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Intrinsic defects such as vacancies, interstitials, and anti-sites often introduce rich luminescent properties in II-VI semiconductor nanomaterials. A clear understanding of the dynamics of the defect-related excitons is particularly important for the design and optimization of nanoscale optoelectronic devices. In this paper, low-temperature steady-state(More)
The ultrafast saturable absorption in graphene is experimentally and theoretically investigated in the femtosecond (fs) time regime. This phenomenon is well-modeled with valence band depletion, conduction band filling and ultrafast intraband carrier thermalization. The latter is dominated by intraband carrier-carrier scattering with a scattering time of 8 ((More)
Low-temperature solution-processed materials that show optical gain and can be embedded into a wide range of cavity resonators are attractive for the realization of on-chip coherent light sources. Organic semiconductors and colloidal quantum dots are considered the main candidates for this application. However, stumbling blocks in organic lasing include(More)
Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in(More)
Constrained by large ohmic and radiation losses, plasmonic nanolasers operated at visible regime are usually achieved either with a high threshold (10(2)-10(4) MW cm(-2)) or at cryogenic temperatures (4-120 K). Particularly, the bending-back effect of surface plasmon (SP) dispersion at high energy makes the SP lasing below 450 nm more challenging. Here we(More)
Organic-inorganic hybrid perovskites have cemented their position as an exceptional class of optoelectronic materials thanks to record photovoltaic efficiencies of 22.1%, as well as promising demonstrations of light-emitting diodes, lasers, and light-emitting transistors. Perovskite materials with photoluminescence quantum yields close to 100% and(More)
Ultralow-threshold two-photon pumped amplified spontaneous emission (2ASE) and lasing in seeded CdSe/CdS nanodot/nanorod heterostructures is demonstrated for the first time. Such heterostructures allow the independent tunability of the two-photon absorption (2PA) cross-section (σ(2)) through varying the CdS rod size, and that of the emission wavelength(More)
Understanding the optical gain and mode-selection mechanisms in semiconductor nanowire (NW) lasers is key to the development of high-performance nanoscale oscillators, amplified semiconductor/plasmon lasers and single photon emitters, and so forth. Modification of semiconductor band structure/bandgap through electric field modulation, elemental doping, or(More)
There has been much controversy over the incorporation of organic-ligand-encapsulated plasmonic nanoparticles in the active layer of bulk heterojunction organic solar cells, where both enhancement and detraction in performance have been reported. Here through comprehensive transient optical spectroscopy and electrical characterization, we demonstrate(More)
Near-infrared (NIR) solid-state micro/nanolasers are important building blocks for true integration of optoelectronic circuitry. Although significant progress has been made in III-V nanowire lasers with achieving NIR lasing at room temperature, challenges remain including low quantum efficiencies and high Auger losses. Importantly, the obstacles toward(More)