Dr. Maksym Kovalenko

Abstract:

LHP NCs are of broad interest as classical light sources (LED/LCD displays) and quantum light sources (quantum sensing and imaging, quantum communication, optical quantum computing). The surface-functionalization of such labile ionic materials poses a formidable challenge, which we address with the library of designer phospholipid capping ligands [1]. Lattice-matched primary-ammonium phospholipids enhance the structural and colloidal integrity of hybrid organic–inorganic NCs [FAPbBr₃ and MAPbBr₃ (FA, formamidinium; MA, methylammonium)] and lead-free metal halide NCs. The molecular structure of the organic ligand tail governs the long-term colloidal stability and compatibility with solvents of diverse polarity, from hydrocarbons to alcohols. These NCs exhibit photoluminescence (PL) quantum yield of more than 96% in solution and solids, as well as hours-long stability at a single-particle level, with minimal PL intermittency, as well as bright and high-purity (about 95%) single-photon emission.  The brightness of such a quantum emitter is ultimately described by Fermi’s golden rule, where a radiative rate proportional to its oscillator strength (intrinsic emitter property) and the local density of photonic states (photonic engineering, i.e. cavity). With perovskite NCs, we present a record-low sub-100 ps radiative decay time for CsPb(Br/Cl)₃ NCs by the NC size increase to 30 nm, owing to the giant oscillator strength [2]. Notably, the fast radiative rate is achieved along with the single-photon emission. When such bright and coherent QDs are assembled into superlattices, collective properties emerge, such as superradiant emission from the inter-NC coupling [3]. In the most recent work [4], we present the formation of multicomponent SLs made from the CsPbBr₃ NCs of two different sizes. The diversity of obtained SLs encompassed the binary ABO₆-, ABO₃-, and NaCl-type structures, all of which contained orientationally and positionally confined NCs. We observed efficient NC coupling and Förster-like energy transfer from strongly confined 5.3 nm CsPbBr₃ NCs to weakly confined 17.6 nm CsPbBr₃ NCs. Exciton spatiotemporal dynamics measurements reveal that binary SLs exhibit enhanced exciton diffusivity compared to one-component SLs.