Theoretical and experimental studies on photophysical characteristics of low bandgap polymers

The basic photophysical characteristics of low bandgap polymer poly{2,7′-9,9-dioctylfluorene-alt-5-diethylhexyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione}(PDPP-F) have been systematically investigated by means of theoretical and experimental methods. The quantum chemical calculations clarify the molecular structure and electronic transition properties of PDPP-F. The transient absorption data were used to compare the relaxation dynamics of PDPP-F in chlorobenzene and solid film. It is observed that the dynamics process of simulated emission relaxes much faster in comparison with that of excited state absorption in both the solution and solid film. Moreover, the excitation intensity-dependent dynamics of PDPP-F confirms that the interaction among intrachain excitons may occur under photoexcitation in the solution and solid film.