Light emission and amplification in charged CdSe quantum dots

Photoluminescence from charged colloidal CdSe quantum dots, with definite and controllable electron occupation, is observed. As charged nanocrystals still emit light but are transparent at the emission wavelength, the threshold for amplified stimulated emission is strongly reduced. We demonstrate 65% threshold reduction in charged CdSe nanocrystal films, and further reduction should be feasible. This opens new possibilities for achieving efficient lasing in these molecular-like systems.