Photorefractivity in a polymeric composite photosensitized with NiS nanocrystals.

The photorefractive performance of a polymeric composite photosensitized through the inclusion of NiS nanocrystals is described. The nanocrystals were characterized using visible-absorption spectroscopy, energy-dispersive x-ray spectroscopy, and transmission electron microscopy. We further demonstrate the ability to enhance various aspects of the composite's photorefractive performance by performing ligand exchange on the nanocrystals prior to their incorporation into the polymer composite. This procedure resulted in a lowering of the overmodulation voltage from approximately 70 to approximately 50 V/microm without affecting the maximum diffraction efficiency of approximately 40%. An increase in the two-beam-coupling gain coefficient was similarly observed, increasing from 38 to 79 cm(-1). The photoconductivities were used in determining the overall quantum efficiencies associated with the photorefractive devices. All experiments were conducted at 633 nm and the data represent a significant improvement in the photorefractive performance of inorganic-organic hybrid photorefractive materials.