Novel organic materials that permanently increase conductivity upon thermal or photo treatment

In this work, we tested an approach towards novel organic materials that can permanently increase conductivity upon thermal or photo treatment, and potentially, change from insulator to conductor or semiconductor. Using dichlorodicyanoquinone (DDQ) doped thermo and photo responsive pentacene precursors as model systems, we found that conductivity of the thermal responsive material increased over 2 orders of magnitude to 10−3–10−2 S/cm after thermal treatment, while that of a photo responsive material did not significantly increase after photo irradiation even though the composites are same. Based on the results of conductivity measurement, SEM, XRD, UV–Vis, and FT–IR, the phenomena are attributed to that the crystalline morphology of thermally generated pentacene/DDQ thin films favored charge transfer while the amorphous morphology of the photo generated material favored solid-state Diels–Alder reaction. The result implies that the mechanism of solid-state reaction can be altered by controlling morphology.