Organic devices have shown great promise during the past decade. These devices have several advantages including light weight, flexibility, ease of manufacturability and low cost. These pros make the organic devices good candidates to replace the current semiconductor technology in the areas of thin film transistors, photovoltaics and light-emitting diode fabrication. Pentacene as a conjugated compound shows high performance (including high carrier mobility) among many organic compounds. In contrast to the high electrical performance, these materials suffer from photo-oxidation, a phenomenon in which the devices degrade over time. In this research novel derivatives of pentacene are introduced and electrically characterized. All these materials are photo-oxidation resistant. The photo-oxidation resistance of these compounds varies as a function of the substituent. æThe electrical behavior of the transistors made out of a few derivatives is similar to that of conventional transistors. The electrical characteristics of a few other compounds are suppressed by the contact.