We investigate molecular fragmentation in the long lived archetype blue PHOLED guest/host system based on iridium (III) tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f] phenanthridine] (Ir(dmp)₃) and 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl (mCBP) as a function of luminance loss using laser desorption ionization time-of-flight mass spectrometry and X-ray photoelectron spectroscopy (XPS). The blue phosphor experiences significant ligand loss due to its labile Ir-ligand bonds, whereas the mCBP host is relatively stable as the luminance decays to 40% of its initial value at 3000 cd/m². Density functional theory calculations indicate that fragments from mCBP are less likely to cause luminance loss via exciton quenching compared to those of the Ir-complex. Phosphor fragments are observed by XPS only in aged samples, and the concentration of fragments is found to increase with aging time. These findings suggest that the lifetime of blue PHOLEDs can be improved by using phosphors without labile Ir-ligand and intra-ligand bonds, and a host material that does not form large mass fragments or complexes with the degraded phosphor molecules. Insights into the origin of the loss in luminance due to trap formation from molecular fragmentation of this guest/host system during use are discussed.

我们调查基于铱（III）三[3-（2,6-二甲基苯基）-7-甲基咪唑并[1,2-f]菲啶]（Ir（dmp）的长寿原型蓝色PHOLED来宾/宿主系统中的分子碎片₃）和3,3'-二（9H-咔唑-9-基）-1,1'-联苯（mCBP）作为亮度损失的函数，使用激光解吸电离飞行时间质谱和X射线光电子光谱学（XPS）。蓝色磷光体由于其不稳定的Ir-配体键而遭受明显的配体损失，而mCBP主体相对稳定，因为亮度在3000 cd / m ^2时衰减至其初始值的40％。密度泛函理论计算表明，与Ir复合物相比，来自mCBP的碎片通过激子猝灭引起亮度损失的可能性较小。XPS仅在老化的样品中观察到磷碎片，并且发现碎片的浓度会随着老化时间的增加而增加。这些发现表明，通过使用不具有不稳定的Ir-配体和配体内键的磷光体，以及不与降解的磷光体分子形成大质量碎片或复合物的主体材料，可以改善蓝色PHOLED的寿命。讨论了由于使用过程中该客体/宿主系统的分子碎裂而形成陷阱而导致的亮度损失的根源。