Available online at www.HighTechJournal.org HighTech and Innovation Journal Vol. 3, No. 2, June, 2022 140 ISSN: 2723-9535 Ab-initio Study of Structural and Electronic Properties of Perovskite Nanocrystals of the CsSn[Br 1−x I x ] 3 Family D. D. Nematov 1, 2* , Kh. T. Kholmurodov 3 , D. А. Yuldasheva 2 , Kh. R. Rakhmonov 1 , I. T. Khojakhonov 2 1 S.U. Umarov Physical-Technical Institute of the National Academy of Science of Tajikistan, Dushanbe, Tajikistan. 2 Osimi Tajik Technical University, 724000, Dushanbe, Tajikistan. 3 Joint Institute for Nuclear Research, 141980, Dubna, Moscow Oblast, Russia. Received 12 December 2021; Revised 02 February 2022; Accepted 11 February 2022; Available online 19 February 2022 Abstract In this study, by means of quantum-chemical calculations within the framework of density functional theory, we considered a number of structural and electronic properties of nanocrystals of the CsSn[Br1−xIx]3 (systems CsSnBr3, CsSnBr2I, CsSnBrI2 and CsSnI3) and discussed the effect of iodine concentration on the geometry and electronic properties of these materials. The exchange correlation effects of electrons were taken into account by the LDA, GGA and the modified Becke-Jones exchange correlation potential (mBJ). The results obtained in the framework of the DFT- mBJ and the Wien2k packages are in good agreement with the data from experimental measurements and open up the possibility of accurately predicting a number of fundamental properties of perovskite-like complex structures and the development of new materials. Keywords: Band Gap; Density Functional Theory; Electronic Structure; Perovskite; Wien2k Package. 1. Introduction The possibilities of converting solar energy and other unconventional forms of energy into electricity are considered in the context of projected global energy needs for the 21 st century. Therefore, a very urgent task facing scientists and engineers today is the study of a number of electronic, optical, thermal, and other characteristics of new materials with the aim of their application in solar energy. To successfully make the transition from fossil fuels to renewable energies and confront climate change and pollution, we can no longer rely solely on existing materials, but must focus on synthesizing other classes of materials with improved properties. Moreover, the demand for energy is constantly increasing with population growth, and the gap between demand and supply also widens over time. Conventional energy production methods will no longer be able to meet the world's energy needs. Therefore, unconventional measures, including the creation of photovoltaic devices, wind farms, and moisture-to-electricity converters, are of great interest, and for the implementation of these tasks and the transition to Green Energy, countries around the world allocate a huge amount of money and support scientists and engineers to strengthen their research work. The effect of converting light into electricity was discovered back in 1839 by Alexander Edmond Becquerel, after which Charles Frits and Jacamo Luigi made the first attempt to create the first light-to-electricity converter, but * Corresponding author: dilnem@mail.ru http://dx.doi.org/10.28991/HIJ-2022-03-02-03  This is an open access article under the CC-BY license (https://creativecommons.org/licenses/by/4.0/). © Authors retain all copyrights.