Charge Carrier Transport Properties in Polymer Liquid Crystals Containing Oxadiazole and Amine Moieties in the Same Side Chain

Abstract

Steady-state and transient photocurrent measurements were carried out to study the charge carrier transport properties of polymer liquid crystal (LC) containing oxadiazole (OXD) and amine moieties in the same side chain. The steady-state photocurrent measurement with asymmetric electrodes of ITO and Al and a short penetration depth of the illumination light indicated that both electrons and holes can be transported in this film. The transient hole photocurrent observed by time-of-flight (TOF) experiments was dispersive at room temperature. The hole drift mobility significantly depended on temperature and electric field and was determined to be 6.1 x 10(-8) cm2/Vs at a field of 9.1 x 10(5) V/cm. According to the disorder formalism, the Gaussian width of the density of states was determined to be 170 meV for holes. Despite the indication of possible electron transport in this film, we could not determine the electron mobility by TOF experiments due to strong dispersive photocurrent. We discuss the present charge transport properties of the film in relation to a large dipole attributed to an electrical push-pull structure of p-dimethylaminophenyl-substitited OXD moiety in polymer LC and its electroluminescent properties.

A novel mesogen‐jacketed liquid crystalline electroluminescent polymer with both thiophene and oxadiazole in conjugated side chain

“…Similar considerations of introducing self‐organized structures such as liquid‐crystalline polymers have also been reported, and the improvement of the EL properties was ascribed to the bipolar carrier‐transporting abilities of the LC molecules 30, 31. Moreover, high ordered phase structure was expected to replace N phase to facilitate the charge carrier transport,32 which was realized in this investigation.…”

1,3,4-Oxadiazole based liquid crystals

“…The hole dri mobility of 71a in lm was estimated to be 6.1 Â 10 À8 cm 2 V À1 s À1 in an applied eld of 9.1 Â 10 5 V cm À1 , which was dispersive and signicantly dependent on temperature and electric eld due to the low ordered nematic phase of the polymer. 121 Recently, the same group further fabricated phosphorescent light-emitting diodes (PLEDs) with polymer 71b as the host material, and found that the PLEDs using the liquid crystalline polymer displayed a higher luminance efficiency than those using an amorphous polymer. 122 6.3.…”

Preparation and properties of electron injecting molecular hybrid materials with high thermal performance

“…1 For overcoming this problem, many oxadiazole-containing derivatives such as organic starlike materials and polymers with oxadiazole as a pendant group have been developed. [7][8][9][10][11][12] For example, Yeh et al demonstrated that a rigid tetrahedral molecular skeleton is effective for improving thermal stability and a stable amorphous phase of either molecular or oligomeric oxadiazole materials. 4 Cha et al synthesized anthracene cored four-armed oxadiazole compounds with high glass transition temperature.…”