Researchers offer new approach to multiphase structuring of halide perovskite
A new publication is co-authored by KFU with ITMO University, Lund University and University of California, Irvine.
From KFU’s side, contributions were made by the Laboratory of Quantum Photonics and Metamaterials and the Laboratory of Ultrafast Calorimetry. The project is supported by a Russian Science Foundation grant ‘Synthesis and research of a new class of nanocomposite ceramics with degenerate dielectric permittivity for optoplasmonic applications’, headed by Professor Sergey Kharintsev.
Co-author, fourth-year student Elina Battalova explains, “The fundamental goal of semiconductor photonics and optoelectronics is to increase the efficiency of the interaction of light and matter on the micro- and nanoscale. In addition to the dimensional effects, point defects in semiconductor crystals are an important obstacle to this process and can significantly reduce photoluminescence or optical absorption. Defects which cannot be eliminated are an integral part of any crystal. However, by changing the electron structure of the semiconductor, it is possible to achieve that the energy levels of the defects will shift beyond the forbidden slot. In this case, defects can improve the optical properties of semiconductors by acting as an optical nano-antenna. This class of semiconductors includes inorganic halide perovskites, such as CsPbBr3, which have been investigated in our work.”
According to the interviewee, one way to increase the quantum output of luminescence is to create heterostructures containing several crystallographic phases. In such materials, defects play a positive role – they become charge attractors in which radiative recombination enhances.
“The phase composition of CsPbBr3 perovskite at different temperatures was studied using a non-invasive method – ultrafast scanning differential calorimetry. We were able to find a trace of defects on the calorimetric curves of individual CsPbBr3 crystals. This opens up new possibilities of scanning ultra-fast calorimetry to solve the problems of solid state flaw detection,” adds Associate Professor Timur Mukhametzyanov.
Phase structuring of perovskite, according to the scientists, is possible due to the generation of a highly localized temperature gradient.
“For this purpose, we have developed a thermoplasma metasurface that provides a local optical heating when illuminated by laser light. By placing the CsPbBr3 crystal on such a metasurface, the phase composition of the semiconductor can be controlled by changing the intensity of the laser light. At room temperature, CsPbBr3 is located in the g-phase with the lowest symmetry. Local photoheating creates a stationary thermal gradient. Under such conditions, several crystalline phases may occur simultaneously within a single crystal, at whose borders the quantum output of photoluminescence is significantly increased by the resulting and existing defects,” concludes Professor Kharintsev.