Centre for Organic Photonics & Electronics, The University of Queensland, School of Chemistry & Molecular Biosciences, QLD 4072, Australia.
J Am Chem Soc. 2009 Nov 25;131(46):16681-8. doi: 10.1021/ja903157e.
Solution-processable blue phosphorescent emitters with high luminescence efficiency are highly desirable for large-area displays and lighting applications. This report shows that when a fac-tris[1-methyl-5-(4-fluorophenyl)-3-n-propyl-1H-[1,2,4]triazolyl]iridium(III) complex core is encapsulated by rigid high-triplet-energy dendrons, both the physical and photophysical properties can be optimized. The high-triplet-energy and rigid dendrons were composed of twisted biphenyl dendrons with the twisting arising from the use of tetrasubstituted branching phenyl rings. The blue phosphorescent dendrimer was synthesized using a convergent approach and was found to be solution-processable and to possess a high glass transition temperature of 148 degrees C. The dendrimer had an exceptionally high solution photoluminescence quantum yield (PLQY) of 94%, which was more than three times that of the simple parent core complex (27%). The rigid and high-triplet-energy dendrons were also found to control the intermolecular interactions that lead to the quenching of the luminescence in the solid state, and the film PLQY was found to be 60% with the emission having Commission Internationale de l'Eclairage coordinates of (0.16, 0.16). The results demonstrate that dendronization of simple chromophores can enhance their properties. Single layer neat dendrimer organic light-emitting diodes (OLEDs) had an external quantum efficiency (EQE) of 0.4% at 100 cd/m(2). Bilayer devices with an electron transport layer gave improved EQEs of up to 3.9%. Time-resolved luminescence measurements suggest that quenching of triplets by the electron transport layer used in the bilayer OLEDs limits performance.
具有高光致发光效率的溶液处理型蓝色磷光发射器对于大面积显示器和照明应用非常理想。本报告表明，当一个 fac-tris[1-甲基-5-(4-氟苯基)-3-正丙基-1H-[1,2,4]三唑基]铱(III) 配合物核被刚性高三重态能量树枝状大分子包裹时，其物理和光物理性质都可以得到优化。高三重态能量和刚性树枝状大分子由扭曲的联苯树枝状大分子组成，扭曲是由于使用了四取代支化的苯基环。蓝色磷光树枝状大分子通过收敛方法合成，发现其可溶液加工，玻璃化转变温度高达 148°C。该树枝状大分子具有非常高的溶液光致发光量子产率（PLQY），为 94%，比简单的母体核配合物（27%）高出三倍以上。刚性和高三重态能量树枝状大分子也被发现可以控制分子间相互作用，从而导致在固态下发光猝灭，薄膜 PLQY 为 60%，发射出的颜色具有国际照明委员会（Commission Internationale de l'Eclairage）坐标（0.16,0.16）。结果表明，简单发色团的树枝化可以增强其性质。单层纯树枝状大分子有机发光二极管（OLED）在 100 cd/m²时的外量子效率（EQE）为 0.4%。具有电子传输层的双层器件可将 EQE 提高至 3.9%。时间分辨发光测量表明，在双层 OLED 中使用的电子传输层对三重态的猝灭限制了性能。
