Thesis Defense: Optical and Structural Studies of Nanocrystal Assemblies

Quantum photonic devices require robust sources of single photons to perform basic computational and communication protocols. Thus, developing scalable, integrable, and efficient quantum light sources has become crucial for the realization of quantum photonic devices. Single quantum dots are promising candidates as quantum light sources due to their ability to show size-tunable emission. However, isolating a single quantum dot and integrating it with other components to create a device with high reliability is a challenging endeavor. Here I develop a possible method to address this challenge by attaining single photon emission from a cluster of quantum dots. I achieved this by coupling quantum dots using a plasmonic nanoparticle. I found that the photoluminescence intensity of the plasmon-coupled quantum dots fits well with a single sublinear power law exponent, which is distinct from the behavior of bare quantum dot aggregates. To evaluate the robustness of this phenomenon, I have considered both monometallic (Au) and bimetallic (Au-Ag) particles with different plasmon damping characteristics. Further, I discuss the possible role of emerging excitonic interactions in the plasmon-coupled system. Quite noticeably, it was observed that plasmon coupling results in reduced flickering, thus enabling the realization of a more stable and reliable single photon source. In my presentation I will also discuss certain optical and structural aspects of these bimetallic nanoparticles. I will especially focus upon how an inhomogeneous incorporation of one metal into another modifies the dielectric function of the bimetallic nanoparticle. Also, I will show how the tendency of these nanoparticles to oxidize may be employed in batteries. In particular, I describe my work towards using these nanoparticles as cathode material for Zn-Ag battery. Our obtained results are broadly useful in the development of silver-based Zn-Ag batteries where material losses and electrode deformation are known to limit rechargeability.