【作者】 王军；

【导师】 蒋亚东；

【作者基本信息】 电子科技大学 ， 光学工程， 2008， 博士

【摘要】 与液晶显示、无机发光二极管或等离子体显示技术相比,有机发光二极管（organic light-emitting diodes,OLED）亦称有机电致发光器件（organicelectroluminescence devices,OELD）,具有自发光、响应快、全固态、制备工艺简单、高效率、宽视角、超薄、耐高低温、柔性等优点,可用作信息显示和照明的终端,被誉为最理想和潜力的下一代显示技术。但目前工艺不成熟导致器件制造成本较高,高性能发光材料缺乏导致器件性能待提高,发光和衰减机理认识不充分导致器件结构改善缺乏指导,这大大影响了OLED器件的产业化步伐,针对上述问题,本论文在高分辨率无源矩阵（passive matrix）器件的关键制备技术、开发新的高效磷光材料及器件性能优化、改善有机器件结构方面进行了一系列的探索性和创新性的工作,具体包括:1.直流磁控溅射系统制备用于OLED的低阻高透的氧化铟锡（ITO）薄膜,考查溅射压强、氩氧比例、退火温度、退火时间、靶基距离、溅射功率、沉积温度、退火氛围八个因素对ITO薄膜性能影响。用正交试验方法安排试验大大提高实验的效率。采用了方阻、透过率、XRD、SEM、AFM、均匀性等参数对ITO薄膜进行了详细的表征。制备ITO薄膜的优化工艺参数:溅射压强为2 mTorr、氩氧比例为16∶0.5、退火温度为427℃、基板与靶材距离为15、退火时间为1 h、溅射功率为300 W、退火氛围为真空、沉积温度为127℃。制备出的ITO薄膜方阻达到17Ω/□,在可见光区域的平均透过率为86.13%。2.光刻制备了用于高分辨率（1.8英寸,128×3×160个像素）无源矩阵驱动OLED的多层基板图案。设计和加工了四层光掩膜图案,包括铬层、ITO层、绝缘层和隔离层图案。铬层图案和ITO层图案通过普通光刻工艺流程（匀胶、前烘、曝光、显影、坚膜、腐蚀、去胶）完成。绝缘层材料使用ZKPI-305聚酰亚胺,显影出图案后需进行亚胺化过程。隔离层图案采用负性光敏聚酰亚胺ZKPI-530和正性AZ5214光刻胶两种方法实现。其中正胶试验采用图形反转工艺实现了断面呈现上宽下窄的倒梯形形状,符合自动隔离金属的要求。提出用双条隔离器来取代常用的单条隔离器,降低隔离器的制备难度,提高制备OLED的良品率。3.提出用线形蒸发源（线源）替代当前有机材料蒸发的点蒸发源,对相对基板静止线源和相对基板运动线源的蒸发膜厚进行数学计算,线源蒸镀薄膜的材料的利用率大大提高,膜厚度均匀性比点源有所改善。设计了线形蒸发源装置,此装置具有提高镀膜材料的有效利用率、增加蒸发速度和成膜均匀性、可实现多种材料的均匀掺杂等优点。4.合成了一种新型发出绿光的磷光材料（tpbi）₂Ir（acac）并对其进行了表征,将材料用于小分子和高分子OLED器件制备。小分子器件结构为:ITO/CuPc/NPB/CBP∶（tpbi）₂Ir（acac）/BCP/Alq/LiF∶Al,器件约4.4 V启亮,最高亮度为13500 cd/m²,功率效率达12 lm/W,电流效率最高为22.9 cd/A,在5～40 V电压范围内稳定性良好,并且器件在低压下Ⅰ-Ⅴ特性符合热电子发射模型。制备的聚合物器件结构为:ITO/PEDOT∶PSS/PVK/PFO+30 wt%PBD∶（tpbi）₂Ir（acac）/Ba:Al,最高发光亮度为7841 cd/m²,电流效率最高为9.95 cd/A,器件发出稳定的绿光。5.合成了一种新型发出黄光的磷光材料（t-bt）₂Ir（acac）并对其进行了表征,将（t-bt）₂Ir（acac）掺杂在CBP主体材料中,制备了4层有机层结构的磷光器件。器件的电压-电流特性随外加电压的增大,依次经过了欧姆电导区、陷阱电荷限制区和空间电荷限制区,电流机制与理论相符。质量掺杂浓度为5%的器件最高效率为9.3 lm/W,8%浓度掺杂的器件亮度最高为14360 cd/m²。制备的非掺杂结构器件具有低的效率衰减特性。用NPB作为主体材料制备了超低启亮电压的磷光器件,器件在2.5 V启亮,在3.25 V时器件亮度达到100 cd/m²,4.3 V时器件亮度为1000cd/m²,6.8 V时亮度为10000 cd/m²,掺杂材料的直接载流子捕获和主体材料的单电荷传输性是器件启亮电压降低的原因。6.采用蓝光荧光材料NPB结合发出黄光的磷光材料（t-bt）₂Ir（acac）制备白光OLED器件,结构为:ITO/NPB/CBP∶（t-bt）₂Ir（acac）/蓝色发光层/BCP/Alq/LiF∶Al。所作白光器件最高亮度为7430 cd/m²,最高功率效率为9.93 lm/W,色坐标为（0.34,0.33）,接近理想白光点。用蓝光材料GDI691代替NPB材料,器件最高亮度达到了15460 ed/m²,功率效率最高为8.06 lm/W。器件在宽电压范围5～12V（亮度167～8150 cd/m²）的发光光谱较稳定,色坐标始终处于CIE1931色坐标图的白光范围内。更多还原

【Abstract】 Comparing with LCD,LED or PDP,organic light-emitting diodes（OLED） also named as organic electroluminescence devices（OELD）,possess many advantages,e.g., self-emission,fast response,full solid device,easy abrication,high efficiency,wide view-angle,super-thin thickness,and are used as the illumination source and display,. OLED are considered as the most ideal and potential display technology in 21^st century. However,the un-consummate fabrication technology causes high device fabrication cost,shorting of high quality emission materials resulte in dissatisfactory device performance,and because of indistinct understanding about mechanism of device, improving about the device shructure and organic materials is uneasy.Aiming at those problems,some creative and systematic works have been performed in this dissert including the key fabrication technology about high resolution device with passive matrix driving method,synthesizing new emission materials to fabricate high efficiency phosphorescent OLED and designing new device structure.1.Indium tin oxide（ITO） thin film used as transparent anode for OLED was deposited on glass substrate with direct current magnetron sputtering system.There are eight parameters affecting the electrical and optical properties of ITO films and orthogonal test table L₃₂（4⁸） was used to carried out the systematic study.Sheet resistance,transmissivity,atomic force microscope,X-ray diffraction and scanning electronic microscope were employed to characterize the ITO films.The optimum parameters for sputtering ITO are:deposition pressure 2 mTorr,flow ratio of argon to oxygen 16:0.5,annealing temperature 427℃,distance between target and substrate 15, annealing time 1 h,sputtering power 300 W,annealing atmosphere pure nitrogen and deposition temperature 127℃.Sheet resistance,transmittance in visible region of the film prepared with above parameters are 17Ω/□and 86.13%,respectively.2.High resolution substrate pattern（1.8inch,128^*3^*160 pixels） used for passive matrix OLED were fabricated by wet photolithography process.Four photomasks were designed and prepared for chromium（Cr） pattern,ITO pattern,insulator pattem and separator pattern.Cr and ITO pattem recurred on substrate by normal photolithography process（photoresist coating,soft-baking,exposuring,developing,etching,photoresist stripping）.Polyimide ZKPI-305 was used as the insulator layer material after high temperature baking process.The separator layer pattern is very hard to achieve by normal process because of its reverse trapeziform shape section.Both negtive photosensitive photoresist（PR） ZKPI530 and positive PR AZ5214 were used for fabricating separator pattern.The pattern can be successfully obtained with AZ5214 using an image reverse technique process,including PR coating,soft-baking,exposing with photomask,reverse baking,flood exposing,and developing.And double separators technology instead of one was used to reduce the difficulty of fabrication process and increase the eligibility rate of separators.3.Line shape evaporation source（line source） can replace the normal dot shape evaporation source（dot source） in the organic material deposition process.The simulation results show that more uniformity thickness of organic thin films and higher utilizable rate of organic material can be obtained with still or relative kinetic line source than dot source.Also an equipment with the line source was designed,which shows some advantages including enhancing the utilizable rate of organic materials, increasing the deposition rate and co-evaporated organic films.4.Novel phosphorescent material（tpbi）₂Ir（acac） with green light emission was synthesized and doped in small molecular OLED with the structure ITO/CuPc/NPB/ CBP:（tpbi）₂Ir（aeac）/BCP/Alq/LiF:Al.The device shows a maximum luminance of 13500 cd/m²,a maximum power efficiency of 12 lm/W and a current efficiency of 22.9 ed/A.The turn-on voltage of the device is about 4.4 V and the current-voltage characteristic of the device is according with Richardon-Schottky emission model under low voltage.Polymer organic device with the phosphor doped also were fabricated with the structure ITO/PEDOT:PSS/PVK/PFO+30 wt%PBD:（tpbi）₂Ir（acac）/Ba:Al.Green light stably emit from the device at different voltages.A maximum luminance of 7841 cd/m² and current efficiency of 9.95 cd/A were obtained.5.Novel phosphorescent material（t-bt）₂1r（acac） with yellow light emission was doped in CBP host to achieve small molecular OLED with four organic layers structure. As the driving bias increasing,the current-voltage characteristic of device matches with ohm current transporting,trapped charge limited current（TCLC） and space charge limited current（SCLC） theory,respectively.The device with 5 wt%doping concentration shows a maximum power efficiency of 9.3 lm/W and a luminance of 14360 cd/m² can be attained by the device with 8 wt%doping concentration.By using ultrathin undoped layer structure,the efficiency of OLED rolls off slowly as the driving voltage increasing.When the phosphor doped in NPB host,the device has a very low turn-on voltage of 2.5 V,and shows a luminance of 100 cd/m² at 3.25 V,1000 cd/m² at 4.3 V,10000 cd/m² at 6.8 V,respectively.Charge carriers directly trapped by the doped phosphor and hole only transporting property are the main reason why the turn-on voltage became lower.6.White light emission organic devices were prepared with the yellow light emission phosphorescent material（t-bt）₂Ir（acac） combining with blue light emission fluorescent material NPB.The device with the structure of ITO/NPB/CBP: （t-bt）₂Ir（acac）/blue light emission layer/BCP/Alq/LiF:A1,shows a maximum luminance of 7430 cd/m²,a maximum power efficiency of 9.93 lm/W and Commission International de l’Eclairage（CIE） coordinate of（0.34,0.33）,which is very near to ideal white point.Using GDI691 as the blue light material instead of NPB,the device shows a max luminance of 15460 cd/m²,and power efficiency of 8.06 lm/W.The coordinates of the device emission locate at white light area of CIE chromaticity diagram under broad driving voltages of 5～12 V,corresponding to the luminance ranging from 167 to 8150 cd/m².更多还原