Prospects and challenges of colloidal quantum dot laser diodes

Colloidal quantum dots (QDs) combine the superior light-emission characteristics of quantum-confined semiconductors with the chemical flexibility of molecular systems. These properties could, in principle, enable solution-processable laser diodes with an ultrawide range of accessible colours. However, the realization of such devices has been hampered by fast optical gain decay due to non-radiative Auger recombination and poor stability of QD solids at the high current densities required for the lasing regime. Recently, these problems have been resolved, which resulted in the development of electrically pumped optical gain devices operating at ultrahigh current densities of around 1,000 A cm−2. The next step is the realization of a QD laser diode (QLD). Here we assess the status of the QD lasing field, examine the remaining challenges on the path to a QLD and discuss practical strategies for attaining electrically pumped QD lasing. Colloidal quantum dots may offer solution-processable lasers, with a wide range of colours available. Technical hurdles and progress towards realization of useful quantum dot laser diodes is reviewed.