Novel Oligomers of 9,9-Dialkylated Fluorenes for Thermally Stable Hole-Transport Materials in OLEDs

Abstract

Using 9,9-dialkyl-functionalized fluorenes as monomers, novel fluorene-based oligomers were prepared in order to improve the thermal stability of a typical hole-transport material (HTM), N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), in organic light emitting diodes (OLEDs). 2,7-Bis(diphenylamino)fluorene was utilized as a TPD unit throughout the present synthetic work. 9,9-Bis(2-methylallyl)fluorene and its TPD congener underwent a new cyclopolymerization reaction affording six-membered oligomers under acid catalysis with p-toluenesulfonic acid. Intermolecular Suzuki coupling of a 9,9-bis(p-bromobenzyl)fluorene analogue with the corresponding bis-boronate afforded a new oligomer containing the TPD substructure. These oligomers (3 and 6) for use as HTMs have high glass-transition temperatures (Tg’s) (147 and 167 °C, respectively); the values are much higher than the Tg for TPD (63 °C). These materials are soluble in organic solvents to allow easy processing for preparing layered devices, though their electroluminescent performances were lower than that of the single molecule TPD.

Aerobic Oxidation of 9H‐Fluorenes to 9‐Fluorenones using Mono‐/Multilayer Graphene‐Supported Alkaline Catalyst

“…[24,25] All other inorganic reagents and organic solvents were purchased from Tianjin Chemical Co. All chemicals were analytical grade and used as received. 2,7-Dibromo-7-nitro-9H-fluorene and 2,7-bis(diphenylamino)-9H-fluorene were synthesized by using published procedures to give product with purify greater than 98 %.…”

“…25 [26] Ultraviolet/visible (UV/Vis) spectroscopy analysis UV/Vis absorption spectra were recorded with a Lambda 1050 UV/ Vis/NIR spectrophotometer (PerkinElmer) using a quartz cell with a 1 cm optical path. The AFM tip (Tetra15/Au/15, Nanotechnology LLC.)…”

“…2,7-Dibromo-7-nitro-9H-fluorene and 2,7-bis(diphenylamino)-9H-fluorene were synthesized by using published procedures to give product with purify greater than 98 %. [24,25] All other inorganic reagents and organic solvents were purchased from Tianjin Chemical Co. All chemicals were analytical grade and used as received.…”

Control of Charge-Carrier Mobility via In-Chain Spacer Length Variation in Sequenced Triarylamine Functionalized Polyolefins

“…2,7-Bis(phenyl-m-toluylamino)fluorene (TPF) was chosen as the hole transporter in this study because it is structurally identical to the commonly used hole transporting material 4,4′-Bis(phenyl-m-toluylamino)biphenyl (colloquially called triphenyldiamine, TPD), except that TPF contains an aryl ring bridging methylene unit that allows for easy decoration with polymerizable groups. 26 Furthermore, we anticipated the potentially poor solubility of our target polymers, thus the m-toluyl derivative of TPF was chosen, as opposed to the tetraphenyl alternative, because we expected the former variant would suffer solubility issues to a lesser extent. Our worries proved founded for polymer PE9TPF, as will be addressed below.…”