Colour Centre IGIС RAS

Perovskites are a class of materials with the general formula ABX3; among the compounds having the structure of perovskite, oxides, halides, and intermetallides are distinguished. The structure of perovskite (or its derivative) is possessed by high-temperature superconductors, ionic conductors, as well as many magnetic and ferroelectric materials. In the last few years, hybrid (organo-inorganic) perovskites based on lead halides have been of particular interest as functional materials in photovoltaic devices such as perovskite solar cells, LEDs, photodetectors, lasers, etc., due to their unique optical and electronic properties such as high absorption coefficient, low exciton binding energy, the ability to band gap settings, high mobility of charge carriers, as well as high resistance to defects. Perovskite structures are also successfully used as X-ray sensors. Modern high–quality optoelectronic devices, in particular LEDs, are made on the basis of semiconductors with a direct band gap such as gallium arsenide, zinc selenide, etc., however, the manufacture of such devices is not an easy task, since the process of their creation is laborious, expensive and energy-consuming. Perovskite nanocrystals based on lead and caesium halides can become a real alternative to the semiconductors used. CsPbX3 perovskite nanoparticles have such properties as a wide absorption spectrum and a bright photoluminescence band in the visible spectral region, a large diffusion path length of photoexcited charge carriers, as well as the ability to adjust the emission band by changing the composition and size of nanoparticles. The main method of obtaining perovskite nanoparticles is colloidal synthesis, the advantages of which are the prostate of obtaining the material and low cost.

An important task of the Center is to create photosensitizers based on transition metal complexes for photovoltaics. Promising are organometallic compounds of iridium(III) and ruthenium(II), which are able to effectively capture solar radiation and participate in its conversion into electric current, that is, work in solar panels. The Center's staff developed and synthesized organic antenna molecules based on imidazole, whose derivatives are widely distributed in wildlife, the addition of which to ruthenium or iridium repeatedly enhanced the light absorption of the resulting organometallic compounds compared with individual components. Iridium compounds with panchromatic absorption (up to 1000 nm) have been obtained. Iridium complexes with organic ligades having an extended conjugate system have been obtained. The compounds exhibit intense light absorption up to 550 nm with molar absorption coefficients of the order of 10,000 l/mol/cm. Photosensitizers were developed and synthesized, in which the localization of the excited state was controlled, which led to an increase in the efficiency of converting sunlight into electricity.

Within the framework of the electrochromic nanomaterials direction, the following tasks are being solved: the development of modern approaches to the synthesis of oxide nanomaterials (primarily based on vanadium and tungsten oxides), the production of stable dispersed systems based on appropriate nanoparticles, the formation of oxide films using the obtained dispersed systems and printing technologies, as well as the determination of electrochromic characteristics of the created planar nanostructures for evaluation of the possibility of their use as components of "smart" windows. Thus, the team studied the processes of liquid-phase synthesis of a number of nanomaterials based on tungsten and vanadium oxides, differing in size and shape of particles, which were successfully used in the manufacture of prototypes of electrochromic devices (Fig. 1). At the same time, for the application of a functional oxide layer, which is an array of miniature planar WO3 nanostructures with a dimeter of about 150 microns, microplotter printing is used, which allows targeted application of the required dose of ink to a given area of the modified glass substrate. The team's work is aimed at expanding the range of materials that are promising as active components of smart windows, as well as increasing their efficiency in terms of optical contrast and energy consumption of the electrochromic devices being created.