The Design, Synthesis, And Applications Of Steric Hindrance Fluorenyl Based Luminescent Materials

Organic light-emitting diodes (OLEDs) have attracted increasing attentions fortheir application as flat-panel displays and solid-state lighting technology since theseminal works first reported by Tang and his co-workers, due to their light weights,wide-viewing angles, high contrast, wide and cheap raw material source,self-emission properties, flexible large-area, fast response times, and so on. Manyphosphorescent and fluorescent emitters based devices have been developed to meetthe demands of full-color display. Moreover, the phosphorescent organiclight-emitting diodes (PhOLEDs) are of great interest to achieve high performancedevice due to their100%internal quantum efficiency in theory caused by heavymetals. To fabricate high-efficiency devices, two key approachs are necessary, one isto explore high-performance phosphorescent emitters; the other is to synthesizesuitable host materials. In this paper, a series of9-(pyridine-2-yl)-9H-fluoren-9-ol andspiro[fluorene-9,9’-xanthene] derivatives based host and phosphorescent guestmaterials have synthesized successfully to produce high performance devices.1. The synthesis, photophysical and electrical properties research oflight-emitting materials based on9-(pyridine-2-yl)-9H-fluoren-9-ol throughFriedel-Crafts Reaction to build host materials9,9–Diarylfluorenes have stable morphology and high thermal stability propertiesand can effectively suppress the concentration quenching and triplet annihilation ofphosphorescent materials at high concentration because of their three-dimensionalbulky steric effects. In addition, fluorene has high triplet energy level (2.95eV) andcould be modified easily at the9-position to ensure high triplet level as well as goodoptical and electrical properties because of non-conjugated connection. Based on thisidea, a concise synthesis and electrophorescent host materials of pyridine-baseddiarylfluorenes via Friedel-Craft Reaction for highly efficient red, green, and bluethree primary color-based phosphorescent devices have been successfully carried out,the maximum external quantum of which are8.9％,11.1％and10.5％, respectively.All of the research results indicate the introducing of9-(pyridine-2-yl)-fluoren-9-ol unit into the compounds could enhance the injection of electron and hole, which isexpected to fabricating low driving voltage and high performance phosphorescentdevice.2. The synthesis, optical and electrical properties research of quinoline/spiro-9,9-xanthene bipolar moleculesIn this section, a series of spiro[fluorene-9,9’-xanthene]/quinoline hybride bipolarmolecules have been designed and synthesized successfully, whose UV absorptionand fluorescence spectra in dichloromethane solution almost have no change with thevariation of the number and location position of the quinoline units but haveobviously red shift in the solid film compared with the corresponding spectra insolution. In addition, they also have good morphological, thermal stability as well assuitable triplet energy because of their3-D bulky steric hindrance and tune theirelectron transportation by introducing several quinoline unites at different positions,which could make them transport hole and electron simultaneously and balancecarriers to enlarge the carrier confinement zone for high performance devices. In thissection, three kinds of primary color red, green and blue phosphorescent devices havebeen fabricated based on the three compounds as host materials, whose maximumexternal quantum efficiency are9.1%,6.3%and0.21%, respectively.3. The synthsis, optical and electrical properties research of three dimensionalspiro-functional Ir(III) phosphorescent complexesIn this section, two different ligands of2-(spiro[fluorene-9,9’-xanthene-2-yl]-pyridine (PySFX) and (pyridine-2-yl)-9H-fluoren-9-ol (PyFOH) have beensuccessfully designed and synthesized. To build two different spiro-functionalizedphosphorescent iridium (III) complexes, the spirometal functional complexes(PySFX)2Ir(PyFO) and spiro-functional ligand (PySFX)2Ir(acac)(acac=acetylacetone) have been designed and synthesized. Their structures werecharacterized by1HNMR and13CNMR, and optimized by TDDFT calculation toresearch the relationship between the molecular frontier orbital and structure in theory.Their thermal and morphological stabilities were characterized and analyzed by theirTGA and DSC curves to study the influence of the spiro-annulationed structure, and their spectral and electrochemical properties were also examined and analyzed tostudy the relationship of their optical properties and structure between the twodifferent spiro-annulationed organometallic compounds.4. The synthsis, optical and electrical properties research of three dimensional3-dimensional spiro-annulated material containing platinum(II)In this section, spirometal annulation is introduced into platinum(II) complex that isexpected to prevent intermolecular interactions and achieve high performance devices.Bulky spirometal annulation is an alternative to control Pt-Pt distance effectively tosuppress excimer emission. A spiro[fluorene-9,9’-xanthene](SFX) functionalized Ptcomplex has been synthesize as a model to further utilize the SSH effect that derivesfrom both spiro-annulated metals and spiro-annulated ligands. Our devices exhibitedorange emission with a current efficiency of16.0cd A-1and a maximum externalquantum effciency of5.2%.