Tertiary Amine Oxides as Perovskite Nanocrystal Ligands and Components of Polymeric Nanocomposites

As a class of semiconductor nanocrystals that exhibits high photoluminescence quantum yield (PLQY) at tunable wavelengths, perovskite nanocrystals (PNCs) are attractive candidates for optoelectronic and light emitting devices. However, attempts to optimize PNC integration into optoelectronic and light emitting devices suffer from PNC instability and loss of PL over time. Here, we describe the impact of organic and polymeric N-oxides when used in post-synthetic processing of PNCs, whereby a significant increase in quantum yield is observed in solution, and stable PL emission is obtained in polymeric nanocomposites. Specifically, when using aliphatic N-oxides in post-synthetic ligand exchange with CsPbBr₃ PNCs in solution, a substantial boost in PNC brightness was observed (~40% or more PLQY increase), followed by an alteration of the perovskite chemistry. However, when N-oxide substituents were positioned pendent to a poly(n-butyl methacrylate) backbone, the optically clear flexible nanocomposite films obtained had bright PL emission and maintained optical clarity, PL emission, and nanocrystal structure for months. Tertiary amine oxides are currently being investigated as small molecule aliphatic and polymeric ligands for lead-free perovskite nanocrystals, particularly Cs₃Cu₂I₅. In preliminary experiments, amine oxides have demonstrated an ability to bind to Cu-based NCs and improve dispersion. X-ray diffraction proved useful for characterizing the PNC crystal structure before and after ligand exchange, while electron microscopy (EM) and small-angle x-ray scattering (SAXS) measurements of the PNC-polymer nanocomposites are used to evaluate the ability of the polymeric N-oxide platform to cleanly disperse PNCs in flexible polymer films.