Photoinduced phase transformation in polythiophene

The thermally restorable photoswitching between the spectroscopically distinct two phases has been observed for thin films of poly(3-alkylthiophene) with regioregular alkyl sidegroups. The primary process of the photoinduced phase transition is completed within a duration of the exciting laser pulse (5 ns), in which photogenerated electron-hole pairs on the polymer backbone with the density above a critical value appear to trigger a self-activated process for the phase conversion. Such a fast photoswitching of the electronic and/or structural state may be applied as well to many other conjugated polymers with optoelectronic functionality.