Ionic conduction in sol-gel overcoats for organic photoreceptors

Silsesquioxanes are a class of silicone polymers that are useful as abrasio n resistant overcoats for organic photoreceptors. We have manipulated the e lectrical properties of this sol-gel matrix by incorporating a solid electr olyte. Solid electrolytes, also referred to as solid ionic conductors, are materials in which electrical conductivity is provided by the motion of ion s. We chose (3-glycidoxypropyl)trimethoxysilane (GPS) as the most suitable commercially available monomer to form the polymer matrix for lithium iodid e migration. This epoxysilane contains two ether oxygen atoms for coordinat ion to low lattice energy salts. A good correlation was observed between th e level of GPS and the electrical properties of the coating, with increasin g concentration of GPS in the silsesquioxane resulting in decreased resisti vity. The silsesquioxane is a hard material and the resistivity remained re latively high, between 10(10)-10(13) ohm-cm. However, this is a desirable r esistivity for maintaining image quality with an overcoated photoreceptor.