Full Emission Color Tuning in Bis-Dipolar Diphenylamino-Endcapped Oligoarylfluorenes

Abstract

A novel series of monodisperse bis-dipolar emissive oligoarylfluorenes, OF(2)Ar-NPh, bearing an electron affinitive core, 9,9-dibutylfluorene as conjugated bridges, and diphenylamino as end-caps was successfully synthesized by a convergent approach using palladium catalyzed Suzuki cross-coupling. The results of optical and electrochemical investigations showed that the HOMO, LUMO, and energy gap of these diphenylamino endcapped oligoarylfluorenes can easily be modified or tuned by the use of various electron affinitive central aryl cores that included dibenzothiophene, phenylene, oligothiophenes, 2,1,3-benzothiadiazole, 4,7-dithien-2-yl-2,1,3-benzothiadiazole, thiophene S,S‘-dioxide, and dibenzothiophene S,S‘-dioxide as well as the extent of the π-conjugated core. As a result, their emission bands measured in chloroform can cover the full UV−vis spectrum (from 412 to 656 nm). In contrast to the common dipolar chromophores, most of OF(2)Ar-NPhs can form morphologically stable amorphous thin films (T g = 88−127 °C) with a high decomposition temperature, T dec > 450 °C. Remarkably, undoped OF(2)Ar-NPh-based multilayer OLEDs could exhibit good to excellent device performance with emission colors spanning the full UV−vis spectrum. OF(2)Ar-NPh bearing oligothiophene core based devices exhibit a maximum luminance of 5000−12500 cd m-2 and luminous efficiency up to 3.6−4.0 cd A-1. Our findings provide a practical approach to design and tune the color emission of efficient and potentially useful light emitting materials.

Scanning tunneling microscopy of the formation, transformation, and property of oligothiophene self-organizations on graphite and gold surfaces

“…For example, the transistors fabricated with thiophene derivatives shows high charge-carrier mobility, high on/off modulation ratio, and long life (15). By modifying molecular structures with functional groups, alkyl chains and thiophene rings, the emitting color of an OLED can be regulated from blue to red (17).…”

Synthesis and fluorescence emission properties of 1,3,6,8-tetraarylpyrenes

“…The C9 site of the fluorene molecule can be easily functionalized, which provides for the possibility of improved solubility and processability, and of controlling the excimer formation in the excited state [22][23][24]. Recently, fluorene-based compounds have been extensively used as thermally stable and efficient emissive OLED materials [2529] and as high carrier transport organic field-effect transistors (OFETs) material [30][31][32].…”

Fluorene-Based Conjugated Oligomers for Organic Photonics and Electronics

“…Thiophenes, bithiophenes [68], dibenzothiophene [69], and longer oligothiophene segments have all been incorporated [70]. Some additional examples are shown in Fig.…”

“…Benzothiadiazole is a useful green emitter and electron-deficient moiety [64], and can also give rise to red emission when connected to fluorene via phenylene-vinylene segments, as in compound 29. Thiophene-S,S-dioxide and dibenzothiophene-S,S-dioxide are other electrondeficient co-monomers [69,80,81] used with fluorene.…”

“…The photoluminescent quantum yield in solution can be as high as 75 to 82% from the sky blue to the orange with a slightly lower efficiency in the red at 47% [64]. A number of fluorene co-oligomers have emission at wavelengths across the visible spectrum, from sky-blue [72-74, 95, 146-149] to green [67,98,124,150,151], yellow [72] and red [69,90,152]. Attached as ligands to iridium, oligofluorenylpyridines are capable of red phosphorescence with emission efficiencies up to 24% [153].…”