A series of carbazole substituted spiro[fluorene-9,9′-xanthene] (SFX) derivatives, namely SFX-2-Cz, SFX-2′-Cz, SFX-3′-Cz, SFX-2,7-DCz, SFX-2′,7′-DCz and SFX-3′,6′-DCz, were designed and prepared as hosts for phosphorescent organic light emitting diodes (PhOLEDs). All the target compounds exhibited excellent thermal stability, especially for the substitution onto the 3′,6′-position of SFX (SFX-3′,6′-DCz, up to 500 °C). The results of low temperature phosphorescence show that the triplet energy level (T₁) will be reduced when the carbazole group is attached to the fluorene unit of SFX; however, the T₁ is nearly intact when carbazoles were introduced into the xanthene moiety of SFX. In the following investigation of blue, green, and red PhOLEDs based on these SFX-carbazole hosts, all the host materials could realize effective energy transfer to dopant phosphors under electric field excitation. For the blue PhOLEDs, the SFX-3′,6′-DCz-based device reached the maximum current efficiency (CE) of 9.7 cd A⁻¹, power efficiency (PE) of 6.4 lm W⁻¹ and external quantum efficiency (EQE) of 5.1% due to high T₁. However, the SFX-2′-Cz-based green PhOLED and the SFX-2,7-DCz-based red PhOLED show better performance of 28.2 cd A⁻¹, 24.7 lm W⁻¹, 8.5% and 17.4 cd A⁻¹, 15.6 lm W⁻¹, 10.1%, respectively, attributable to their well-matched frontier molecular orbital energy levels with the corresponding phosphorescent dopants. This work provides a systematic scheme for the rational design of efficient SFX-based hosts by carbazolyl functionalization.

中文翻译：

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螺芴并蒽吨基咔唑基质材料的合成及光电性能

一系列咔唑取代的螺[芴-9,9'-吨]（SFX）衍生物，即SFX-2-Cz，SFX-2'-Cz，SFX-3'-Cz，SFX-2,7-DCz，SFX-2'，7'-DCz和SFX-3'，6'-DCz被设计和制备为磷光有机发光二极管（PhOLED）的主体。所有目标化合物均表现出优异的热稳定性，尤其是取代SFX（SFX-3'，6'-DCz，最高500°C）的3'，6'-位置。低温磷光的结果表明，当咔唑基团连接到SFX的芴单元上时，三重态能级（T ₁）将降低。但是，T当将咔唑引入SFX的an吨部分时，图₁几乎是完整的。在以下基于这些SFX-咔唑主体的蓝色，绿色和红色PhOLED的研究中，所有主体材料都可以在电场激励下实现有效的能量转移到掺杂磷光体。对于蓝色PhOLED，基于SFX-3'，6'-DCz的器件达到9.7 cd A ^-1的最大电流效率（CE），6.4 lm W ^-1的功率效率（PE）和外部量子效率（EQE） ）（由于T ₁高）导致的5.1％）。但是， SFX-2'-CZ为基础的绿色PHOLED和SFX-2,7-DCZ为基础的红色PHOLED显示28.2光盘的性能更好^-1，24.7流明w ^^-1，8.5％和17.4光盘^-1，15.6流明w ^ ^-1，分别为10.1％，归因于与对应的磷光掺杂剂的良好匹配的前沿分子轨道的能级。这项工作为通过咔唑基功能化合理设计高效基于SFX的宿主提供了系统的方案。