Highly Efficient And High-Color-Quality Hybrid White Organic Light-Emitting Diodes

White organic light-emitting diodes?WOLEDs?are considered to be the most promising candidate for the future indoor lighting because of their unique advantages of surface light source,light and thin,flexible and can be used for large-scale fabrication,etc.To realize commercial lighting applications for WOLEDs,device efficiency and color quality are the most important factors.However,the most reported high-color-quality WOLEDs in current literatures are widely suffered from some disadvantages such as low device efficiency,complicated device structure and fabrication process,which are not conducive to their commercialization.Therefore,we designed a series of novel devices to realize effective management and utilization of carriers and excitons,and successfully developed three kinds of hybrid WOLEDs with high efficiency and high color quality.Detailed research contents are as follows:1.A highly efficient and high-color-quality hybrid WOLED was fabricated by combining emissions from phosphorescent doped layer and phosphorescent ultrathin layer.Blue fluorescent material Bepp₂,possessing high fluorescence quantum yield(?_PL=80%)and high triplet energy level?T₁=2.6 eV?,was selected as the blue emitting layer?EML?.The effectively manage and utilize on generated singlet and triplet excitons was achieved by introducing complementary-color phosphorescent doped layers and ultrathin layer at different positions of this device.Through the optimization of device structure,a high-efficiency four-color hybrid WOLED was prepared with the maximum current efficiency,power efficiency and external quantum efficiency reached 34.15 cd/A,29.51 lm/W and17.71%,respectively.This device also exhibited high-color-quality warm white light emission with high CRI of 94 and low CCT?<2500 K?.2.A highly efficient and high-color-quality hybrid WOLED was developed by employing full phosphorescent ultrathin-layer structure.On the basis of previous work,to further simplify the device structure,ultrathin green,yellow,and red phosphorescent layers?<0.1 nm?were inserted into the Bepp₂ blue EML with a certain thickness of interlayer,then a series of four-color undoped fluorescent/phosphorescent hybrid WOLEDs with high efficiency and high color quality were fabricated by adjusting different sequences of phosphorescent ultrathin layers.The maximum current efficiency,power efficiency and external quantum efficiency of optimized WOLED are up to 32.19 cd/A,30.65 lm/W and19.34%,respectively.Furtherly,this device also displayed great color quality.With the increasing of driving voltage from 5 V to 9 V,the emission spectra of this device remain stable,accompanied by CRI and CCT were maintained at 95-96 and 2300-2600 K,respectively.3.A highly efficient and high-color-quality hybrid WOLED was developed by combining the blue light emission from hole and electron transporting layer.Using a deep-blue material 4P-NPD with higher fluorescence quantum yield(?_PL=92%),high-efficiency bilayer deep-blue device based on the simultaneous emissions of 4P-NPD and Bepp₂ was designed.The optimized blue device showed the peak wavelength at 432 nm,the maximum brightness and external quantum efficiency of 14140 cd/m² and 5.07%,respectively.Based on this high-efficiency blue device,by reasonably doping green,yellow and red phosphorescent materials into 4P-NPD and Bepp₂,a series of two-color,three-color and four-color hybrid WOLEDs were prepared.The maximum external quantum efficiencies for the corresponding devices reached 18.87%,15.49%and18.44%,respectively.In addition,the optimized four-color hybrid WOLED achieved high CRI of 94 and low CCT??3000 K?,which may make it an alternative ideal indoor lighting source.