Oligo(fluorenyl)pyridine ligands and their tris-cyclometalated iridium(iii) complexes: synthesis, photophysical properties and electrophosphorescent devices
作者:Mustafa Tavasli、Sylvia Bettington、Martin R. Bryce、Hameed A. Al Attar、Fernando B. Dias、Simon King、Andrew P. Monkman
DOI:10.1039/b507990j
日期:——
The new extended tri- and penta-fluorenylpyridine ligands Fl3Py 2 and Fl5Py 3 and their tris-cyclometalated iridium(III) complexes Ir[Fl3Py]35 and Ir[Fl5Py]36 have been synthesised and their properties compared with the known iridium(III) complex Ir[Fl1Py]34. The lowest energy (emissive) excited states of the complexes 4–6 are dominated by ligand centred (LC) π→π* triplet states, as observed for their uncomplexed ligands 1–3. The emission maximum of complex 4 is ∼546 nm with a triplet lifetime of 2.8 µs. For complexes 5 and 6 the emission maxima are both ∼566 nm with triplet lifetimes of 7.4 µs and 7.8 µs, respectively. Devices made from poly(9,9′-spirobifluorene) (PSF) as the host and doped with complexes 4–6 show good stability; the EL spectra are unchanged after repeated operation over several days. Devices containing complexes 5 and 6 exhibit higher external quantum efficiency (EQE) values. Turn-on voltages of ∼3 V, giving an EQE of 2.8% at a current density of 30 mA cm−2, with a power efficiency of 4.3 lm W−1 and electroluminescence (EL) intensity of 25 000 cd m−2 at 550 mA cm−2 were observed for ITO/PEDOT ∶ PSS/PSF ∶
6/Ca/Al devices.
我们合成了新的扩展三芴基和五芴基吡啶配体 Fl3Py 2 和 Fl5Py 3 及其三环甲基化铱(III)配合物 Ir[Fl3Py]35 和 Ir[Fl5Py]36,并将它们的性质与已知的铱(III)配合物 Ir[Fl1Py]34 进行了比较。正如在未络合配体 1-3 中观察到的那样,络合物 4-6 的最低能量(发射)激发态以配体中心 (LC) π→π* 三重态为主。复合物 4 的发射最大值为 ∼546 nm,三重态寿命为 2.8 µs。复合物 5 和 6 的最大发射波长均为~566 nm,三重态寿命分别为 7.4 µs 和 7.8 µs。以聚(9,9′-螺二芴)(PSF)为基体并掺杂了复合物 4-6 的器件显示出良好的稳定性;在重复操作数天后,EL 光谱仍保持不变。含有络合物 5 和 6 的器件显示出更高的外部量子效率(EQE)值。ITO/PEDOT ∶ PSS/PSF ∶ 6/Ca/Al 器件的开启电压为 3 V,在 30 mA cm-2 的电流密度下,EQE 为 2.8%,功率效率为 4.3 lm W-1,在 550 mA cm-2 的电流密度下,电致发光(EL)强度为 25 000 cd m-2。