Photoluminescence properties of CdTe/CdTeSe/CdSe core/alloyed/shell type-II quantum dots

We report investigations on the crystal structure and optical properties of CdTe/CdTe0.5Se0.5/CdSe (CdTe/CdTeSe/CdSe) core/alloyed/shell (C/A/S) type-II structure and comparison with CdTe core and CdTe/CdSecore/shell (C/S) quantum dots. The analysis of crystal structure by X-ray diffraction and phonon vibration approve for a composition-tuned of C/A/S structure. Tuning C/S composition and structure, we are able to confine holes in the core, and delocalize electrons both in the shell and alloyed. The photoluminescence (PL) arises from a tunneling of electrons through the alloyed layer at low pump fluence. At higher excitation power, the PL reveals a large blue-shift (46 meV) and a peak broadening toward to high-energy, which can be explained by the second recombination route of electrons and holes in the alloyed and core, respectively. An important implication of these results is the possibility of tunable dual emission by laser power, and approves for the tunneling exciton recombination. (C) 2019 Elsevier B.V. All rights reserved.