基于液晶衬垫的OLED光萃取

采用旋涂的方法制备了(3,4-亚乙二氧基噻吩) :聚(苯乙烯磺酸)(PEDOT:PSS)薄膜,结合液 晶衬垫(LCS,liquid crystal spacer)对OLED进行光萃取,制备了结构为Glass/ITO/PEDOT:P SS/LCS/NPB(40nm)/Alq₃(40nm)/LiF(1nm )/Al(100nm)的OLED以及其相应的对比 器件。通过测量其电压、 电流、亮度、色坐标和电致发光(EL)光谱等参数,研究了LCS对OLED发光性能 的影响。结果表明, 当引入LCS后,OLED在电压为11V时,最大电流效率达6.15cd/A,比不加 LCS的器件提高了40%；且在电压从7V上升到12V的过程中,器件的色坐标仅从(0.31,0.57) 变化到(0.31,0.56)。究其原因,LCS的引入可以提高透过率,破坏器 件内部光的折射以及全反射条件,并使功能层形成褶皱结构,使更多的光子能够从器件内发 射,也增大了电极的表面积,使电流密度增加,注入的能量提高。

OLED light extraction based on liquid crystal spacer

The PEDOT:PSS film was prepared by using spin-coating method.Combined with th e liquid crystal spacer (LCS) as light extraction material,the OLED device with the st ructure of glass/ITO/PEDOT:PSS/LCS/NPB(40nm)/Alq₃(40nm)/LiF(1nm)/Al(100nm) and its corresponding contrast devices were prepared.By measuring the voltage,current,brightness,color coordinates,the e lectric light emission spectrum and other parameters,the influence of LCS on luminescence prope rties of the devices is studied.The maximum current efficiency of 6.15cd/A with a CIE chromaticity coordinate of (0.31,0.56) at the voltage of 11V is obtained in the device with the LCS,which is 40% higher tha n that of the OLED device without LCS.The CIE chromaticity coordinate changes on ly from (0.31,0.57) to (0.31,0.56) as the voltage increases from 7V to 12V.Reasons are that the introduction of LCS can improve transmittance and destroy the condition of light refraction and total reflection in the device.At the same time,the function layer can form into fold structure,which can make more photons emit from the device.The surface area of the electrode is increased,so the current density is increased, and the injected energy is improved.