The photo is sourced from rscf.ru
Perovskites are materials that absorb light and emit rays of a specific wavelength; they are used in the manufacturing of solar cells, photosensors and lasers. The key parameter of perovskites is luminescence efficiency, which was until recently considered impossible to change during operation. Scientists from ITMO University, the Physical-Technical Institute of the RAS and Harbin Engineering University have managed to disprove that assumption, showing that perovskite fluorescence efficiency can be controlled.
For that purpose, the authors of the study created a multilayer material, which they named GST, and which consists of a sapphire substrate and silvery-white metalloids: germanium (Ge), antimony (Sb) and tellurium (Te). Following its production, the material was in an amorphous (i.e., disordered) phase, which is characterised by the absence of a molecular lattice; upon being subjected to laser irradiation, it transformed into a crystalline state. Perovskite was then applied to the GST surface, as a result of which its fluorescence efficiency on crystalline GST was 20% higher than that of perovskite on an amorphous substrate.
Moreover, luminescence efficiency can be changed after the sample has been manufactured. To demonstrate this, the authors shone a laser beam on the GST material. As a result, the amorphous GST transformed into a crystalline state, and its luminescence efficiency increased by 20%. The scientists then subjected the crystalline GST to a single laser pulse, after which the lattice structure of the material resumed a disordered shape. However, the luminescence efficiency dropped by 13% compared to the initial amorphous phase. Finally, at the last stage, the scientists subjected the sample to another series of laser pulses, as a result of which it transformed into a crystalline structure and its fluorescence efficiency again increased by 20% compared to the initial state. Scientists have thus created a perovskite switch.
Tunable light-emitting structures could find a wide range of applications in photonic devices. They could, for instance, be applied on products with fluorescence efficiency adjusted for counterfeit protection.
“Our platform allows us to use materials with phase memory to control the bright luminescence of perovskites. At this stage, we have demonstrated that this platform is fundamentally operational. Further on, we plan to use it to control the directivity and polarisation of luminescence, as well as use the changes in the electrical properties of materials with phase memory to demonstrate the new capabilities of platform-based micro-optoelectronic components,” Mikhail Rybin, doctor of physical and mathematical sciences, senior researcher at the Department of Physics of ITMO University, is quoted as saying by the Russian Science Foundation.