Fabrication And Research On High Efficiency And Stable Blue And White OLEDs

Organic electroluminescence?OEL?is the phenomenon of light emission from an organic material under electrical excitation.Organic light-emitting diodes?OLEDs?have been prepared through this principle by scientific researcher.OLEDs has such advantages as autoluminescence,high resolution,wide working temperature range,fast response speed,low power consumption,and realize flexible display.In recent years,commercial production has been gradually achieved,widely used in flat panel display terminal with solid lighting field.The color gamut for the OLEDs flat-panel display has completely satisfied the display standards for NTSC mode.It has huge application market prospect.However,in order to further meet the needs of a wide range of commercial applications.We need to improve its performance and reduce the cost.Fabricated methods of devices,novel materials with high-efficiency and low-cost will be studied detailly in this paper.So as to prepare OLED devices with higher performance and low cost,make it apply in large area display terminal to meet the requirements of large-scale market.This research field is involved in many fields such as optics,Org.Electron.,materials science and so on.The purpose of this paper is to use different novel organic light-emitting materials and to design efficient and stable blue and white OLEDs.Design the different scheme to study the properties of the prepared OLEDs based on novle organic materials.High performance OLEDs will be achieved based on these novel materials.The main research contents is in following file:1.This paper utilizes a novel synthesis of fluorescent optical materials PTPAPI??phenanthren-9-yl?phenyl?-1H-phenanthro[9,10-d]imidazol-2-yl)-N,N-diphenyl-[1,1'-biphenyl]-4-amine),and studies its physical photoelectric,hermal,carrier transport properties as well.In order to study the electroluminescent characteristics of PTPAPI,the device of the following structure was designed,ITO/NPB?40 nm?/PTPAPI?20 nm?/Alq3?40 nm?/LiF?0.5 nm?/Al,the experimental results show that the device has obvious emission peak at about 414 nm,which belongs to the blue emission,CIE coordinates is?0.17,0.08?,that is full compliance with the International Commission on illumination definition of the blue light.The conclusion of the new fluorescence material belongs to the blue light emitting material.By using the characteristics of blue light emission,we have prepared the better performance blue OLEDs,the structure of device is ITO/ MoO₃?10 nm?/NPB?40 nm?/TCTA?5 nm?/PTPAPI?20 nm?/Alq3?40 nm?/Al,and realize the blue light emission.The maximum luminance of the device reaches up to 7123 cd/m2,when the driving voltage is 11 V,the maximum efficiency is 3.51 cd/A and the corresponding current density is 15.13 mA/cm2,the color coordinates range varies from?0.18,0.08?to?0.17,0.07?.It is also not very big fluctuation,and has very stable blue light emission effect.2.We have used a novel D-A type organic light emitting material TPABI?N,N-diphenyl-4'-?1-phenyl-1H-benzo[d]imidazol-2-yl?-[1,1'-biphenyl]-4-amine?to study its physical optoelectronic properties and electroluminescene properties.The experiment results show that TPABI is a D-A bipolar material,which has the ability to transport holes,also has the ability to transfer electrons,the transmission performance of electronic transmission performance is higher than that of the hole.In order to study the electroluminescent characteristics of TPABI,we design the device with the structure ITO/NPB?40 nm?/TPABI?20 nm?/Alq3?40 nm?/LiF?0.5 nm?/Al,the experimental results show that the device has obvious emission peak at about 450 nm from the TPABI,which contributes to the blue emission,CIE coordinates is?0.16,0.13?,the conclusion of this novel fluorescent material belongs to blue light emitting materia.In the proof of basic carrier transport characteristic and luminescence property of TPABI,we need to improve performance blue OLEDs using of the luminescent properties of TPABI,according to the relationship between energy level and band gap,the appropriate organic electroluminescent materials was selected and optimized,so we designed a set of blue OLEDs used TPABI as emitting layer.The structure is ITO/MoO₃?10 nm?/NPB??60-x?nm?/TCTA?5 nm?/TPABI?x nm?/TPBi?10 nm?/Alq3?40 nm?/Al,When the x is 30 nm,the blue device gains the best performance,obtaining the maximum luminance of 17700 cd/m2,when the driving voltage is 11 V,and the corresponding CIE of?0.16,0.15?which belongs to the better blue emission,the maximum efficiency is 5.46cd/A,the color coordinates range varies from?0.17,0.17?to?0.16,0.15?.It is also not very big fluctuation,and has the very stable blue light emission effect.3.A quinoline zinc compounds of metal complexes BTQZn?Bis?2-thiophene-8-quinolinolato?zinc?was used as a novel organic electroluminescent material to study the loptical characteristics and electroluminescent properties.The experiment results show that BTQZn has good ability of electronic transmission.In order to study the electroluminescent characteristics of the device design of the following structures: ITO/NPB?40 nm?/BTQZn?20 nm?/Alq3?40 nm?/LiF?0.5 nm?/Al,as a single layer light emitting device,its maximum luminance can reach 1341 cd/m2,the color coordinates is stability,varying from?0.45,0.47?at 6V to?0.49,0.45?at 13 V,the color coordinates belong to the yellow light,and the material is relatively stable yellow light emitting material.The electroluminescence spectra show the device has obvious emission peak near 600 nm from the BTQZn light emission,that also proved BTQZn belong to the yellow light.Based on the yellow light characteristics of BTQZn.A non-doped high efficiency white OLEDs is fabricated,which possess double emitting layers,TPABI acts as the blue light-emitting layer,BTQZn acts as the yellow light-emitting layer,the structure is ITO/MoO₃?10 nm?/NPB?40 nm?/TCTA?5 nm?/TPABI?20 nm?/BTQZn?x=10,20,30,40 nm?/Alq3?40 nm?/Al,the performance of the device with BTQZn thickness of 20 nm is the best,it gets the maximum luminance of 10370 cd/m2 at the driving voltage for 14 V,the current efficiency is also the highest for 6.79 cd/A corresponding to the current density of 6.24 mA/cm2,the color coordinates is?0.36,0.40?that belong to the good warm white light emission.5.We fabricated OLEDs that using graphene doped in NPB?NPB:Graphene?as hole transport layer,in order to study the graphene effect on improving the efficiency of OLEDs.The structure of the device was ITO/NPB:Graphene?20 wt.%??50 nm?/Alq3?80 nm?/LiF?0.5 nm?/Al.The effect of graphene on performance of OLEDs was studied via omparing with the standard device.The study results show that the device with NPB:graphene layer presents the better performance under the same conditions,when the current density is 90 mA/cm2,the maximum current efficiency reaches 3.40 cd/A,compared with the standard device maximum efficiency increased by 1.49 times,the device reaches the maximum luminance with 10070 cd/m2 at 15 V,that increased 5.16 times than the maximum luminance of standard device.6.Cs₂CO₃ and graphene are two kinds common materials in the design of optoelectronic devices,a novel efficient electron injection layer consisting of Cs₂CO₃:graphene was used in preparing the OLEDs.The effect of Cs₂CO₃:graphene as electron injection layer on the OLEDs properties was studied.The results show that the efficiency of the device based on Cs₂CO₃:graphene as an efficient electron injection layer is higher than the device that LiF as electron injection layer,the maximum current efficiency of the device reaches 2.02 cd/A at 9.5 V,which is 2.59 times compared with the maximum efficiency of standard device,the maximum luminance of this device reaches with 7690 cd/m2 at 12 V,which is 2.07 times than the maximum luminance of standard device.The results showed that the performance of device with a electron injection layer consisting of Cs₂CO₃:graphene was improved,the main reason was that can enhance the electron electron injection.