Novel Bifunctional Molecule for Photorefractive Materials

We report on the synthesis and characterization of a novel photorefractive polymer composite that consists of a bifunctional molecule based on the charge-transport molecule N,N ‘-diphenyl- N,N ‘-bis(3-methylphenyl)-[1,1‘-biphenyl]-4,4‘-diamine (TPD). It is shown that the low values obtained for the gain coefficient and the diffraction efficiency (10 cm - 1 and 0.1%, respectively) are a result of the low intrinsic trap density. The gain coefficient and the diffraction efficiency are dramatically increased to 6% and 45 cm - 1, respectively, by adding only small amounts of the molecule N,N,N ‘, N ‘- tetramethyl-4-phenylene diamine (TMPD), which is shown to cause an increase in the trap density. The behavior of the diffraction efficiency, gain coefficient, response time, and phase shift upon the concentration of TMPD are discussed within the standard model of photorefractivity.