Photoluminescence of CdSe and CdSe/ZnS Quantum Dots in Amorphous and Liquid-Crystalline Polymer Matrices

The influence of the structure of the polymer matrix on the main photoluminescence characteristics of composites based on core (CdSe) and core–shell type (CdSe/ZnS) quantum dots embedded in liquid-crystalline and amorphous polymers of similar chemical structure is studied. The photoluminescence spectra consist of two bands (2.15 and 1.70 eV), the first of which corresponds to the radiative recombination of excitons, and the second one corresponds to carriers captured by traps at the quantum dot boundary. The second band is absent in the case of CdSe/ZnS quantum dots embedded in the liquid-crystalline polymer matrix. The kinetics of photoluminescence is well described by the sum of two decaying exponentials for CdSe quantum dots in matrices of both types and CdSe/ZnS quantum dots in the amorphous matrix. To determine the photoluminescence kinetics in the case of CdSe/ZnS quantum dots in the liquid-crystalline matrix, one exponential is sufficient. These effects are explained by the appearance of regions with closely spaced quantum dots, in which, in particular, the resonance transmission of excitation is possible.