Organic materials have been given much attention due to their intriguing properties that can be tailored via synthetic chemistry for specific applications combined with their low price and fairly straight-forward large-scale synthesis. Para-hexaphenylene (p6P) nanofibers emit polarized light with a highly anisotropic emission profile, act a sub-wavelength optical waveguides, and form the basis for a new type of miniature OLEDs. However, p6P molecules suffer reduction of luminescence intensity during photoexcitation under UV light. Such photoreaction is understood as a consequence of the interaction of the fibers with oxygen. We have developed a bilayer coating that does not change significantly the p6P spectrum but strongly reduces bleaching. This bilayer coating consists of a first layer of a stable polymer (PMMA) on top of the organic nanofibers as a protecting layer for avoiding modifications of the p6P luminescence spectrum and as a second layer SiOx for blocking the oxyg en penetration. In this work, we show the applicability of this bilayer coating of PMMA/SiOx in prolonging the operational lifetime of field-effect transistor (FET) devices based on p6P nanofibers. The coating prevents strong degradation of transferred nanofibers on FET platforms during electrical biasing as is observed for uncoated devices. We are currently investigating the effect of the coating during electrically stimulated light emission experiments from transferred fibers on transistor platforms.