%0 Journal Article %1 C6CP01780K %A Hader, Kilian %A May, Volkhard %A Lambert, Christoph %A Engel, Volker %D 2016 %I The Royal Society of Chemistry %J Phys. Chem. Chem. Phys. %K ak-engel %N 19 %P 13368-13374 %R 10.1039/C6CP01780K %T Identification of effective exciton-exciton annihilation in squaraine-squaraine copolymers %U http://dx.doi.org/10.1039/C6CP01780K %V 18 %X Ultrafast time-resolved transient absorption spectroscopy is able to monitor the fate of the excited state population in molecular aggregates or polymers. Due to many competing decay processes, the identification of exciton-exciton annihilation (EEA) is difficult. Here, we use a microscopic model to describe exciton annihilation processes in squaraine-squaraine copolymers. Transient absorption time traces measured at different laser powers exhibit an unusual time-dependence. The analysis points towards dynamics taking place on three time-scales. Immediately after laser-excitation a localization of excitons takes place within the femtosecond time-regime. This is followed by exciton-exciton annihilation which is responsible for a fast decay of the exciton population. At later times, excitations being localized on units which are not directly connected remain so that diffusion dominates the dynamics and leads to a slower decay. We thus provide evidence for EEA tracked by time-resolved spectroscopy which has not been reported that clearly before.

@article{C6CP01780K, abstract = {Ultrafast time-resolved transient absorption spectroscopy is able to monitor the fate of the excited state population in molecular aggregates or polymers. Due to many competing decay processes{,} the identification of exciton-exciton annihilation (EEA) is difficult. Here{,} we use a microscopic model to describe exciton annihilation processes in squaraine-squaraine copolymers. Transient absorption time traces measured at different laser powers exhibit an unusual time-dependence. The analysis points towards dynamics taking place on three time-scales. Immediately after laser-excitation a localization of excitons takes place within the femtosecond time-regime. This is followed by exciton-exciton annihilation which is responsible for a fast decay of the exciton population. At later times{,} excitations being localized on units which are not directly connected remain so that diffusion dominates the dynamics and leads to a slower decay. We thus provide evidence for EEA tracked by time-resolved spectroscopy which has not been reported that clearly before.}, added-at = {2017-06-20T16:32:41.000+0200}, author = {Hader, Kilian and May, Volkhard and Lambert, Christoph and Engel, Volker}, biburl = {https://www.bibsonomy.org/bibtex/2661ea30977875a10d3e69f04297e0c87/ak-engel-uniwue}, description = {Identification of effective exciton–exciton annihilation in squaraine–squaraine copolymers - Physical Chemistry Chemical Physics (RSC Publishing)}, doi = {10.1039/C6CP01780K}, interhash = {9d72e1349dd4da9153879c94fc0c8f81}, intrahash = {661ea30977875a10d3e69f04297e0c87}, journal = {Phys. Chem. Chem. Phys.}, keywords = {ak-engel}, number = 19, pages = {13368-13374}, publisher = {The Royal Society of Chemistry}, timestamp = {2017-06-20T16:32:41.000+0200}, title = {Identification of effective exciton-exciton annihilation in squaraine-squaraine copolymers}, url = {http://dx.doi.org/10.1039/C6CP01780K}, volume = 18, year = 2016 }