Research On High-Performance Blue Quantum-Dot Light Emitting Diodes

Light emitting diodes(LEDs)have been widely used in lighting and display fields.With the development of technology,LEDs are developing towards high brightness,high color saturation,energy saving and environmental protection.Since the discovery of quantum dots,they have attracted wide attention due to their saturated luminescence color,high subordinate field luminescence effect and strong luminescent groups,which have laid the foundation for their application in semiconductor light-emitting diodes.The performance of blue quantum dots LED is inferior to that of red and green quantum dots LED,because the HOMO energy level of the blue quantum dot material is lower than that of the red and green quantum dot materials.Therefore,there is a large energy level barrier between the quantum dot and the hole transport layer,which makes it difficult to inject holes from the hole transport layer to the quantum dot.In this paper,quantum dots and Poly-TPD are used as blue luminous layer and hole transport layer(HTL),respectively.High-performance blue QLEDs are demonstrated by inserting a thin deoxyribonucleic acid(DNA)buffer layer between hole transport layer and ZnCdS/ZnS core/shell QDs layer.This DNA buffer layer can effectively enhance the hole injection efficiency,meanwhile its high lowest unoccupied molecular orbital(LUMO)level can help the injected electrons to be confined in the emitting layer,thus ensuring the charge balance in the QDs layer and excellent recombination efficiency.To avoid the complicated process of evaporation,the device is fabricated by spin-coating except electrode layers.Finally,blue quantum dot LED devices with excellent photochromatic purity with brightness above 16000 cd/m2 and current efficiency above 2.3 cd/A have been obtained.In addition,to take the advantages of reverse device structure,CdZnS/ZnS quantum dots were used as blue light emitting material to fabricate reverse devices based on ITO/ZnAlO/QDs/PVK/PEDOT:PSS/Al structure.Compared with the forward structure device,the reverse structure device has brightness of more than 37000 cd/m2 and current efficiency of more than 5 cd/A.The excellent device performance lays a foundation for the commercial use of blue-light QLEDs.