Font Size: a A A

Study Of Quantum Dots Light-emitting Diodes And Carriers Control

Posted on:2019-04-09Degree:MasterType:Thesis
Country:ChinaCandidate:Z W HeFull Text:PDF
GTID:2428330566486187Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
Quantum dots(QDs)have been widely used in quantum dots light emitting diodes(QLEDs),due to their unique optical properties such as size-dependent emission wavelength,sharp emission peak,and high luminescent quantum efficiency.It's widely regarded as a great candidate for next-generation flat panel display technology.White quantum dots light-emitting diode(WQLEDs)has gradually attracted much attention.The white light devices based on quantum dot electroluminescence can be divided into full quantum dot white light and organic/quantum dot hybrid white light according to the composition of the light emitting layer.Because organic blue has higher efficiency and longer lifetime than blue quantum dots,organic blue/quantum dots hybrids may be a more effective way to prepare WQLEDs.Based on the injection and transmission of electrons,high efficiency organic/quantum dot hybrid white light were prepared by the normal and inverted devices,respectively.In the normal devices,by comparing the electroluminescent spectra of the devices with Ba/Al and ZnO/Al as the cathode respectively,it is found that Ba/Al cathode quenches the luminescence of QDs seriously;the device with ZnO/Al as cathode has a current efficiency of 2.65 cd/A with Commission Internationale de l'Eclairage(CIE)coordinates at(0.31,0.31).In inverted device structure,the PEI-modified ZnO is used as the electron injection layer of the device to reduce the potential barrier for electron injection from the ZnO to the blue polymer.Preparing organic blue/red and green quantum hybrid white light devices with the current efficiency of 5.3 cd/A and turn-on voltage of 3.2 V.To the best of our knowledge,the device efficiency is the highest ever reported for organic/inorganic hybrid WQLEDs.More importantly,when the device brightness increases from 100 cd/m~2 to 10000 cd/m~2,the color coordinates change slightly,only from(0.29,0.30)to(0.32,0.34),and the EL emission spectrum is very stable.To improve the current efficiency of QLEDs,the influences of hole current density on QLEDs were investigated in the fourth part of this paper.The hole current of the device is increased by mixing high hole mobility TFB into the hole transport layer PVK.The results show that the hole current increases significantly at different mixing ratios,but the device efficiency decreases with increasing hole current.In order to eliminate the influence of the doping on the interface between the hole transport layer and the quantum dot layer,a double hole transport layers of Poly-TPD/PVK was used.The experimental results show that the device current density was improved.However the device efficiency was decreased.
Keywords/Search Tags:Organic/quantum dot hybrid, WQLEDs, Carrier injection and balance, Forster energy transfer, Carrier capture, Hole current density, Exciton Quenching
PDF Full Text Request
Related items