Research And Preparation Of All-solution Inverted Quantum Dot Electroluminescent Devices

Quantum dot light emitting diodes(QLEDs)are considered to be excellent candidates for next-generation lighting and display technologies in terms of facile color tunability,wide color gamut,high color saturation and low energy cost.With the rapid progress of fabricating QLEDs,all-solution processing technique has attracted most attention for both independence of evaporation and cost-effective and time-saving craft.Among different types of all-solution QLEDs,the device with inverted structures are more easily to be integrated on N-type amorphous silicon TFTs.Thus,the inverted devices are crucial to realize the high resolution and large size display panel.However,the state-of-art all resolution inverted QLEDs are still suffered from low light extraction efficiency and large driving voltage,which limited their application in commercial markets.Therefore,to make QLEDs go to market service,optimizing the device performance by appropriate light manipulation and interface modification are of great importance.This essay aims to elevate both optical and electrical performance of QLEDs through introducing light-coupling nanostructures and self-assembled monolayer.First,instead of Zn O nanoparticles,sol-gel Zn O are chosen to be the electron injection layer.As a result,the device production cycle and leak current are both decreased,leading to a comparable performance with Zn O nanoparticle ones.Meanwhile,the achievement of the QLED based on sol-gel Zn O has overcome obstacles on incorporating nanostructures into electron injection layer made by nanoparticles,which also makes nanostructures introduced in QLEDs possible.Then,to optimize the device optical performance to a greater degree,we incorporate nanostructures into sol-gel Zn O film by nanoimprint technology and fabricate all-solution inverted QLEDs.Our research demonstrates the light trapped in waveguided mode are extracted successfully by those nanostructures.Moreover,the device optical performance has been optimized to some extent with the promoted maximum luminance from 19450 cd/m2 to 50520 cd/m2,and higher EQE from 5.1% to 11.5%.Furthermore,the QLED electrical performance has also been enhanced by modifying Zn O interface with self-assembled monolayer MBA.With such modification methods,the work function of Zn O film has been decreased by 0.3 e V and the maximum luminous efficiency has come to 16.2 lm/W,which is only 8.5 lm/W in the standard device.At last,we combine the above-mentioned modification means on our final highperformance all-solution inverted QLEDs.The nanopatterned Zn O is modified by MBA molecule,which leads to a better QDs morphology when they are deposited on nanoimprinted Zn O surface.With a high-quality QD film,the nanostructures' light extraction impact is fully manifested.In the end,our all-solution inverted QLEDs shows a high performance with a maximum luminance of 70137 cd/m2,current and luminous efficiency of 53.0 cd/A and 29.7 lm/W,respectively,and 14.1% of EQE,which is nearly 4 times to standard devices.