Synthesis and unusual physical behavior of a photorefractive polymer containing tris(bipyridyl)ruthenium(II) complexes as a photosensitizer and exhibiting a low glass-transition temperature

This paper reports the synthesis and characterization of a low-T-g photorefractive (PR) polymer which contains ionic ruthenium complexes as the photogenerator of charge carriers. It was expected that a combination of the highly efficient photocharge generation of the Ru complex, the efficient charge transporting of the conjugated backbone, and the orientational enhancement associated with low-T-g materials would lead to further improvement of PR performances. However, it was very interesting to find that the PR performance of this polymer was Limited by the local internal field formed in response to the external electric field by the alignment of ion pairs around the photocharge generation sites. The effects of such a local field on photocharge generation and photorefractivity were investigated through the analyses of the dependence of photocurrent, photorefractive gain, diffraction efficiency, electrooptic activity, and birefringence on the applied field. The dynamic behavior of the PR grating formation was also investigated.