Luminescence probing of crystallization in a polymer film

We report studies of a thin film multilayer stack including a highly emissi ve substituted polythiophene, poly[3-(2,5-dioctylphenyl)thiophene]. Analysi s of the photoluminescence spectra revealed an inhomogeneous polymer film. X-ray diffraction studies attribute the existence of an inhomogeneous film as originating from crystallization of the polymer. We used the interferenc e effect of light to detect the region of crystallization in the film. Phot oluminescence and absorption were redshifted upon crystallization and displ ayed an enhanced vibronic structure. Comparison between calculated and meas ured photoluminescence shows that the crystallization starts from the top o f the film and not from the supporting substrate. (C) 2000 American Institu te of Physics. [S0021- 8979(00)08112-3].