Exciton Migration and Surface Trapping for a Photonic Crystal Displaying Charge-Recombination Fluorescence.
A compact donor-acceptor molecular dyad has been synthesized by attaching an N,N-dimethylamino fragment to a naphthalic anhydride residue. The dyad shows fluorescence from an intramolecular charge-transfer state (i.e., charge-recombination fluorescence) in solution, with the photo-physical properties being strongly dependent on the solvent polarity. Similar emission is seen for single crystals of the target compound, the molecules being aligned head-to-head, although time-resolved emission profiles display dual-exponential kinetics. A second polymorph with the head-to-tail alignment also gives rise to two lifetimes that differ somewhat from those of the first structure, which are assigned to bulk and surface-bound molecules. Growing the crystal in the presence of Rhodamine B localizes the dye around the surface. Excitation of the crystal is followed by sub-ps exciton migration along the aligned stacks, with occasional crossing to adjacent stacks and trapping at the surface. Rhodamine B present at very low levels acts as the acceptor for excitons entering the surface layer. Crystals embedded in a polyester resin form an artificial light-harvesting antenna able to sensitize an amorphous silicon solar cell.
Molecular Photonics Laboratory, School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
Roza
R
Al-Aqar
Molecular Photonics Laboratory, School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.|Department of Polymer Engineering, Faculty of Technology, Duzce University, Duzce, 81620, Turkey.
Alparslan
A
Atahan
Molecular Photonics Laboratory, School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
Andrew C
AC
Benniston
Molecular Photonics Laboratory, School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
Thomas
T
Perks
Crystallography Laboratory, School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
Paul G
PG
Waddell
Molecular Photonics Laboratory, School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. anthony.harriman@ncl.ac.uk.
Anthony
http://orcid.org/0000-0003-0679-2232
A
Harriman
electronic energy transfer; fluorescence; light harvesting; photophysics; polymorph