9-(2-Ethylhexyl)carbazole for carrier transport and photorefractive materials

We investigated the carrier transport and photorefractive properties in multi-component materials containing 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole. The electric-field dependence of the carrier mobility for EHCz and polyvinylcarbazole (PVK) was measured by the time-of-flight (TOP) technique. We obtained the higher carrier mobility of 4.2×10 ^-6 cm ² /Vs with an electric field of 2.5×10 ⁵ V/cm for EHCz than that of 6.4×10 ^-7 cm ² /Vs for PVK. We also performed the two-beam coupling (TBC) technique to investigate photorefractive responses for the guest-host polymers containing PVK, EHCz, the electro-optic chromophore 4-piperidinobenzylidene malonitrile (PDCST), and the sensitizer C ₆₀ . The measurement showed that the TBC gain depended on the mixture ratio of PVK and EHCz. The TBC gain was enhanced from 31 to 85 cm ^-1 at an electric field of 60 V/μm by increasing the concentration of EHCz from 10 to 15 wt%. These results show that EHCz plays important role for the optoelectronic and photorefractive materials as a hole transport materials as well as a plasticizer.