Date on Master's Thesis/Doctoral Dissertation

4-2014

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Chemical Engineering

Committee Chair

Amos, Delaina A.

Author's Keywords

Quantum dots; LED; CdSe

Subject

Light emitting diodes; Quantum dots; Cadmium selenide

Abstract

The synthesis of CdSe quantum dots was carried out using a variety of methods including co-precipitation method, reverse micellar method, and hot injection method. Of these three methods, only the hot injection method produced an immediately viable product for application in the hybrid light emitting diode proposed. The co-precipitation method did generate the ability to perform the reverse micellar method which produced ~30 nm diameter nanorods of mostly amorphous material. These rods were analyzed using XRD, and TEM. The hot injection method using octadecene as the solvent and various ligands, including oleic acid, benzene-1,4-dithiol, mercapto-benzoic acid and TOP, created quantum dots exhibiting photoluminescence in the green region of the visible spectrum. These quantum dots were characterized using UV-Visible Spectroscopy and Photoluminescence Spectroscopy. The oleic acid capped QD had a characteristic wavelength of 560 nm. While the mercapto-benzoic acid and benzene-1,4-dithiol capped QD had a characteristic wavelengths of 510 nm and 555 nm, respectively, all under the same operating conditions. For the purposes of device fabrication, the NN-Labs QDs were mostly used because their performance was much better than quantum dots synthesized in house. The fabrication of a hybrid light emitting diode has been developed with the structure ITO/PEDOT:PSS/PVK/CdSe QD/Alq3/Al. The device has exhibited a turn-on voltage from 2-3 V with currents ranging from 4-5 mA. The PEDOT:PSS layer was deposited using spin coating and analyzed using Photoluminescence Spectroscopy, Atomic Force Microscopy, Optical Microscopy, and Surface Profiling. The layer produce is sufficient for device fabrication. To facilitate proper hole transport and a sufficient quantum dot layer, a PVK/QD composite solution was used to create a monolayer layer of quantum dots by phase separation of the solutes in the solution. Alq3 and Al were deposited using thermal evaporation techniques.

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