Tunable dual emission in type-I/type-II CdSe/CdS/ZnSe nanocrystals

N. X. Ca, N. T. Hien, P. M. Tan, T. L. Phan, L. D. Thanh, P. V. Do, N. Q. Bau, V. T.K. Lien, H. T. Van

Research output: Contribution to journalArticle

Abstract

We have used wet chemical methods to fabricate colloidal CdSe/CdSm/ZnSen core/intermediate/shell (C/I/S) nanocrystals (NCs), where m = 1 and 2 and n = 1–4 are the number of monolayers. The growth was monitored by using Raman and UV–vis spectroscopy, which demonstrated the formation of correct CdSe/CdSm/ZnSen C/I/S NCs. X-ray diffraction studies proved single-phase NCs crystallized in the zincblende-type structure. Photoluminescence (PL) studies have indicated that after photoexcitation C/I/S NCs generate simultaneously type-I and type-II emissions, namely E I and E II , associated with CdSe/CdSm and CdSm/ZnSen structures, respectively. For a specific value of m = 2, we have found the redshift of both E I and E II emissions when n is increased from 1 to 4. The PL studies versus the laser-excitation power (P ex ) up to about four orders of magnitude allow us to identify the origin of two emissions. A large blueshift of the E II peak is ascribed to the band bending effect resulting from the spatially separated photoexcited carriers in type-II NCs. It appears that the dependence of the E II peak on the cube root of P ex (P ex 1/3 ) is linear while that of the E I peak on P ex 1/3 is almost constant. In this work, we also point out that the emission intensity (I) of E I and E II can be tuned by changing the values of n and P ex , where I obeys a power law I∝P ex k , with k = 0.7–1.0 dependent on the emission type. The nature of these phenomena is discussed in comparison with previous studies on C/S and C/I/S nanoheterostructures.

Original languageEnglish
Pages (from-to)144-151
Number of pages8
JournalJournal of Alloys and Compounds
Volume791
DOIs
Publication statusPublished - 30 Jun 2019

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    Ca, N. X., Hien, N. T., Tan, P. M., Phan, T. L., Thanh, L. D., Do, P. V., Bau, N. Q., Lien, V. T. K., & Van, H. T. (2019). Tunable dual emission in type-I/type-II CdSe/CdS/ZnSe nanocrystals. Journal of Alloys and Compounds, 791, 144-151. https://doi.org/10.1016/j.jallcom.2019.03.333