Perovskites are materials composed of organic compounds attached to a metal. Due to their structure and properties, driven at the forefront of materials research, perovskites are focused on a wide range of applications, including solar cells, LED lights, lasers, and photodetectors.
This latest application, photo or light detection, is of particular interest to scientists at EPFL’s School of Basic Sciences, who have developed perovskite that can detect gamma rays. Researchers have published their work under the guidance of the laboratories of professors Lászlo Forró and Andreas Pautz Advanced Science.
“This perovskitic photovoltaic crystal grown at this kilogram size is a game changer,” says Forro. “You can split silicon into sheets for optoelectronic applications, and in this paper we show its usefulness in gamma ray detection.”
Gamma ray control
Gamma rays are the penetrating electromagnetic radiation generated by the radioactive decay of atomic nuclei, for example, in nuclear explosions or even in supernovae. Gamma rays are located at the shortest end of the electromagnetic spectrum, which has the highest frequency and highest energy. Therefore, they can contain almost any material, and are widely used in homeland security, astronomy, industry, nuclear power plants, environmental control, research, and even medicine to detect and control tumors and osteoporosis.
But specifically, since gamma rays can affect biological tissue, we need to keep an eye on them. To do this, we need simple, reliable and inexpensive gamma ray detectors. The perovskite developed by EPFL scientists is based on methylammonium lead tribromide crystals (MAPbBr3) and appears to be the perfect candidate that meets all of these requirements.
Perovskites “grow” like crystals as before, and the quality and clarity of the crystals determine the effectiveness of the material when it becomes a thin film that can be used on devices such as solar panels.
The perovskite crystals made by EPFL scientists show great clarity with very little impurities. When they tested gamma rays on crystals, they found that they were producing photographic carriers with a high “product for all mobility,” which is a measure of the quality of radiation detectors. In summary, perovskites can effectively detect gamma rays at room temperature by measuring their resistivity.
Cheaper and scalable synthesis
It is part of the MAPbBr3 family of Perovskite “metal halides”, which, unlike the leading crystals on the market, can be grown from a variety of raw materials and at low cost. The synthesis takes place in solutions close to room temperature, without the need for expensive equipment.
Of course, this is not perovskite made for the detection of gamma rays. But the volume of most metal halide perovskites in the laboratory used for this is about 1.2 ml, which is hardly scalable to commercial levels. However, the EPFL team also developed a special method called “oriented crystal-to-crystal growth” that allowed them to make a whole liter of glass weighing 3.8 kg.
“Personally, I really enjoyed working within the normal limits of condensed matter physics, chemistry, and reactor physics, and seeing that this collaboration could lead to important application in our society,” says lead author Pavao Andričevic.
Reference: Pavao Andričević, Pavel Frajtag, Vincent Pierre Lamirand, Andreas Pautz, Márton Kollár, Bálint Náfrádi, Andrzej Sienkiewicz, Tonko Garma, Lászl 9 December 2020 Advanced Science.
DOI: 10.1002 / advs.202001882