Tunable blue-shift of the charge-transfer photoluminescence in tetrapod-shaped CdTe/CdSe nanocrystals

The photoluminescence peculiarities and the excited state absorption of the tetrapod-shaped CdTe/CdSe nanocrystals are studied in the single-photon excitation regime. A giant blue shift (≈ 129 meV) of the charge-transfer photoluminescence spectra is revealed for the first time in the molecular nanoscale donor–acceptor system with the pump intensity growth. The photoluminescence lines of the CdTe and CdSe domains, originating from direct electron-hole transitions were observed in addition to the tunable photoluminescence across the indirect gap. Differential transmission spectra reveal the superposition of the exciton's transitions bleaching originating from different structural domains of the CdTe/CdSe nanocrystals, which confirms the observed separated excitonic emission bands in the photoluminescence spectra. The observed features of the photoluminescence and differential transmission spectra allow to determine and to analyze possible exciton's relaxation channels in the CdTe/CdSe nanocrystals. Obtained results make nanocrystals in the form of nano-tetrapods promising for implementation in optoelectronic nanodevices.