Correlating Photoluminescence with Total Volume in Suspended Binary Superlattices of Infrared Colloidal Nanocrystals Using Transmission Electron Microscopy

By combining infrared semiconductor colloidal nanocrystals (NCs) into three-dimensional superlattices, new optoelectronic properties become available and are controllable through careful choice of the constituent nanocrystals and their chemical interactions. Here, we fabricate large (>1 μm) domains of binary nanocrystal superlattices made up of infrared plasmonic Cu_2-xS/PbS core/shell and excitonic PbS nanocrystals, which are suspended over holes for further transmission electron microscopy and optical characterization. We determine both thickness and spatial extent of the superlattice to define the local volume in individual superlattice domains, which directly correlates to photoluminescence. Combined with time-resolved photoluminescence spectroscopy, these results indicate that energy transfer occurs between the excitonic emitters and plasmonic nanocrystals, which we will discuss in context with computational investigations.