Synthesis of cadmium selenide quantum dots for fabrication of hybrid light emitting diodes.

Abstract

McCreary, Michael 1991-, "Synthesis of cadmium selenide quantum dots for fabrication of hybrid light emitting diodes." (2014 ABSTRACTThe 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 vii 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.viii

Recent Developments in Applications of Quantum-Dot Based Light-Emitting Diodes

“…Though OLEDs have the guarantee to overcome the traditional LEDs in performance, OLED materials and manufactural processes of them are not sufficiently advanced to offer this economically [75]. By the evolving a hybrid tool, the efficiency can be increased and the manufactural price can potentially be reduced because this hybrid material system is compatible with inexpensive fabrication procedure such as solution processing and rollto-roll deposition and with patterning methods, enabling multicolor light sources to be prepared on the same substrate by replacing the emissive colloidal QD coating [14,75].…”

“…The motivation why this design was chosen is to be able to inkjet print the entire tool, at least the polymer and QD layers [75]. The researcher proposed a structure of the hybrid device which is of type ITO/PEDOT/CdSe QD/Au and is shown in Figure 1(A) [75].…”

“…[75]. (B) An energy bandgap scheme of the proposed QD-LED and the suggested materials that were used to construct this type of QD-LED [75].…”

“…Also, the same author explained the manufacture of a hybrid LED with the structure ITO/ PEDOT: PSS/PVK/CdSe QD/Alq3/Al [75]. In order to ease proper hole transport and adequate QD coating, the researcher used a PVK/QD composite solution to make a monolayer layer of QDs using phase separation of the solutes in solution.…”

“…This physical modeling of hybrid QD-LEDs of this type, such as those mentioned before [75], makes them applicable to a diversity of hybrid organic QD optoelectronics tools like LEDs, solar cells, photodetectors, and chemical sensors.…”