Colloidal Semiconductor Nanocrystal Lasers and Laser Diodes

Lasers and optical amplifiers based on solution-processablematerialshave been long-desired devices for their compatibility with virtuallyany substrate, scalability, and ease of integration with on-chip photonicsand electronics. These devices have been pursued across a wide rangeof materials including polymers, small molecules, perovskites, andchemically prepared colloidal semiconductor nanocrystals, also commonlyreferred to as colloidal quantum dots. The latter materials are especiallyattractive for implementing optical-gain media as in addition to beingcompatible with inexpensive and easily scalable chemical techniques,they offer multiple advantages derived from a zero-dimensional characterof their electronic states. These include a size-tunable emissionwavelength, low optical gain thresholds, and weak sensitivity of lasingcharacteristics to variations in temperature. Here we review the statusof colloidal nanocrystal lasing devices, most recent advances in thisfield, outstanding challenges, and the ongoing progress toward technologicalviable devices including colloidal quantum dot laser diodes.