By Joe Rojas-Burke

Discovering cleaner, more efficient energy
Sustainability is a core value in the University of Utah’s Strategic Plan and Campus Master Plan, and developing cleaner, more efficient energy sources will be pivotal. Here’s a roundup of recent energy research advances at the U:

Uncovering the secrets of hybrid perovskite solar cells
The best hope for cheap, super-efficient solar power is a remarkable family of crystalline materials called hybrid perovskites. In just five years of development, hybrid perovskite solar cells have attained power conversion efficiencies that took decades to achieve with the top-performing conventional materials. But what makes the devices so efficient has remained unclear. U scientists, in collaboration with the University of Texas at Dallas, have uncovered some of the secrets behind the amazing material’s performance. Among the practical results of the new study, published in the journal Nature Physics, is proof of a way to rapidly test the performance of different prototypes of hybrid perovskite materials using magnetic fields, according to lead author Charlie Zhang, a postdoctoral research fellow, and senior author Z. Valy Vardeny, a distinguished professor of physics at the University of Utah. The new findings provide more detailed understanding of the underlying physics that should help researchers to fully optimize hybrid perovskite solar cells.

Boosting Solar Cell Efficiency
High-efficiency solar cells are prohibitively expensive to manufacture for large-scale use. But electrical engineers at the U have designed a potentially inexpensive way to boost the overall efficiency of solar cells using a thin layer of a transparent plastic or glass that sorts and concentrates sunlight. Rajesh Menon, a Utah Science Technology and Research assistant professor of electrical and computer engineering at the U calls the optical layer a polychromat. It separates incoming sunlight into distinct spectral bands and concentrates these bands onto different photovoltaic cells, thus optimizing the amount of light that is absorbed and converted into electricity. So far, the team has reported measured increases in output power of around 35.5 percent. Computer simulations show theoretical efficiency gains of greater than 50 percent.

Cheaper, less toxic photovoltaic materials
Many photovoltaic solar cells and semiconductors rely on the highly toxic elements cadmium and arsenic, or require rare and expensive elements such as indium and gallium. U metallurgists have found a way to use a conventional microwave oven to produce a nanocrystal semiconductor using affordable, abundant and less toxic metals.

Michael Free, a professor of metallurgical engineering, and Prashant Sarswat, a research associate in metallurgical engineering, used the method to build a small photovoltaic solar cell to confirm that the material works and demonstrate that smaller nanocrystals display quantum confinement, a property that makes them versatile for different uses.

Hydrogen fuel from sunlight
Hydrogen is the most common element in the universe and it is an emissions-free alternative to power fuel cells. But collecting it requires large amounts of energy or using fossil fuel as a feedstock. Physicist Jordan Gerton and chemist Michael Bartl, both associate professors at the U, are seeking a practical way to make hydrogen fuel from water using sunlight. With collaborators at the Lawrence-Berkeley National Laboratory, the researchers landed a $250,000 grant from Research Corporation for Science Advancement, a foundation is dedicated to funding the high-risk and potentially high-reward investigations of early career scientists. The goal is to fabricate nanowires made of gallium nitride that are highly efficient at gathering energy from sunlight and using it to drive a chemical reaction that splits water molecules into hydrogen and oxygen gas.

Low-emissions coal power
Coal is giving way to cleaner energy sources in the U.S., but not globally. India, for example, plans to double coal production by 2020 to supply its rapidly growing demand for electricity. U researchers are part of an urgent effort to develop low-emissions coal power plants. A $16 million from the U.S. Department of Energy’s National Nuclear Security Administration is enabling U engineering researchers Philip J. Smith and Martin Berzins, along with university President David W. Pershing, to establish the Carbon Capture Multidisciplinary Simulation Center. The researchers are developing advanced computer simulations to predict performance for a proposed next-generation power plant that burns pulverized coal with pure oxygen and captures carbon dioxide from combustion. They hope their findings will expedite deployment of clean, economical power to developing nations, where nearly 1.2 billion people lack electricity, and help industrialized nations meet increasingly stringent emissions standards, like those recently proposed by the Environmental Protection Agency.

Joe Rojas-Burke is a senior science writer at University Marketing and Communications. If you have an interesting story idea, email him at joe.rojas@utah.edu.