.
“To mitigate the impact of climate change and also to ensure the energy security of the United States and the world, it is very important to come up with renewable energy sources rather than just be relying on fossil fuel-based energy,” Choi said.
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Presentation 04.02.04: “Understanding and controlling the preferential orientation of metal halide perovskite thin films for high performance solar cells” by Joshua Choi, Benjamin Foley, Alexander Chen and Detlef-M. Smilgies will take place on Sunday, July 24, 2016 at 10:50 AM MDT in Governors Square 15. Abstract: https://aca.confex.com/aca/2016/webprogrampreliminary/Paper1157.html
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MORE ABOUT THE MEETING
More than 600 professionals and students from more than 20 countries and from diverse areas across industry and academia are expected to attend the American Crystallographic Association (ACA) 66th annual meeting in Denver, CO, from July 22-26, 2016, the largest crystallography conference of the year in the United States.
All scientific sessions, exhibit shows and poster sessions will be held at the Sheraton Denver Downtown Hotel. To obtain more information or free registration for press, please contact the AIP Media Line at [email protected] or 301-209-3090.
USEFUL LINKS
Main meeting website: http://www.amercrystalassn.org/2016-meeting-homepageScientific program: http://www.amercrystalassn.org/2016-scientific-programHotel: http://www.sheratondenverdowntown.com/Twitter: #ACADenver
ABOUT THE SCIENCE OF CRYSTALLOGRAPHY
Crystallography is a field that lies at the crossroads of biology, chemistry, physics and materials science. Researchers from areas as far flung as genomics, geology, medicine and manufacturing use it to uncover the exact arrangements of atoms within molecules and bulk materials -- information of keen interest to modern science because it helps to define the real-life chemical and physical properties of materials. The structures uncovered by crystallography are also of profound importance to humanity because they are routinely used to guide the creation of new lifesaving drugs, improve manufacturing processes and make new materials that impact our economy and our world. 29 Nobel Prizes have been awarded for work involving crystallography. One of the most important achievements in the field is establishing the structure of DNA.
ABOUT ACA
The American Crystallographic Association (ACA) was founded in 1949 through a merger of the American Society for X-Ray and Electron Diffraction (ASXRED) and the Crystallographic Society of America (CSA). The objective of the ACA is to promote interactions among scientists who study the structure of matter at atomic (or near atomic) resolution. These interactions will advance experimental and computational aspects of crystallography and diffraction. They will also promote the study of the arrangements of atoms and molecules in matter and the nature of the forces that both control and result from them. See: http://www.amercrystalassn.org
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Meeting Link: American Crystallographic Association (ACA) 2016 Annual Meeting
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