The Preparation And Optoelectronic Properties Of Novel Spiro-Fluorene Unctionalized Organic Semiconductors

Spiro-fluorene functionalized organic semiconductors, what are widely used in organic light-emitting didodes (OLEDs), can improve their thermal and morphological stability and quantum efficiency dramatically, and further promote device efficiency and prolong operation lifetime. In this dissertation, in order to obtain highly efficient luminescent materials, a great many of novel spiro-fluorene functionalized organic semiconductors have designed and synthesized, and their material properties and device performance are also systematically studied.1. To study the influences of different steric hindrance groups on thermal stability, optophysical and electrochemical properties, film morphologies and device performance, further systematically investigate materials’structure-property relationships, we reasonably designed molecular structures and systematically synthesized different steric hindrance functionalized pyrene derivatives. After a great deal of investigation, we found that steric hindrance groups have little influence on absorption and emission in solutions, and electrochemical properties among the pyrene derivatives possessed the same conjugated backbone. While, in aggregated film state, all pyrene derivatives could form smooth and pin-hole free thin films and the morphology is amorphous. The significant differences between pyrene derivatives can be attribute to the different steric hindrance groups which lead to various interesting phenomena in aggregation state.2. Solution processable spiro[fluorene-9,9-xanthene]-functionalized pyrene-based blue light-emitting materials, OSFXPy and DOSFXPy, were successfully designed and synthesized, and their thermal, physical and electrochemical properties and morphologies are investigated via TG, DSC, CV and AFM. It reveals that disubstituted pyrene DOSFXPy has higher thermal and electrochemical stability, and better film-forming ability than that of monasubstituted pyrene OSFXPy. Solution processable nondoped OLEDs based on DOSFXPy and OSFXPy have an optimal current efficiency of2.07and0.7cd/A, respectively. So it can be saying that the use of bulk hindrance of3,6-dioctyloxy spiro-[fluorene-9,9-xanthene] to modify1,6-position of pyrene can effectively improve material’s optoelectronic properties.3. Successfully designed and synthesized, and investigated organic light-emitting transistor properties of spiro-fluorene functionalized anthracene derivatives. We found that2-(anthracen-2-yl)-spiro[fluorene-9,9’-xanthene](2-AnSFX) possesses the best p-type carrier transporting characteristic among them. The average carrier mobility and threshold voltage are1.0×104cm2V-1s-1and29.7V, respectively. With the increasing of steric structure of spiro-fluorene or prolonging conjugated length, the mobility decrease sharply. In the single cystal of2-AnSFX, the C-H...π distance of anthracene moiety is2.789A, it has strongly molecular interaction and carriers can hop and transport easily between molecules, so2-AnSFX has higher carrier mobility.