Carbazole-containing polymers: synthesis, properties and applications

Summary: Carbazole-based oligomeric and polymeric materials have been studied for almost 25 years for their unique electrical, electrochemical and optical properties. Interestingly, carbazole units can be linked in two different ways leading to either poly(3,6-carbazole) or poly(2,7-carbazole) derivatives. While the former class seems to be very interesting for electrochemical and phosphorescence applications, the latter shows very promising optical properties in the visible range for light emitting diodes (LED). The major intrinsic difference between these two classes is the effective conjugation length: poly(2,7-carbazole) materials having the longer one, due to their poly(p-phenylene)-like structure. Using different synthetic strategies and substitution patterns, the physico-chemical properties of both classes can be fine-tuned, leading to high performance materials for a large number electronic applications.

Chemical structures for poly(3,6-carbazole) and poly(2,7-carbazole) and the materials used as the starting points for their respective syntheses.

Polycarbazoles: 25 Years of Progress

Porphyrins and phthalocyanines as materials for optical limiting

Xerographic photoreceptors charge acceptance and dark discharge photoinduced discharge photogeneration theories photogeneration in organic solids charge transport theories charge transport in polymers and related materials experimental techniques photoreceptor preparation photoreceptors fatigue summary and future requirements.

Organic Photoreceptors for Imaging Systems

The combination of scanning tunneling microscopy (STM) with optical excitation adds new information to STM. A review is presented covering the work done on light-induced effects in STM during the past 15 years. Effects discussed include thermal effects, nonlinear effects, field enhancement at the STM tip, various effects on semiconductor surfaces, excitation of surface plasmons, detection of photoelectrons, spin-polarized tunneling, as well as light-induced nanomodifications, local optical spectroscopy, the use of ultrashort laser pulses for time-resolved STM, and the combination of STM and scanning near-field optical microscopy.

Photoassisted scanning tunneling microscopy

Charge transport properties in liquid carbazole

Acceptor-substituted carbazole derivatives were newly designed as novel nonlinear optical materials with photoconductive properties Various 3-, 6- and 9-substituted carbazole derivatives were synthesized systematically and their optical second-harmonic generation (SHG) activity and crystallographic structures were examined Enhancement of molecular hyperpolarizability ( beta ) was achieved and an intracharge-transfer band was observed by introducing electron-withdrawing groups in 3 and/or 6 positions The hydrogen bonding in the 9-hydroxyethyl substituent plays an important role in generating non-centrosymmetric packing of carbazole molecules Single crystals of 9-hydroxyethylcarbazole (HEK), 3-nitro-9-hydroxyethylcarbazole (NHEK) and 3,6-dinitro-9-hydroxyethylcarbazole (DNHEX) can be obtained by the solution growth technique The HEK and NHEK crystals were determined to have non-centrosymmetric crystallographic structures with tetragonal and monoclinic unit cells These crystals have unique space groups I41 and P21, and hydrogen bonding was formed in adjacent hydroxy groups In these crystals each carbazole ring is aligned along the same direction On the other hand, DNHEK has a centrosymmetric unit cell with space group P1 In this case the hydrogen bond involves a hydrogen on a hydroxy oxygen interacting with the nitro oxygen in an adjacent molecule The highly aligned carbazole system is attractive in terms of structure related properties such as the carrier transport process and second-order nonlinear optical responses

http://iopscience.iop.org/article/10.1088/0022-3727/26/8B/037/pdf

Photoconductive crystals for nonlinear optics: molecular design and crystal structure

Nanoscopic studies investigated by hybrid SNOM/STM

Nonlinear optically active compounds newly designed and synthesized in Frontier
Research Program were reviewed: single crystal of dicyanovinyl anisole (DIVA) for
blue light generation, one- or two-dimensional r -conjugated systems such as polythiophenes,
polydiynes, soluble phthalocyanines and annulenes, for third order
optical nonhinearities and waveguide application. As a promising technique to control
the molecular orientation and assembly, the organic molecular beam epitaxy (OMBE) is
proposed.

Photonics and organic nanostructures

The emission properties of cyclic carbazole oligomers are described. The photoluminescent spectra of these cyclic oligomers excited by 350 nm as an excitation wavelength in chloroform have been measured. We found that
 the emission properties of o-xylene-derived cyclic dimer were different from those of p- and/or m-xylene-derived cyclic dimers although they have the similar molar absorption
 coefficients
 and structures.
 The electroluminescent properties are also described.

Tatsuo Wada

Papers

Charge transport properties in liquid carbazole

Photoconductive crystals for nonlinear optics: molecular design and crystal structure

Nanoscopic studies investigated by hybrid SNOM/STM

Photonics and organic nanostructures

The photoluminescent and electroluminescent properties of cyclic carbazole oligomers