新型蓝色荧光材料5,5',6,6'-四苯基-2,2'-联吡嗪的制备和发光性质

以乙二胺和二苯乙二酮为原料合成了5,6-二苯基-2,3-二氢吡嗪(Dpdhpz),Dpdhpz在Ir Cl3·3H2O或三氟化硼乙醚等路易斯酸作用下发生自身氧化偶联得到了5,5',6,6'-四苯基-2,2'-联吡嗪(Dbppz)。在四氢呋喃(THF)溶液中,Dbppz的光致发光(PL)为深蓝色,最大发射峰位于400 nm,CIE坐标为(0.16,0.03)。Dbppz在THF溶液中最大量子效率为89%,在聚苯乙烯薄膜(Dbppz质量分数5%)中的量子效率为78%。将Dbppz制备成器件结构为ITO/HAT-CN(5 nm)/NPB(40 nm)/Dbppz(20 nm)/Tm Py PB(40 nm)/Li F(1 nm)/Al(100 nm)的非掺杂电致发光器件。实验发现,该非掺杂器件并没有产生预期的蓝色发光,而是意外地得到了一个白光器件。我们推测产生白光发射的原因与发光层和空穴传输层之间相互作用有关。由于空穴传输层NPB的芳胺结构具有电子给体性质,而Dbppz的吡嗪结构具有电子受体结构,发光层与空穴传输层的界面发生了电子给体和电子受体的相互作用,形成了激基复合物。在电致发光(EL)光谱中,除了Dbppz发光材料在415 nm的发射外,在550 nm还出现强的激基复合物的发射。激基复合物的产生使得EL发射出现了长波长光谱,同时减弱了发光层的"本征"发光。蓝色"本征"发光与激基复合物的黄色发光构成了一个CIE坐标值为(0.27,0.33)(亮度100 cd/m2)的白光器件。器件最大外量子效率、最大功率效率和最大电流效率分别为44%、0.74 lm/W和1.04 cd/A。

Synthesis and Luminescence of New Blue Fluorescent 5,5',6,6'-tetraphenyl-2,2'-bipyrazine

5,5',6,6'-tetraphenyl-2,2'-bipyrazine (Dbppz) was synthesized by oxidation coupling of two molecules 5 ,6-diphenyl-2 ,3-dihydropyrazine which was prepared from ethanediamine and benz-il, with lewis acid as catalyst, such as IrCl3 ·3H2 O and boron fluoride ethyl ether. Dbppz shows in-tense fluorescent emission in the tetrahydrofuran ( THF) solution at λmax=400 nm, with photolumi-nescence ( PL) quantum yield of 89% in THF solution and 78% in polystyrene film doped with Db-ppz mass fraction of 5%. Non-doped electroluminescence ( EL ) devices were fabricated with a structure of ITO/HAT-CN(5 nm)/NPB(40 nm)/Dbppz (20 nm)/TmPyPB (40 nm)/LiF(1 nm)/Al(100 nm) . It is unexpected that the devices do not show blue electroluminescence ( EL) as we expect, but white EL with CIE coordinates of (0. 27, 0. 33). There are two emission peaks at 415 and 550 nm in EL spectrum. The emission peak at 415 nm is attributed to “the intrinsic emission”of Dbppz and low-energy emission at 550 nm relates to interface-interaction between hole-transpor-ting layer and emission layer. Probably, the exciplex is formed by interaction of donor molecule NPB and acceptor Dbppz, resulting in new low-energy emission and restraining the intrinsic emission of Dbppz. This white device shows maximum external quantum efficiency of 44%, maximum lumi-nance efficiency of 1. 04 cd/A and maximum power efficiency of 0. 74 lm/W.