Simplified Low Power Consumption White Organic Light-emitting Device

In recent years,one device that is on the cusp of widespread use is the organic light-emitting device(OLED).OLED-based display products,such as Samsung's AMOLED mobile phones,LG's ultra-thin OLED TVs,Sony's VR helmet displays,have already been commercialized,and there is significant effort under way to make laptop monitors and eventually intelligent wearable devices using OLED technology.OLED are now also being considered as efficient solid-state lighting sources.Over the last three decades,the activities on OLEDs turn to focus on the development of the commercial products,derived from the monotonously fundamental research.More effort should be made to satisfy the requirements of longevity,low-cost and high efficiecny.As known that,interest in the application of white OLED(WOLED)technology for general flat panel displays and solid-state lighting applications has already been steadily increasing.In this contribution,the solutions to fabricate WOLEDs with simplified structures and low power consumption are suggested.Although the challenges(cost,efficiency,out-coupling efficiency,operational stability)facing WOLEDs are significant,we are optimisitic that this technology will meet practical goals and expectations in the near future.The main research achievements involved in this dissertation are listed as follows:1.We report on bottom-emitting single-host WOLEDs based on 26 DCz PPy.High efficiency simplified WOLED based on 26 DCz PPy by utilizing FIrpic as assistant dopant to boost energy transfer from 26 DCz PPy to PO-01 is obtained.The bipolar nature of 26 DCz PPy and the well matched frontier molecular orbital energy levels allows a balanced carrier injection into the emitting layer.The optimized device,without any out-coupling enhancements,obtains a current efficiency(CE)of 39 cd/A and power efficiency(PE)of 30 lm/W at 4 V(431 cd/m2)corresponding to an EQE of13.7%.The CIE of the optimized device only shows a slight shift from(0.35,0.45)to(0.34,0.43)over the illumination-relevant luminance range of 100-10000 cd/m2.2.From the perspective of new materials,we report on efficient WOLEDs based on a novel phosphine oxide host,4,6-bis(diphenylphosphoryl)dibenzofuran(DBFDPO).Carbazolyl moieties are introduced at 2,8-positions of DBF,while DPOs bond to DBF along molecular short axis.It's an excellent host for blue emitter for high lowest triplet-excited states(T1)of 3.16 e V,and the high glass-transition temperature(Tg)could improve the operational stability.We have achieved efficient WOLED with max CE of 41.3 cd/A,PE of 34.0 lm/W at 673.4 cd/m2 and low turn-on voltage of 2.5 V.Furthermore,Ir(Bt)2(acac is introduced for improve the color stability and CRI.The CIE of the optimal WOLED merely shift(±0.03,±0.05)over a wide range of luminance(10-10,000 cd/m2)and the CRI increase to 67.We found that the effect of carrier-trapping and carrier-assist transport impact critically on the spectra stability.Meanwhile,a thin Ir(ppz)3 interlayer could manipulated the dynamic distribution of carriers and excitons so as to obtain balanced white emission and improve the efficiency.3.We research on the operational stability through tandem WOLED,Libpp is employed as a novel EIL,which has low evaporating temperature and weak water oxygen sensitivity.Highly efficient and low power consumption WOLEDs based on ultrathin nondoped phosphorescent emissive layers have been reported.We work out simplified structure of HTL/Dopant ultra-thin layer/HTL or ETL/ Dopant ultra-thin layer /ETL.A series of carrier transfer materials are introduced.The optimized device employ Tc Ta as hole transport layer,B3 PYMPM as electron transport layer as well as interlayer,which is used for seperating the different ultra-thin emission layers.Tc Ta and B3 PYMPM both have high T1 levels.The max CE and PE are over 40 cd/A and40 lm/W,respectively.We alos report hybride WOLEDs utilizing excimer emission.The greatest merit of ultrathin nondoped phosphorescent EML is extremely simplified device structure and minimal material usage.4.Low power consumption and high efficiency simplified top-emitting WOLEDs are reported.We demonstrated that the exciplex forming by codoped Tc Ta and B4 PYMPM is an efficient host for yellow phosphorescent emitter.Withoutintroducing additional host materials,out top-emititng WOLED achieved a low turn-on voltage of 2.4 V,and the max CE and PE is 29 cd/A and 27 lm/W.The EQE is5.7%?8.2% and 6.5% according to the luminance of 100 cd/m2?1000 cd/m2 and 5000cd/m2,respectively.We also proved that the performance will be further improved by growing an optical capping layer(60 nm Tc Ta)on top of Cu cathode.Based on the research of WOLEDs,we successfully developed silicon-based(standard CMOS,Al is interconnection metal)SVGA white organic microdisplay.Furthermore,we reveal an helmet microdisplay prototype.