Layer-Structured Photoconducting Polymers: A New Class of Photorefractive Materials


  • This work was supported in part by the Korea Research Foundation Grant (KRF-2000-015-DP0172).


We study the photorefractive (PR) properties of a new kind of low glass-transition temperature (Tg) polymer composite based on layered photoconductive polymers, poly(p-phenylene terephthalate) carbazoles (PPT-CZs). These photoconductors consist of the rigid backbone of PPT with pendant oxyalkyl CZ groups. The compounds are doped with the photosensitizer C60 and nonlinear optical chromophores diethylaminodicyanostyrene (DDCST), and no plasticizers are added. When the host polymers are mixed with various PR ingredients, the layers are preserved and their layer distance increases, indicating that all the guest molecules are confined to the nanoscale interlayer space. These composites showed very low Tg values (< ϕ °C). Despite the absence of a plasticizer and the lower concentration of the carbazole photoconductive moieties as compared to poly(N-vinylcarbazole) systems, these materials show excellent PR properties, i.e., a PR gain of Γ = 250 cm–1 under an external electric field of 60 V μm–1, and diffraction efficiency and PR sensitivity of 93 % and 24 ± 7 cm2 kJ–1 at E = 100 V μm–1, respectively.