Iridium(iii) complexes with enhanced film amorphism as guests for efficient orange solution-processed single-layer PhOLEDs with low efficiency roll-off
作者:Jun Dai、Kaifeng Zhou、Ming Li、Huiqin Sun、Yunqing Chen、Shijian Su、Xuemei Pu、Yan Huang、Zhiyun Lu
DOI:10.1039/c3dt50834j
日期:——
By introducing a phenyl substituent into the meta-site of the phenyl segment of the 2-phenylbenzothiazole ligand, two novel orange iridium(III) complexes, namely, (3Phbt)222Ir(acac) and (3OMePhbt)222Ir(acac), have been synthesized. Compared with their parent compound (bt)222Ir(acac), both of them possess much enhanced thermostability and film amorphism, making them suitable candidates as guests for high performance solution-processed phosphorescent organic light-emitting diodes (PhOLEDs). However, (4Phbt)222Ir(acac) bearing para-phenyl possesses worse processability relative to (bt)222Ir(acac) due to spontaneous crystallization stemming from the intense intermolecular interactions. Single-layer solution-processed PhOLEDs with (3Phbt)222Ir(acac) and (3OMePhbt)222Ir(acac) as guests show peak current efficiency of 17.2 cd A−1 and 15.2 cd A−1, and maximum brightness of 28 270 cd m−2 and 27 900 cd m−2, respectively. Both are greatly improved compared to the devices employing (bt)222Ir(acac) (10.2 cd A−1 and 14 350 cd m−2) and (4Phbt)222Ir(acac) (5.0 cd A−1 and 13 790 cd m−2) as phosphors. Moreover, quite low efficiency roll-off is acquired in these devices at high luminance. The much improved electroluminescence performances of these objective complexes could be mainly attributed to the presence of a rigid phenyl on the appropriate substitution site of the cyclometallate ligand, which leads to improved thermostability with compatible alleviated intermolecular interactions, and consequently enhanced film amorphism.
通过在 2-苯基苯并噻唑配体苯基段的元位上引入苯基取代基,合成了两种新型橙色铱(III)配合物,即 (3Phbt)222Ir(acac) 和 (3OMePhbt)222Ir(acac)。与母体化合物 (bt)222Ir(acac) 相比,这两种化合物的热稳定性和薄膜非晶性都大大增强,因此适合作为高性能溶液处理磷光有机发光二极管(PhOLED)的客体。然而,与(bt)222Ir(acac)相比,含有对位苯基的(4Phbt)222Ir(acac)具有更差的可加工性,这是因为强烈的分子间相互作用会导致自发结晶。以 (3Phbt)222Ir(acac) 和 (3OMePhbt)222Ir(acac) 为客体的单层溶液加工 PhOLED 的峰值电流效率分别为 17.2 cd A-1 和 15.2 cd A-1,最大亮度分别为 28 270 cd m-2 和 27 900 cd m-2。与采用(bt)222Ir(acac)(10.2 cd A-1 和 14 350 cd m-2)和(4Phbt)222Ir(acac)(5.0 cd A-1 和 13 790 cd m-2)作为荧光粉的器件相比,这两种荧光粉的亮度都有很大提高。此外,这些设备在高亮度下的效率衰减非常低。这些目标配合物的电致发光性能之所以大大提高,主要是由于环金属配体的适当取代位点上存在一个刚性苯基,从而提高了热稳定性,减轻了分子间的相互作用,进而增强了薄膜的非结晶性。