Browsing by Author "Schwartzberg, Adam M."

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Anisotropic 2D excitons unveiled in organic–inorganic quantum wells
(Royal Society of Chemistry, 2020-11) Maserati, Lorenzo; Refaely-Abramson, Sivan; Kastl, Christoph; Chen, Christopher T.; Borys, Nicholas J.; Eisler, Carissa N.; Collins, Mary S.; Smidt, Tess E.; Barnard, Edward S.; Strasbourg, Matthew; Schriber, Elyse A.; Shevitski, Brian; Yao, Kaiyuan; Hohman, J. Nathan; Schuck, P. James; Aloni, Shaul; Neaton, Jeffrey B.; Schwartzberg, Adam M.
Hybrid layered metal chalcogenide crystalline polymer hosts strongly anisotropic two-dimensional excitons with large binding energies.
Electrically driven photon emission from individual atomic defects in monolayer WS2
(2020-09) Schuler, Bruno; Cochrane, Katherine A.; Kastl, Christoph; Barnard, Edward S.; Wong, Edward; Borys, Nicholas J.; Schwartzberg, Adam M.; Ogletree, D. Frank; Garcia de Abajo, F. Javier; Weber-Bargioni, Alexander
Quantum dot–like single-photon sources in transition metal dichalcogenides (TMDs) exhibit appealing quantum optical properties but lack a well-defined atomic structure and are subject to large spectral variability. Here, we demonstrate electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlate the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Atomically resolved emission maps of individual point defects closely resemble electronic defect orbitals, the final states of the optical transitions. Inelastic charge carrier injection into localized defect states of two-dimensional materials provides a powerful platform for electrically driven, broadly tunable, atomic-scale single-photon sources.
Long-Range Exciton Diffusion in Two-Dimensional Assemblies of Cesium Lead Bromide Perovskite Nanocrystals
(2020-05) Penzo, Erika; Loiudice, Anna; Barnard, Edward S.; Borys, Nicholas J.; Jurow, Matthew J.; Lorenzon, Monica; Rajzbaum, Igor; Wong, Edward K.; Liu, Yi; Schwartzberg, Adam M.; Cabrini, Stefano; Whitelam, Stephen; Buonsanti, Raffaella; Weber-Bargioni, Alexander
Förster resonant energy transfer (FRET)-mediated exciton diffusion through artificial nanoscale building block assemblies could be used as an optoelectronic design element to transport energy. However, so far, nanocrystal (NC) systems supported only diffusion lengths of 30 nm, which are too small to be useful in devices. Here, we demonstrate a FRET-mediated exciton diffusion length of 200 nm with 0.5 cm2/s diffusivity through an ordered, two-dimensional assembly of cesium lead bromide perovskite nanocrystals (CsPbBr3 PNCs). Exciton diffusion was directly measured via steady-state and time-resolved photoluminescence (PL) microscopy, with physical modeling providing deeper insight into the transport process. This exceptionally efficient exciton transport is facilitated by PNCs’ high PL quantum yield, large absorption cross section, and high polarizability, together with minimal energetic and geometric disorder of the assembly. This FRET-mediated exciton diffusion length matches perovskites’ optical absorption depth, thus enabling the design of device architectures with improved performances and providing insight into the high conversion efficiencies of PNC-based optoelectronic devices.