Synthetic Design of Optical Emitters

Abstract

Humanity’s ability to control and harness the power of light lies at the core of what defines much of our lives today, with a great wealth of future technologies on the horizon. Colloidal emitters, such as quantum dots (QDs) and small molecules, act as chemical platforms with extraordinary capabilities in shaping light-matter interactions. Yet, the stringent requirements placed on these species by increasingly sophisticated applications demand the continuous synthetical improvement, as well as the development of conceptually new, classes of emitters.

In the first part of this thesis, I detail a new approach to the precursor chemistry of indium arsenide (InAs) QDs based on the redox chemistry of In. The judicious combination of an As(III) and an In(I) precursor yields an atomeconomical redox couple employing safe and commercially available compounds. A pre-equilibrium based on the disproportionation of In(I) to In(III) and In(0) confers robustness and flexibility to the particle growth. The emission of these InAs-based QDs is shown to cover much of the near infrared (NIR) and shortwave infrared (SWIR), opening up new pathways to sensing and imaging technologies.

In the second part, I describe the development of a versatile class of surface ligands for lead halide perovskite (LHP) QDs of CsPbBr3. CsPbBr3 QDs have seen tremendous development in recent years, positing them as candidate emitters for quantum optical applications. Carefully constructing binding groups and backbones tailored to the LHP surface furnishes a class of dicationic quaternary ammonium (Diquat) ligands. The influence of these ligands leads to effective electronic passivation and modulation of phonon coupling, observed in the form of narrowed emission linewidths, bulk-like Stokes shifts, mitigated inhomogeneous lineshape broadening, and an increased fraction of photons emitted into the coherent channel.

In the final chapter, I translate emissive defects found in hexagonal boron nitride (hBN) matrices to small molecule emitters. By leveraging the covalent and two-dimensional nature of hBN, defect motives comprising as little as 3 atoms could potentially be embedded in a molecular framework while retaining their defining characteristics. A concise synthetic scheme covering multiple defect-derived structures is provided, opening the door to novel rationally designed emitters.