热稳定空穴传输材料的合成及其电致发光器件

合成了两种NPB的新衍生物:N,N’-二(1-萘基)-N,N’-二(4-甲基苯基)-1,1’-联苯-4,4’二胺(NTB)和N,N’-二(1-萘基)-N,N’-二(4-叔丁基苯基)-1,1’-联苯-4,4’二胺(NBB)。DSC测得其玻璃态转变温度分别为108℃和129℃,表现出好的热稳定性。紫外光电子能谱测得其电离势均为5.2eV。NTB和NBB固体光致发光光谱的最大发射波长分别位于455nm和460nm。分别以NPB、NTB、NBB作为空穴传输层材料(HTM)制作了结构相同的有机电致发光器件,3种器件发光光谱相同,均为Alq₃的绿色发光,器件的起亮电压分别为11,9,8V,在15V工作电压时的亮度分别为1000,1300,1200cd/m²,初步研究了器件的发光特性和稳定性。

Synthesis of Thermal Stable Organic Hole Transporting Materials for Use in Electroluminescent Devices

Organic electroluminescence is one of the most promising technology for next generation of flat panel display.Hole transporting layer represents the weakest link in the electroluminescent structure considering the thermal stability of the materials.The most widely used hole transporting material, N,N’-bis (1-naphthyl)-N, N’-diphenyl-1, 1’-biphenyl-4, 4’-diamine (NPB), has a glass transition temperature (T_g) of 95℃, which is much lower than that of the electron transporting material, tris (8-hydroxyquinoline) aluminum (Alq₃).Based on the good hole transporting property and suitable energy level matched with other materials of NPB, two new hole transporting materials: N, N’-bis(1-naphthyl)-N,N’-di(4-methylphenyl)-1,1’-biphenyl-4, 4’-diamine (NTB) and N, N’-bis(1-naphthyl)-N, N’-di(4-tert-butylphenyl)-1, 1’-biphenyl-4, 4’-diamine (NBB) were synthesized by introducing methyl and tert-butyl groups into NPB to improve its thermal stability.The glass transition temperature (T_g) of NTB and NBB measured by DSC are 108℃ and 129℃ respectively, showing better thermal stability than that of NPB.The ionization energy obtained by ultraviolet photoemission spectroscopy is 5.2eV for all of NPB and its derivatives.The emission peak in the photoluminescent spectra of the solid films of NTB and NBB are at 455nm and 460nm, which are close to the emission peak of NPB at 440nm.The organic electroluminescent devices using NPB, NTB and NBB as hole transporting layer (HTM) were fabricated with the structure of ITO/CuPc(20nm)/HTM(50nm)/Alq₃(60nm)/LiF(0.5nm)/Al(100nm).The emission spectra of the three devices are the same and the green color light was emitted from the Alq₃ layer.The turn-on voltages of the devices are 11, 9, 8V for NPB, NTB and NBB, respectively.The brightness of the devices at 15V are 1000, 1300, 1200cd/m² for NPB, NTB and NBB.The devices with NTB and NBB also show better longevity than that of NPB in a prelimin ary test.