Research On Blue Quantum Dot LEDs Prepared Based On The Full Solution Method

QDs(Colloidal Quantum Dots,QDs)is a kind of novel luminescent materials with the advantages of high fluorescence efficiency,narrow emission peak,wavelength size adjustment.etc.,Quantum Dots Light Emitting Diode LED(Quantum Dots Light Emitting Diode,QLED)which using Quantum dots as luminescent materials has many advantages,such as low energy consumption,low manufacturing cost,long life,adjustable luminescence wavelength and so on,it has great potential in the application of flat panel display and solid lighting,QLED is known as the fourth generation of lightingwhich is called the fourth generation lighting source.At present,research on QLED at home and abroad has just started,and the research on blue LED is relatively less.In this paper,ZnCdS/ZnS blue light quantum dots is used as the luminescent layer,QLED with ITO/PEDOT:PSS/Ploy-TPD+TCTA/QDs/ZnO/Al structure is prepared by all solution spin coating apart from the cathode,The photoelectric properties of the device were tested and the structure and fabrication process of each functional layer of the device were optimized.The surface of the anode ITO is treated by different processes,of which the effect on the performance of the device has been contrasted.It is found that ITO surface treatment can improve the surface work function and reduce the surface roughness,thereby improving the hole injection efficiency and reducing the open voltage of the device.The effects of modification by isopropanol and acid on the quality of PEDOT:PSS film and the performance of QLED devices had been studied.It is found that a proper amount of isopropanol can significantly improve the contact between the PEDOT:PSS solution and the ITO substrate,and the quality of film is obviously improved.In the modification process of acid,the combination of H+ in acid solution and PSS-in PEDOT:PSS is increasing the proportion of conductive PEDOT,thus the conductivity of PEDOT:PSS film is improved and then the photoelectric efficiency of the device is raised too,when the acid concentration is too high,there will be a certain degree of corrosion damage to the film and the underlayer ITO film,so as to influence on the luminescent properties of devices,when acid concentration is 0.75 mol/L,the device performance is the best,its maximum brightness can reach 1133cd/m2.The influence of the mixture ratio of Ploy-TPD and TCTA on the performance of the device has been studied too.Because of the lower HOMO level of TCTA,the barrier between the quantum dot layer and the Poly-TPD can be reduced so as to promote the hole injection.The results show that the maximum luminance of the device reachs 1357cd/m2 when the mass ratio is Ploy-TPD:TCTA(3:1).However,due to the limitation of hole transport capacity,too much TCTA entry will decrease the transmission efficiency of the hole and decrease the luminous efficiency of the device.The influence of the quantum dots luminescence layer thickness and the quantum dots of different ligands on the performance of the devices has been studied,separately.It is found that the thinner quantum dot layer is beneficial to the carrier injection and light transmission,it can reduce the internal resistance of the device,and increase the luminance of the device.In addition,short chain ligand devices shows better photoelectric properties,and short chain ligand is more beneficial to the effective injection of carriers,at the same time to decrease the distance between quantum dots and organic hole transport layer,further raising the luminous efficiency of the device through fluorescence resonance energy transfer mechanism.Based on the improved conditions prepared the best device,the device performance is good,the maximum brightness of 1716cd/m2.