Photoinduced Polarons and Exciton in Polythiophene Films

Absorption and luminescence induced by a photoexeitation are studied in polythiophene and poly(3-methylthiophene) films. The photoinduced absorption spectra which are nearly consistent with those of dopant-induced absorption at dilute doping levels indicate that the dominant photo induced charged species are polarons. It is found that the magnitude of photoinduced absorption is rather independent on the condition of sample preparation, whereas the photoluminecence intensity is strongly influenced. The result suggests that the luminescent exciton does not play aprimary role in the photogeneration of polaronic species.