Sol-gel derived oligosiloxane resins are cured under air or N-2 by a photo-initiated thiol-ene reaction. The cured film was fabricated as a dielectric layer for use in an organic thin film transistor, and offers a higher dielectric constant (4.13) than silicon dioxide (3.9). We investigated the effects of the curing conditions of a thiol-ene reaction on the TFT performance depending on air or N-2. In the N-2 conditions, hydroperoxide group (-OOH) free films were generated and they showed low leakage current density and hysteresis free behavior with higher mobility than those fabricated in air. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.021205esl] All rights reserved.