Researchers Deploy New Process For Lighter, More Efficient Solar Power Technology
Imagine a TV set so thin it could be rolled up like a newspaper, or a thin film that could cover an entire building and generate solar power. Perovskites could make this possible.
Perovskite is a type of mineral, but the word can also refer to a range of laboratory-made materials that share the same unique crystal structure and exhibit properties such as photoconductivity and the ability to be made into inks. This latter property is what makes it possible to print perovskites on flexible pieces of plastic – the same way newspapers are printed. It could someday make it possible to print very efficient, ultra-thin solar cells, or something like a TV or LED light thin enough to roll up.
“For me, the potential flexibility and light weight of perovskites provide key competitive advantages in applications such as portable devices, avionics and disaster relief power where size and portability are critical constraints.” said Adam Printz, assistant professor of chemical and environmental engineering at the University of Arizona. âPerhaps most exciting is that these benefits come without any significant compromise in the performance of the device.â
The reason why perovskites are not even more widely used is that, as a relatively new technology, they are still very unstable. To overcome the instability, Printz has developed a new printing process called Ink Drawing Restricted Area Printing, or RAPID. He received a three-year grant of $ 700,000 from the Department of Energy Solar Energy Technologies Office (SETO) to advance the method.
Printz has been selected under the SETO FY20 perovskite funding program, which aims to rapidly scale up affordable solar deployment, meet the country’s clean energy goals, and create well-paying jobs in the states. -United. Its co-researchers are Erin Ratcliff, associate professor of chemical and environmental engineering at the UArizona; and Neal Armstrong, UArizona Regents Professor Emeritus in Chemistry, Biochemistry, and Optical Sciences.
âThis effort is an exciting opportunity for the Arizona College of Engineering and the College of Engineering to lead in the processing of printable solar materials, a key strategic area for the Institute for Energy Solutions and the Arizona Institutes for Resilience,â said Ratcliff . “Metal halide perovskites are a very hot technology, and there is a lot of interest and enthusiasm in the industry. It will be a great educational opportunity for our students for years to come.”
Solar energy and the spaces between
Solar energy is one of the areas where perovskites have the greatest potential. Since the 1950s, most solar cells have been made of silicon wafers, which convert light into electricity. Standard industrial silicon solar cells typically do this with an efficiency of around 18-22%. Perovskites are a much newer technology, but their effectiveness is increasing at an unprecedented rate – from around 3% in 2006 to 25% today. Perovskite solar cells are also cheaper to produce than their silicon counterparts because they require much less material and production time.
Printz and his team started developing their perovskite printing process in late 2019, and they were able to demonstrate on a small scale with 3D printed parts how it works – using “everything they had in the lab”. This funding allows them to create a more reproducible and scalable version.
Perovskite materials are made by spreading a thin layer of specialized ink on a surface and then heating the ink to cause the crystal structure of perovskite to form. This printed film consists of many tiny grains separated by boundary areas. Under a high powered microscope, it looks like dry, cracked mud. It is in these boundary zones – which are more chemically reactive than the grains themselves – that things can get complicated.
âThese boundary zones can actually interact with moisture in the air and turn perovskite into a completely different material that doesn’t absorb light – making it a terrible solar cell,â Printz said. “We want to minimize the surface area of ââthe grain boundaries so that these reactions don’t occur, and the perovskite is more likely to remain perovskite.”
Thus, the aim of RAPID is to produce as few border areas as possible. To do this, it uses a confined printing area so that large grains can be formed without the solvent evaporating too quickly under the effect of heat. Larger grains mean a reduced boundary area between grains, and a reduced boundary area equates to more stability and efficiency.
During this three-year project, Printz and his team aim to reduce grain boundaries by 90%. They also hope to improve the efficiency stability of perovskite solar cells by 50%, or their ability to maintain their efficiency over time.
âWhen RAPID goes into large-scale operation, we hope it will have profound impacts on the production of perovskites, greatly improving the stability of these low-cost, high-efficiency devices,â said Printz.
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