Controlling the spatial location of photoexcited electrons in semiconductor CdSe/CdS core/shell nanorods
Chunxing She, Garnett W. Bryant, Arnaud Demorti?, Elena V. Shevchenko, Matthew Pelton
It is commonly assumed that, after an electron-hole pair is created in a semiconductor by absorption of a photon, the electron and hole rapidly relax to their respective lowest-energy states before recombining with one another. In semiconductor heterostructure nanocrystals, however, intraband relaxation can be inhibited to the point where recombination occurs primarily from an excited state. We demonstrate this using time-resolved optical measurements for CdSe/CdS core/shell nanorods. For nanorods with large CdSe cores, an electron photoexcited into the lowest-energy state in the core remains in the core, and an electron photoexcited into an excited state in the CdS shell remains in the shell, until the electron recombines with the hole.