The Synthesis Of CdSe-based Core Shell Quantum Dots And The Performance Study In Their Electroluminescent Light-emitting Diodes

As is well known,with a series of excellent optical properties including the tunable emission color,high fluorescent efficiency,great color purity and so on,quantum dots(QDs)has become the focus of full attention,and obtained widespread researches and applications in the field of display,lighting,as well as biological imaging.As a emerging technology in the area of display,the quantum dot light-emitting diode(QLED)inherits the speciality of high color purity of QDs,making the color gamut of RGB QLEDs exceed that of the high definition television substantially,thus the QLED-based display screen enables to exhibit the color more beautiful and brighter.Furthermore,with the characteristics of self-luminescence,wide angle of visibility,and the capability of curving,the QLED is regarded as the next generation of display technology.With the development of above 20 years,the performance of QLED has enhanced much,and is moving toward practical utilization.Among the optimal performance of QLEDs,PVK and ZnO are respectively hole transport layer and electron transport layer prevalently utilized.However,the combination of PVK/ZnO NPs has some drawbacks:(1)For the QDs emitting short wavelength light,there is apparent charge injecting barrier between charge transport layer and QDs layer,limiting the injection efficiency of charge;(2)the electron mobility of ZnO NPs is 3 orders of magnitude larger than the hole mobility of PVK,which is easy to cause poor charge transport balance,then leading to the charging,quenching and auger recombination of QDs,as well as to limit the luminance and efficiency of QLEDs.So in this thesis,we've made efforts to enhance the performance of QLEDs based on the combination of PVK/ZnO NPs.1.We doped Mg into ZnO NPs,tuned the energy gap and the conduction band of ZnO,thus decreasing the electron injection barrier between ZnO layer and QDs layer and improving the luminance and efficiency of QLED.As a result,when the doped concentration of Mg was 5%,the maximum luminance was 8511cd/m2,2.25 times larger than that of ZnO based QLED.When the doped concentration of Mg was 10%,the maximum EQE was 5.9%,2.6 times larger than that of ZnO based QLED.And we had analyzed the reason for performance improvement of QLED through UPS test and electron-only devices.2.We blended the PVK with respectively Poly-TPD,TCTA and CBP which are organic materials with relative higher hole mobility,increased the hole mobility of hole transport layer,optimized the charge balance and enhanced the performance of QLED.What's more,we systematically studied the effect of the change of hole mobility on the current density,turn voltage,luminance and efficiency of QLEDs.In conclusion,we optimized the performance of PVK/ZnO based QLEDs,and improved their luminance and efficiency.