TBVB用作蓝光发光层的非掺杂有机电致蓝光和白光器件

利用一种来源于PPV的发蓝光的齐聚物材料2,5,2',5'-tetra(4'-biphenylenevinyl)-biphenyl(TBVB)制作非掺杂的有机电致蓝光和白光器件。蓝光器件的结构为ITO/NPB/TBVB/Alq₃/LiF/Al,其中TBVB用作发光层;白光器件的结构为ITO/NPB/TBVB/rubrene/Alq₃/LiF/Al,其中TBVB与超薄层(平均“厚度”0.05~0.20nm)的Rubrene相结合用作发光层,二者分别发蓝光和黄光。在蓝光器件中,当TBVB的厚度为30nm时,器件发出色坐标为(0.20,0.26)的蓝光,其最大亮度和效率分别达到2154cd/m²和1.62cd/A。在白光器件中,可通过调节TBVB和Rubrene的厚度实现对器件发光色度的调节。当TBVB和Rubrene的厚度分别为10,0.15nm时,器件在亮度为4000cd/m²时发光色坐标为(0.33,0.34),非常接近白光等能点,且随着电压的变化始终处于白光区。当电压为16V时该器件达到最高亮度4025cd/m²;当电压为6V时器件有最高的效率3.2cd/A。

Blue and White Non-doped Organic Light-emitting Devices Using 2,5,2',5'-tetrakis(4'-biphenylenevinyl)-biphenyl as Blue Light-emitting Layer

The formation of intermolecular aggregation is the main reason for the phenomena that the photoluminescence (PL) efficiency of trimeric phenylenvinylene (TPV) and its derivatives, which are bright pure blue emitters, is much weaker in solid state than that in dilute solution (over 90%). In order to prevent the aggregation of TPV and achieve high-efficient emission in solid state and films, a new class of dimeric TPVs was synthesized, in which two TPVs are linked through the phenyl-phenyl bond of central phenylene ring to form a crossing dimeric structure with ~70° twisting between two TPVs planarity. The electroluminescent properties of 2,5,2',5'-tetrakis(4'-biphenylenevinyl)-biphenyl (TBVB) have been studied. According to the PL spectrum of the material, blue and white non-doped organic light-emitting devices (OLEDs) using TBVB as a blue light-emitting layer were fabricated. The structure of the blue device is ITO/NPB/TBVB/Alq₃/LiF/Al, where tris(8-hydroxyquinoline) aluminum (Alq₃), N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) and TBVB are used as electron-tansporting, hole-transporting and light-emitting layers, respectively. For the blue device with 30-nm-thick TBVB, the maximum luminances and efficiencies are 2154 cd/m² and 1.62 cd/A, respectively. The structure of white devices is ITO/NPB/TBVB/rubrene/Alq₃/LiF/Al, in which Alq₃, NPB, TBVB and an ultrathin layer of 5,6,11,12-tetraphenylnaphthacene (rubrene), which is inserted between Alq₃ and TBVB layers, are used as electron-transporting, hole-transporting, blue and yellow light-emitting layers, respectively. A fairly pure white OLED with CIE coordinates of (0.33, 0.34) at 4000 cd/m² is realized when the thickness of TBVB is 10 nm and that of rubrene is 0.15 nm. The maximum luminance and efficiency of this device are 4025 cd/m² and 3.2 cd/A, respectively.