Triplet build in and decay of isolated polyspirobifluorene chains in dilute solution

The triplet kinetics of a conjugated polymer, polyspirobifluorene, have been studied using time resolved photoinduced absorption spectroscopy and gated emission delayed fluorescence. Working on isolated polymer chains in dilute solution, we pay particular attention to the buildup and decay of the triplet states following intersystem crossing from the excited singlet state. Confirmation of intersystem crossing as a monomolecular cold process has been made. At high excitation powers an initial fast decay of the triplet has been observed; this is attributed to intrachain triplet-triplet annihilation. From this observation we estimate the lower bound of the intersystem crossing yield as 1.2%. We also calculate the intrachain annihilation constant to be (2.9+/-0.1)x 10(8) cm(3) s(-1).