Crystal to crystal phase transition in alfa quaterthiophene: an optical and structural study

At 191 °C the organic semiconductor -quaterthiophene is demonstrated to undergo a phase transition from the low temperature to the high temperature polymorph. Calorimetry, x-ray diffraction, optical reflectivity, and ellipsometry measurements were employed to analyze this transition and to show that this can be thermally induced on single crystals preserving the single crystalline nature of the sample over large domains.