Solution-processable hole-transporting material containing fluorenyl core and triple-carbazolyl terminals: synthesis and application to enhancement of electroluminescence

Abstract

A novel solution-processable, efficient hole-transporting material 2,4,7-tri[2-(9-hexylcarbazole)ethenyl]-9,9-dihexylfluorene (FC), composed of a fluorenyl core and triple-carbazolyl terminals, is successfully synthesized and well characterized. The FC is a thermally stable, amorphous material because of its aromatic and asymmetric structure. The highest occupied molecular orbital (HOMO) level of FC is -5.21 eV, as determined by cyclic voltammetry, implying its applicability as a hole-transporting layer (HTL) to promote hole injection. Furthermore, the FC could be deposited by a spin-coating process to obtain a homogeneous HTL film, more convenient and cost-effective than conventional NPB which must be deposited by vacuum vapor deposition. When fabricated as multi-layer OLED [ITO/PEDOT:PSS/HTL(25 nm)/Alq3(50 nm)/LiF(0.5 nm)/Al(100 nm)], the maximum brightness (21,400 cd m(-2)) and current efficiency (3.20 cd A(-1)) based on the FC are superior to those using conventional NPB as the hole-transporting layer. In addition, a homogeneous FC film is readily prepared by simple wet processes (spin-coating). Our results indicate that the FC is a promising optoelectronic material which is readily processed by wet methods such as spin-coating.

A Novel trans‐1‐(9‐Anthryl)‐2‐phenylethene Derivative Containing a Phenanthroimidazole Unit for Application in Organic Light‐Emitting Diodes

“…The absorption bands at approximately λ =300–400 nm can be associated with the π–π* transitions of the t ‐APE and PPI moieties . No clear redshift in the absorption bands in the film state suggests that no significant crystallization occurs in the film . In THF solution, APE‐PPI exhibits a maximum PL (PL max ) value at a blue–green wavelength of 486 nm and a full width at half maximum (FWHM) value 82 nm.…”

Effect of the length of the alkyl chains in porphyrin meso-substituents on the performance of dye-sensitized solar cells

“…[41][42][43][44] Compounds 2a-2c were prepared by the Vilsmeier-Haack reaction according to procedures reported in literature. [45][46][47] Compound 2a. POCl 3 (3.69 g, 24 mmol) was added very slowly to dry DMF (2.2 g, 30 mmol) at 0 C within 4 hours.…”

Vinyl-Linked Cyanocarbazole-Based Emitters: Effect of Conjugation and Terminal Chromophores on the Photophysical and Electroluminescent Properties

“…20,21 Carbazole derivatives containing vinyl linker at C3- and N9-positions are known for their hole-transporting character, which is comparable to that of the widely used hole transporter, N , N ′-bis(naphthalen-1-yl)- N , N ′-bis(phenyl)benzidine. 22,23 Carbazole, tethered naphthalene via vinyl linker, showed green emission with good quantum yield, yet the device performance was not up to the mark due to the imbalanced charge transport. 24,25 Further, carbazole and anthracene conjugates possessing vinyl spacer are demonstrated as aggregation-induced emitters.…”