A subtle change in molecular structure of OLED material could lead to significant variation in device performance. For a better understanding of the connection between molecular structures and properties, four molecules (1, 2, 3, and 4) based on different spiro-systems, namely spiro[cyclopropane-1,9′-fluorene], spiro[cyclopentane-1,9′-fluorene], 1′,3′-dihydrospiro[fluorene-9,2′-indene] and spirobifluorene, were designed and prepared. The influences of different spiro units on photophysical properties and electroluminescence performance were fully studied. The experimental results showed that photophysical properties, electrochemical behaviors, and frontier molecular orbital distributions of these different spirofluorenes are mostly identical because the π-backbones were less affected by the different cycles at the C-9 position of fluorene. However, green phosphorescent organic light-emitting diodes (PHOLEDs) based on spirobifluorene derivative 4 exhibited the highest electroluminescence performance among these four hosts. Thus, we hope this work could reveal deep understanding for the rational design of host materials based on spirofluorene blocks.

OLED材料分子结构的细微变化可能导致器件性能发生重大变化。分子结构和性能，四个分子（之间的连接的一个更好的理解1，2，3，和4）基于不同的螺环系统，即螺环[cyclopropane-1,9'-芴]，螺环[环戊烷-1,9'-芴]，1'，3'-二氢螺环[芴-9,2'-茚]设计和制备了螺二芴和螺二芴。充分研究了不同螺环单元对光物理性质和电致发光性能的影响。实验结果表明，这些不同的螺芴的光物理性质，电化学行为和前沿的分子轨道分布基本相同，这是因为在芴的C-9位置，不同的环对π骨架的影响较小。但是，基于螺二芴衍生物4的绿色磷光有机发光二极管（PHOLED）在这四个宿主中表现出最高的电致发光性能。因此，我们希望这项工作能够揭示出对基于螺芴嵌段的主体材料合理设计的深刻理解。