Comprising hole- and electron-transporting moieties with flexible linkages, representative non-conjugated bipolar hybrids have been synthesized and characterized for a demonstration of their potential use as host materials for the fabrication of phosphorescent organic light-emitting diodes. The advantages of this material class include solution processing into amorphous films with elevated glass transition temperatures, stability against phase separation and crystallization, and provision of LUMO/HOMO levels and triplet energies contributed by the two independent moieties without constraint by the electrochemical energy gap. While exciplex formation between the hole- and electron-transporting moieties is inevitable, its adverse effects on spectral purity and device efficiency can be avoided by trapping charges on triplet emitters, as demonstrated for Ir(mppy)3 in TRZ-3Cz(MP)2, and TRZ-1Cz(MP)2. With these two bipolar hybrids and hole-transporting Cz(MP)2 as the host, the maximum current efficiency of the bilayer PhOLED is achieved with TRZ-3Cz(MP)2, but the driving voltage decreases monotonically with an increasing TRZ content.
包含具有灵活连接的孔和电子传输部分的代表性非共轭双极杂化物已经被合成和表征,以展示其作为制造
磷光有机发光二极管的宿主材料的潜在用途。这类材料的优点包括可以溶液加工成具有较高
玻璃转变温度的无定形薄膜、抵抗相分离和结晶的稳定性,以及由两个独立部分提供而不受电
化学能量间隙限制的LUMO/HOMO
水平和三重态能量。虽然孔和电子传输部分之间的激发态复合物形成是不可避免的,但通过在三重态发射体上捕捉电荷,可以避免其对光谱纯度和器件效率的负面影响,正如在TRZ-3Cz(MP)2和TRZ-1Cz(MP)2中对Ir(mppy)3的展示所示。使用这两个双极杂化物和孔传输材料Cz(MP)2作为宿主,双层
磷光有机发光二极管的最大电流效率通过TRZ-3Cz(MP)2实现,但驱动电压随着TRZ含量的增加而单调降低。