(The) photorefractive effect of CNT-doped PVK layers in a PR-LC cell

Abstract

The Poly(9-vinylcarbazole) (PVK) layers doped with carbon nanotubes were fabricated to investigate the photorefractive effects such as two beam coupling ratio, 1st order Raman-Nath diffraction efficiency and grating formation time. Single wall carbon nanotubues (SWNTs) and multi wall carbon nanotubes (MWNTs) were successfully purified and cut by chemical treatment and dispersed with didecylamine (DDA). Several kinds of carbon nanotubes (CNTs) were made; purified SWNTs and MWNTs (not cut), cut SWNTs (not centrifuged and centrifuged) and MWNTs (not centrifuged) and DDA modified SWNTs (SDDA) and MWNTs (MDDA). All of these CNTs were characterized in terms of the degree of purity, length, damage and surface modification of CNTs. PR-LC cells were classified by the % ratio of CNTs to PVK; 0.03 to 99.97, 0.05 to 99.95, 0.07 to 99.93 and 0.09 to 99.91 respectively. All cells showed the PR effect of enhanced beam coupling ratio, 1st order Raman-Nath efficiency over the threshold DC field, but decreased after the optimum DC field. Among the tested cells, the optimum % ratio of CNTs to PVK is found to be 0.05 to 99.95 in weight percentage. DDA showed a little effect by not only improving dispersion stability of CNTs in toluene, but also covering defects of treated CNTs with damaged surface. Especially, the length of CNTs was apparently believed to be the most important parameter in PVK layers.