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Quantum dots of the group of wide-gap and narrow-gap semiconductors are synthesized and investigated under identical conditions, which makes it possible to perform the comparative analysis and modeling of the mechanisms of radiative recombination and luminescence, for which a stable exciton bond between the electron and hole has an important role. Exciton states are unstable for quantum dots without a shell and narrow-gap semiconductors, which leads to a substantial decrease in the probability of radiative recombination and, correspondingly, the quantum yield of luminescence. The experimental values of the spectral position of the luminescence maximum for quantum dots with clear manifestation of the exciton recombination mechanism noticeably shift to the long-wavelength region with respect to the calculated ones. In calculations and analysis, we use the effective electron mass for bulk semiconductors. The observed good correspondence of the calculated values of the maximum and spectral band with the experiment can mean that quantum dots have a long-range order crystalline structure similar to that one observed in single crystals and polycrystals.

Direct methods (using a laser particle size analyzer) and indirect (from the analysis of spectral characteristics and differential normalized tunnel CVC) methods of CdSe QD size estimation allowed determination of the size (4-5 nm) and shown good qualitative and quantitative agreement of the results with an error of less than 10 %. It is concluded that the tunnel differential CVC analysis is an effective method for express measurement that can be used in quantum-size object investigations.

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