Proceedings of September Meeting 2016 (NFM16)
Publication date: 14th June 2016
Air-stable, near-to-mid-infrared emitting solids of PbTe/CdTe core-shell colloidal quantum dots
Tanja Zünd, Loredana Protesescu, Maryna I. Bodnarchuk and Maksym V. Kovalenko
Infrared active devices used in telecommunication, photodetectors, high-resolution gas analysis and medical diagnostics require material with narrow bandgap energies that cover the broad infrared area. In particular, in the region beyond 1 µm wavelength where silicon-based technologies cannot operate, colloidal quantum dots (QD) become a competitive class of materials.
Due to the quantum-size tuning of the bandgap, inexpensive colloidal synthesis, facile solution procession and facile device integration, various lead chalcogenide quantum dots (PbX QDs, X= S, Se, Te) and HgTe were investigated and were shown to exhibit bright photoluminescence (PL) in the near-infrared region. However, entering the mid-infrared region with PbTe and PbSe QDs had remained a challenge due to intense surface oxidation upon even brief exposures to air or by traces of moisture in common solvents. On contrary, PbTe QDs grown by molecular beam epitaxy1 were demonstrated to retain bright mid-infrared emission due to protective effect of the CdTe matrix.
Herein we combine the advantage of protecting the PbTe core in a CdTe shell with a cheap all-solution based process to obtain air stable thin films. The developed procedure2 starts with a formation of a CdTe shell through the cation exchange reaction. The next step is spin coating of thin films, followed by ligand removal and CdCl2-promoted fusion of the CdTe shells. The obtained PbTe/CdTe QD solids exhibit bright and stable near- to mid-infrared emission at wavelengths of 1–3 µm, which is also retained upon prolonged storage at ambient conditions for at least one year.
1 W. Heiss, H. Groiss, E. Kaufmann, G. Hesser, M. Bçberl, G. Springholz,F. Schäffler, K. Koike, H. Harada, M. Yano, Appl. Phys. Lett., 2006, 88, 192109
2 L. Protesescu, T. Zünd, M.I. Bodnarchuk, M.V. Kovalenko, ChemPhysChem, 2016, 17, 670-674
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