Colloidal synthesis and optical properties of heterostructured quantum wells

Abstract

Colloidal quantum wells (CQWs) have emerged as auspicious gain materials for next-generation colloidal nanolasers owing to their exceptional optoelectronic properties including intrinsically suppressed Auger recombination, large absorption cross-section, low cost of production, and the ability to precisely tailor their attributes. However, the realization of their photonic devices faces fundamental challenges inherent to semiconductor nanocrystals in general, which can be tackled via the design and engineering of their advanced heterostructures. In this thesis, we proposed multiple design strategies to address scientific obstacles associated with using such CQWs as gain materials and developed a variety of their rational heterostructure designs by implementing advanced synthesis techniques, allowing us to systematically study the structure-property relationship. We investigated the optical gain performance of these CQW heterostructures through spectral and temporal spectroscopy techniques to elucidate the underlying mechanisms, which guided us to improve the associated structural aspects of CQWs. This approach culminated in the development of superior CQW heterostructures possessing low optical gain thresholds, giant material gain coefficients, and long gain lifetimes, addressing all main specifications quantifying the quality of a gain material. We also presented proof-of-concept device demonstrations showcasing the advancement in the gain aspect of these CQW heterostructures, such as high-performance amplified spontaneous emission in solution and whispering gallery mode lasing with ultra-low thresholds. The findings of this thesis indicate highly engineered CQW heterostructures offer excellent gain media.