Thursday, 04 January, 2007
Room-Temperature Exciton Storage in Elongated Semiconductor Nanocrystals
R.M. Kraus, P.G. Lagoudakis, A.L. Rogach, D.V. Talapin, H. Weller, J.M. Lupton and J. Feldmann -
Phys. Rev. Lett. 98, 017401 (2007)
The excited state of colloidal nanoheterostructures consisting of a spherical CdSe nanocrystal with an epitaxially attached CdS rod can be perturbed effectively by electric fields. Field-induced fluorescence quenching coincides with a conversion of the excited state species from the bright exciton to a metastable trapped state (dark exciton) characterized by a power-law luminescence decay. The conversion is reversible so that up to 10% of quenched excitons recombine radiatively post turn-off of a 1 µs field pulse, increasing the delayed luminescence by a factor of 80. Excitons can be stored for up to 105 times the natural lifetime, opening up applications in optical memory elements.