Abstract
Exciton migration and annihilation dynamics in J aggregates comprised of a pseudoisocyanine (PIC) dye and poly(vinyl sulfate) (PVS) are studied by time-correlated, single-photon-counting (TCSPC) methods coupled with near-field scanning optical microscopy (TCSPC-NSOM) and also by conventional, far-field TCSPC. Far-field TCSPC studies of the aggregates in aqueous solution demonstrate that the exciton lifetime in the absence of annihilation (at low excitation intensities) is 789 ± 36 ps with biexponential exciton decay occurring at high excitation intensities due to exciton annihilation. Analysis of the intensity-dependent decay with conventional exciton decay theories demonstrates that the observed decay dynamics are consistent with exciton migration limited to finite molecular domains. In contrast to the solution studies, deposition of a thin PIC/PVS aggregate film onto fused quartz results in a dramatic reduction in the exciton lifetime to ∼10 ps. This lifetime demonstrates only modest dependence on excit...
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