ИСТИНА

Semiconductor quantum dots - particles with 3D restriction of the carrier movement – are subject of vaious studies since they open up possibilities to produce novel materials. The idea to form QD-based nanocomposite media for laser generation is of extreme attraction. In particular, this can be done with the help of II-VI QD (i.e. CdSe) and polymer. Employment of liquid-crystal polymers (LCP) is very promising since they allow formation of ordered QD arrays and high QD concentration. Measurement of QD-LCP nanocomposite photoluminescence (PL) spectra and PL kinetics is the first stage of study of such nanocoposites. It would be also very instructive to compare results obtained both for LCP and amorphous polymer matrices. In this paper, we employed dried CdSe QD sol and nanocomposite based on smectic BA-6PA and amorphous PMBA-6A polymers with various CdSe QD mass fractions (up to 30%). QD diameter was 4.1 nm. PL measurement were carried out under excitation by picosend pulses of 532 nm. PL spectra were registered with the help of Princeton Instrument Acton 2500i spectrometer equipped by gated CCD camera. PL and PL excitation spectra were also obtained by Perkin Elmer LS 55 spectrometer. PL spectra contain two bands (2.15 and 1.70 eV) recombination and radiative recombination in defects (traps) at QD-matrix interface. The latter band intensity increases in LCP matrix in comparison with QD sol and amorphous matrix. The most effective excitation is at 370 nm. In LCP matrix exciton band prevails for QDs with 30 mass. % concentration, whereas for less concentrations defect band PL is more intensive. The exciton PL band is characterized by less PL lifetime than defect one. Increase of QD concentration results in PL lifetime decrease. If amorphous polymer matrix is used, PL signal decreases almost twice in comparison with LCP nanocomposite with the same QD mass concentration. In conclusion, measurements of the excitation and emission spectra of PL of CdSe quantum-size nanoparticles embedded in the polymer matrices, as well as the kinetics of their PL, indicate that the use of a LCP as a matrix makes it possible to increase the lifetime of PL and the quantum yield of this process. This work was supported by Russian Foundation for Basic Research (grant 18-02-00548), synthesis of QDs and polymer matrices was carried out in framework of the State Assignment for IPS (АААА-А18-118011990207-1).