Title: Self assembly of CdSe/ZnS quantum dots for organic/inorganic light emitting devices for the next generation display technology

Authors: A. Uddin, C.C. Teo

Addresses: Department of Electrical and Computer Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia. ' School of Materials Science and Engineering, Nanyang Technological University, 639798, Singapore

Abstract: We have investigated the effect of quantum dot (QD) concentrations, spin speed and temperature on the self assembly of CdSe/ZnS QDs on substrate for the optimisation of QDs used in organic light-emitting devices (OLEDs) applications. The atomic force microscopy (AFM) results showed that surface morphology and coverage are varied with different process parameters. There is also a tendency for the formation of aggregates/islands on a smooth substrate that could be caused by spinodal phase separation. The uniform distribution of QDs with controllable density was achieved using the conventional spin-coating method. We fabricated and investigated the effect of CdSe/ZnS QD concentrations on the self-assembly hybrid organic/inorganic light emitting diodes (QD-OLEDs) for the tuning of performance. There was a QD threshold concentration below which there was no emission from the QDs. The estimated QD concentration was around 9 × 10¹¹ cm⁻² for the best performance of QD-OLED. The annealing of QD-OLED increased the QD emission about three times. No wavelength shift was observed in the electroluminescence spectra from the QD before and after the annealing of QD-OLEDs. The mechanism of this emission improvement is discussed.

Keywords: CdSe quantum dots; cadmium selenide; zinc sulfide; organic light-emitting devices; OLED; LEDs; self assembly; Alq3; tris(8-hydroxyquinolinato)aluminium; nanotechnology; nanomanufacturing.

DOI: 10.1504/IJNM.2009.028105

International Journal of Nanomanufacturing, 2009 Vol.4 No.1/2/3/4, pp.3 - 12

Published online: 07 Sep 2009 *

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