Linear and nonlinear photoexcitation dynamics in π-conjugated polymers

(Received 21 July 2002; published 28 January 2003)Linear and nonlinear recombination kinetics with various lifetime distributions were identified forlong-lived photoexcitations in a series of -conjugated polymer films using modulation frequency andexcitation intensity dependencies of the photoinduced absorption. This includes monomolecular,bimolecular, and defect-limited recombination processes that lead to saturation. Using generalizedkinetics parameters, we found characteristic plots for all recombination processes. Specifically, thebimolecular recombination process shows superlinear intensity dependence away from the steady state;on the contrary, dispersive bimolecular recombination leads to sublinear dependence.