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

A series of carbazole-based dyes functionalized with different auxochromes via vinyl linker have been synthesized and characterized. A progressive shift in the absorption maximum is observed as the conjugation and electron-donating nature of chromophore increases. Dyes containing electron-releasing terminal groups such as triphenylamine and carbazole exhibited positive emission solvatochromism attributable to an induced intramolecular charge transfer from triphenylamine/carbazole donor to cyano acceptor. The superior electroluminescence performance of disubstituted dyes demonstrates the role of an additional cyanocarbazole in achieving balanced charge transport compared to monosubstituted analogues. In addition, the electroluminescence performance of the dyes exhibited trends attributable to the electron richness of the linker/terminal chromophore. Thus, the carbazole-based derivatives displayed better electroluminescence efficiency than the analogous fluorene derivatives. Similarly, 2,7-substituted carbazole derivative exhibited better performance than the 3,6-substituted carbazole derivative. A doped electroluminescent device containing 3 wt % tricarbazole derivative showed blue emission with a high external quantum efficiency of 5.3% at a practical brightness of 1000 cd/m².

Multicolor Luminescence Switching and Controllable Thermally Activated Delayed Fluorescence Turn on/Turn off in Carbazole-Quinoxaline-Carbazole Triads

We report a series of thermally activated delayed fluorescence (TADF) molecules with mechanochromic luminescence properties and reversible TADF turn on/off properties in solid state that are induced by the transition between amorphous and crystalline states. Additionally, multicolor altering through external stimulus is demonstrated. All of the studied compounds exhibited recovery of the initial states associated with narrower emission spectra. TADF organic light-emitting diodes fabricated by solution processing rendered high external quantum efficiency up to 10.9% and luminance of 16 760 cd m^-2.

The synthesis of lactone-bridged 1,3,5-triphenylbenzene derivatives as pi-expanded coumarin triskelions

Two triply lactone-bridged 1,3,5-triphenylbenzene derivatives with solubilizing moieties have been synthesized in five and six steps from commercially available starting materials. Compounds containing the 1,3,5-triphenylbenzene core with two atom bridges are relatively unknown. This new class of pi-expanded coumarins contain triskelion architectures and X-ray crystallographic studies of one of the triskelions indicates that the 1,3,5-triphenylbenzene core adopts a near-planar geometry. This is the only known example of a two atom-bridged 1,3,5-triphenylbenzene derivative to adopt a planar structure.

Carbazole- and/or triphenylamine-based D–π–D multiarylamino dyes: synthesis, characterization and photophysical properties

One-photon and two-photon fluorescence quenching by benzoyl peroxide of D–π–D multiarylamino dyes was investigated.

Tuning the ambipolar charge transport properties of tricyanovinyl-substituted carbazole-based materials

The ambipolar charge transport properties of a series of push–pull carbazole-based semiconductors are here evaluated. The ambipolar characteristics depend on the supramolecular organization. Experimental results were confirmed and justified through the X-ray analysis of single crystals and by theoretical calculations.

3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic-organic hybrid perovskite solar cells

The ever increasing demand for clean energy has encouraged researchers to intensively investigate environmentally friendly photovoltaic devices. Inorganic-organic hybrid perovskite solar cells (PSCs) are very promising due to their potentials of easy fabrication processes and high power conversion efficiencies (PCEs). Designing hole-transporting materials (HTMs) is one of the key factors in achieving the high PCEs of PSCs. We now report the synthesis of two types of carbazole-based polymers, namely 3,6-Cbz-EDOT and 2,7-Cbz-EDOT, by Stille polycondensation. Despite the same chemical composition, 3,6-Cbz-EDOT and 2,7-Cbz-EDOT displayed different optical and electrochemical properties due to the different connectivity mode of the carbazole unit. Therefore, their performances as hole-transporting polymeric materials in the PSCs were also different. The device based on 2,7-Cbz-EDOT showed better photovoltaic properties with the PCE of 4.47% than that based on 3,6-Cbz-EDOT. This could be due to its more suitable highest occupied molecular orbital (HOMO) level and higher hole mobility.

New solution-processable carbazole derivatives as deep blue emitters for organic light-emitting diodes

Triple bonds as π-spacers in deep blue carbazole-based emitters for non-doped organic light-emitting diodes.

Green and red phosphorescent organic light-emitting diodes with ambipolar hosts based on phenothiazine and carbazole moieties: photoelectrical properties, morphology and efficiency

The two low-molar mass compounds based on phenothiazine and carbazole moieties were synthesized and investigated as the ambipolar hosts for the green and red phosphorescent organic light emitting diodes.