Stable All-Organic Radicals with Ambipolar Charge Transport.

A series of neutral long-lived purely organic radicals based on the stable [4-(N-carbazolyl)-2,6-dichlorophenyl]bis(2,4,6-trichlorophenyl)methyl radical adduct (Cbz-TTM) is reported herein. All compounds exhibit ambipolar charge-transport properties under ambient conditions owing to their radical character. High electron and hole mobilities up to 10-2 and 10-3  cm2 V-1 s-1 , respectively, were achieved. Xerographic single-layered photoreceptors were fabricated from the radicals studied herein, exhibiting good xerographic photosensitivity across the visible spectrum.

1,3-diphenylethenylcarbazolyl-based monomer for cross-linked hole transporting layers.

A new cross-linkable monomer containing 1,3-diphenylethenylcarbazolyl-based hole-transporting moieties and four reactive epoxy groups, was prepared by a multistep synthesis route from 1,3-bis(2,2-diphenylethenyl)-9H-carbazol-2-ol and its application for the in situ formation of cross-linked hole transporting layers was investigated. A high concentration of flexible aliphatic epoxy chains ensures good solubility and makes this compound an attractive cross-linking agent. The synthesized compounds were characterized by various techniques, including differential scanning calorimetry, xerographic time of flight, and electron photoemission in air methods.

Phenylethenyl-substituted triphenylamines: efficient, easily obtainable, and inexpensive hole-transporting materials.

Star-shaped charge-transporting materials with a triphenylamine (TPA) core and various phenylethenyl side arm(s) were obtained in a one-step synthetic procedure from commercially available and relatively inexpensive starting materials. Crystallinity, glass-transition temperature, size of the π-conjugated system, energy levels, and the way molecules pack in the solid state can be significantly influenced by variation of the structure of these side arm(s). An increase in the number of phenylethenyl side arms was found to hinder intramolecular motions of the TPA core, and thereby provide significant enhancement of the fluorescence quantum yield of the TPA derivatives in solution. On the other hand, a larger number of side arms facilitated exciton migration through the dense side-arm network formed in the solid state and, thus, considerably reduces fluorescence efficiency by migration-assisted nonradiative relaxation. This dense network enables charges to move more rapidly through the hole-transport material layer, which results in very good charge drift mobility (µ up to 0.017 cm(2) V (-1) s(-1)).

Air-stable, narrow-band-gap ambipolar C60 fullerene-hydrazone hybrid materials.

Fullerene-hydrazone dyads have been synthesized using the Confalone reaction followed by condensation with phenylhydrazines. Room-temperature xerographic time-of-flight, ionization potential, and cyclic voltammetry measurements indicate that these narrow-band-gap (E(g)<1.5 eV), ambipolar charge-transporting dyads with balanced hole- and electron mobilities, which operate in air, are attractive materials for various optoelectronic applications.

One small step in synthesis, a big leap in charge mobility: diphenylethenyl substituted triphenylamines.

Star-shaped charge transporting materials with a triphenylamine core and a varying number of diphenylethenyl sidearms, obtained using a one step synthesis procedure from commercially available and relatively inexpensive starting materials and possessing comparatively high hole drift mobility (up to 0.017 cm(2) V(-1) s(-1)), are reported.

Stable radical cores: a key for bipolar charge transport in glass forming carbazole and indole derivatives.

Stable radical adducts of the TTM series bearing carbazolyl or indolyl fragments show bipolar transport properties with mobility values among the highest detected in glassy small molecules. Bipolarity is attributed to the radical character, while the heterocyclic ring confers the adducts the glassy morphological states and the non-dispersive regimes for charge transport.