QUANTUM CHEMICAL SIMULATION OF CdS/CdSe "CORE/SHELL" QUANTUM DOTS FOR SOLAR CELLS
Quantum dots are promising materials for creation of new generation photovoltaic cells with wide application due to their specific photophysical behavior, narrow emission bands, adjustable band gaps, significant extinction coefficients, and good stability in water and in air. In addition, the use of quantum dots allows you to significantly improve the efficiency of solar energy converters due to the effect of multiple exciton generation with single-photon absorption. However, the difficulty in obtaining uniform coating of quantum dots, surface defects, high probability of charge recombination and a number of other related processes significantly reduce the effectiveness of such photovoltaic cells. Cadmium selenide has high absorption coefficients and good stability. The band gaps of nanostructures and films of cadmium sulfoselenide can be varied with the molar fraction of sulfur in the alloy in the range that covers the entire visible spectrum. Therefore, cadmium sulfide and selenide-based materials have found application in nanolasers, optical devices, photoluminescence devices with color tuning, and in tunable magneto-optical radiation. The application of such materials requires an explanation of the observed effects and the development of methods for directed modification of their properties. Theoretical methods of quantum chemistry can be used for the systematic study of semiconductor quantum structures for prediction of their physicochemical behavior and for the directional simulation of devices of various applications with given characteristics. In this work, we simulated the structural and electronic properties of cadmium sulfide quantum dots coated with cadmium selenide, using the density functional theory method. We have calculated the band gap, analyzed the influence of the shell on geometric characteristics and properties of a quantum dot and studied the deviation of the surface morphology from the internal structure of a particle. Electron dispersion was calculated for the studied quantum dots in solar cells.