For the past three decades, the field of quantum dot research has been expanding enormously, owing to the unique dynamics of charge carriers in these tiny crystals. This review provides an overview of charge carrier dynamics in photoactivated quantum dots. Specifically, it deals with the exciton fine structure, multiple exciton generation and the origin and control of photoluminescence intermittency in cadmium and lead chalcogenide quantum dots. These properties are discussed within the framework of spectroscopy and microscopy of single and multiple exciton states. Finally, this review touches on the photoluminescence- and multiple exciton- based applications of quantum dots, such as lasing and high efficiency solar cells.

Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to the electromagnetic field, creating a new photon with a frequency, polarization, and direction of travel that are all identical to the photons of the incident wave. This is in contrast to spontaneous emission, which occurs at a characteristic rate for each of the atoms/oscillators in the upper energy state regardless of the external electromagnetic field.