Host-guest structures are used in most state-of-the-art organic light-emitting devices, with the host transporting charge and confining excitons on the guest. While the host often plays a critical role in achieving high efficiency and stability, predicting and understanding these effects is a persistent design challenge which slows the discovery of new active materials. Closely related host molecules, which differ only by several functional groups, often show drastically different degradation behavior. Here, we explore this observation for the archetypical carbazole hosts 4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and 4,4′-bis(carbazole-9-yl)-2,2′-dimethylbiphenyl (CDBP). While devices based on these hosts show similar efficiencies, CDBP-based devices show a tenfold lower lifetime than CBP devices when paired with phosphorescent or fluorescent emitters. Using optically and electrically pumped degradation tests, mass spectrometry, compositional analysis, and low-temperature phosphorescence spectroscopy, the lifetimes of devices containing CDBP are shown to correlate with the formation of intermolecular triplet excimer states. These findings suggest that candidate host molecules should be screened for excimer formation as host excimers may aggravate device degradation and lower device stability.Host-guest structures are used in most state-of-the-art organic light-emitting devices, with the host transporting charge and confining excitons on the guest. While the host often plays a critical role in achieving high efficiency and stability, predicting and understanding these effects is a persistent design challenge which slows the discovery of new active materials. Closely related host molecules, which differ only by several functional groups, often show drastically different degradation behavior. Here, we explore this observation for the archetypical carbazole hosts 4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and 4,4′-bis(carbazole-9-yl)-2,2′-dimethylbiphenyl (CDBP). While devices based on these hosts show similar efficiencies, CDBP-based devices show a tenfold lower lifetime than CBP devices when paired with phosphorescent or fluorescent emitters. Using optically and electrically pumped degradation tests, mass spectrometry, compositional analysis, and low-temperature phosphorescence spectroscopy, the ...

中文翻译：

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主体准分子形成在有机发光器件降解中的作用

主客体结构用于大多数最先进的有机发光器件，其中主体传输电荷并将激子限制在客体上。虽然宿主通常在实现高效率和稳定性方面发挥着关键作用，但预测和理解这些影响是一个持久的设计挑战，它减缓了新活性材料的发现。密切相关的宿主分子，仅在几个官能团上有所不同，通常表现出截然不同的降解行为。在这里，我们探索了原型咔唑宿主 4'-双（N-咔唑基）-1,1'-联苯（CBP）和 4,4'-双（咔唑-9-基）-2,2'-的这一观察结果二甲基联苯（CDBP）。虽然基于这些主机的设备表现出相似的效率，当与磷光或荧光发射器配对时，基于 CDBP 的设备的使用寿命比 CBP 设备低十倍。使用光学和电泵浦降解测试、质谱、成分分析和低温磷光光谱，显示含有 CDBP 的器件的寿命与分子间三重态准分子态的形成相关。这些发现表明，应筛选候选宿主分子的准分子形成，因为宿主准分子可能会加剧器件降解和降低器件稳定性。 大多数最先进的有机发光器件中都使用了主客体结构，其中主体运输对客人充电和限制激子。虽然主机通常在实现高效率和稳定性方面起着关键作用，预测和理解这些影响是一个持久的设计挑战，它减缓了新活性材料的发现。密切相关的宿主分子，仅在几个官能团上有所不同，通常表现出截然不同的降解行为。在这里，我们探索了原型咔唑宿主 4'-双（N-咔唑基）-1,1'-联苯（CBP）和 4,4'-双（咔唑-9-基）-2,2'-的这一观察结果二甲基联苯（CDBP）。虽然基于这些宿主的设备显示出相似的效率，但当与磷光或荧光发射器配对时，基于 CDBP 的设备的寿命比 CBP 设备低十倍。使用光学和电泵浦降解测试、质谱、成分分析和低温磷光光谱，...