The development of optical gain in chemically synthesized semiconductor nanoparticles (nanocrystal quantum dots) has been intensely studied as the first step toward nanocrystal dot lasers. We examined competing dynamical processes involved amplification and lasing dots found that, despite a highly efficient intrinsic nonradiative Auger recombination, large can be developed at wavelength emitting transition for close-packed solids these dots. Narrowband stimulated emission with pronounced...

Scintillators, which are capable of converting ionizing radiation into visible photons, an integral part medical, security, and commercial diagnostic technologies such as X-ray imaging, nuclear cameras, computed tomography. Conventional scintillator fabrication typically involves high-temperature sintering, generating agglomerated powders or large bulk crystals, pose major challenges for device integration processability. On the other hand, colloidal quantum dot scintillators cannot be cast...

We study different emission regimes in close-packed films of chemically synthesized CdSe nanoparticles [nanocrystal quantum dots (NQDs)]. observe that the NQD photoluminescence is dominated by excitons and biexcitons, respectively, before after threshold for stimulated emission. Furthermore, we demonstrate regime microring lasing into sharp, whispering-gallery modes using solids incorporated microcapillary tubes. This result indicates a feasibility miniature, solid-state laser devices based on NQDs.

Biexciton photoluminescence (PL) quantum yields (Q(2X)) of individual CdSe/CdS core-shell nanocrystal dots with various shell thicknesses are derived from independent PL saturation and two-photon correlation measurements. We observe a near-unity Q(2X) for some nanocrystals an ultrathick 19-monolayer shell. High Q(2X)'s are, however, not universal vary widely among nominally identical indicating significant dependence upon subtle structural differences. Interestingly, our measurements...

The development of nanocrystal quantum dots (NQDs) with suppressed nonradiative Auger recombination has been an important goal in colloidal nanostructure research motivated by the needs prospective applications lasing devices, light-emitting diodes, and photovoltaic cells. Here, we conduct single-nanocrystal spectroscopic studies recently developed core−shell NQDs (so-called "giant" NQDs) that comprise a small CdSe core surrounded 16-monolayer-thick CdS shell. Using both continuous-wave...

Organic–inorganic hybrid perovskite materials have recently evolved into the leading candidate solution-processed semiconductor for solar cells due to their combination of desirable optical and charge transport properties. Chief among these properties is long carrier diffusion length, which essential optimizing device architecture performance. Herein, we used time-resolved photoluminescence (at low excitation fluence, 10.59 μJ·cm–2 upon two-photon excitation), most accurate direct approach...

We perform side-by-side comparison of optical gain properties spherical and elongated nanocrystals (quantum dots quantum rods, respectively). This indicates that nanoparticles provide several features beneficial for lasing applications, such as enhanced absorption cross sections (and hence reduced threshold improved photostability), increased lifetime, extended spectral range through the use transitions involve both ground excited electronic states.

We report a systematic study of photoluminescence (PL) intensity and lifetime fluctuations in individual CdSe/CdS core/shell nanocrystal quantum dots (NQDs) as function shell thickness. show that while at low pump intensities PL blinking thin-shell (4-7 monolayers, MLs) NQDs can be described by random switching between two states high (ON) (OFF) emissivities, it changes to the regime with continuous distribution ON levels powers. A similar behavior is observed samples medium thickness (10-12...

The rapid development of perovskite solar cells has focused its attention on defects in perovskites, which are gradually realized to strongly control the device performance. A fundamental understanding is therefore needed for further improvement this field. Recent efforts have mainly minimizing surface and grain boundaries thin films. Using time-resolved photoluminescence spectroscopy, we show that bulk samples prepared using vapor assisted solution process (VASP) play a key role addition...

Cesium lead halide perovskite materials have attracted considerable attention for potential applications in lasers, light-emitting diodes, and photodetectors. Here, we provide the experimental theoretical evidence photon recycling CsPbBr3 microwires. Using two-photon excitation, recorded photoluminescence (PL) lifetimes emission spectra as a function of lateral distance between PL excitation collection positions along microwire, with separations exceeding 100 μm. At longer separations,...

Polycyclic aromatic hydrocarbons such as perylene and pyrene their derivatives are highly emissive fluorophores in solution. However, the practical applications of these materials field molecular electronic light-emitting devices often hindered by self-quenching effects because formation nonfluorescent aggregates concentrated solutions or solid state. Herein, we demonstrate that aggregation-caused quenching perylenes can be minimalized incorporation into metal-organic frameworks (MOFs). This...

Strain-engineering in 2D transition metal dichalcogenide (TMD) semiconductors has garnered intense research interest tailoring the optical properties via strain-induced modifications of electronic bands TMDs, while its impact on exciton dynamics remains less understood. To address this, an extensive study transient absorption (TA) both W- and Mo-based single-crystalline monolayer TMDs grown by a recently developed laser-assisted evaporation method is performed. All spectral features...

Auger decay of multiple excitons represents a significant obstacle to photonic applications semiconductor quantum dots (QDs). This nonradiative process is particularly detrimental the performance QD-based electroluminescent and lasing devices. Here, we demonstrate that shells with an "inverted" QD geometry inhibit recombination, allowing substantial improvements their multiexciton characteristics. By promoting spatial separation between excitons, shell leads ultralong biexciton lifetimes...

Many optoelectronic processes in colloidal semiconductor nanocrystals (NCs) suffer an efficiency decline under high-intensity excitation. This issue is caused by Auger recombination of multiple excitons, which converts the NC energy into excess heat, reducing and life span NC-based devices, including photodetectors, X-ray scintillators, lasers, high-brightness light-emitting diodes (LEDs). Recently, quantum shells (QSs) have emerged as a promising geometry for suppression decay; however,...

The preparation of CdSe nanocrystal quantum dot (NQD)–titania nanocomposites (see Figure) exhibiting large NQD packing densities and high photoluminescence efficiencies is described. These new materials show both third‐order nonlinear susceptibilities optical gain. Furthermore, micro‐ring lasing efficient dynamic holographic gratings using these are demonstrated.

A potential complication associated with the realization of optical-gain regime in semiconductor nanocrystals (NCs) arises from competing phenomenon excited-state absorption. Here, we apply an ultrafast transient absorption technique to study competition between optical gain and (photoinduced) CdSe NCs as a function NC size, surface passivation, solvent/matrix identity. We observe that for prepared such commonly used solvent hexane, contribution photoinduced rapidly increases decreasing...

We study the effect of multiparticle interactions on optical gain and stimulated emission in close-packed solids chemically synthesized CdSe nanocrystals (nanocrystal quantum dots). An analysis pump-dependent nonlinear absorption signals indicates that band-edge is due to states with a dominant contribution from doubly excited (quantum-confined biexcitons). observe dynamics are competition between ultrafast hole surface trapping Auger decay. analyze intrinsic recombination lifetimes pump...

We demonstrate efficient excitonic sensitization of crystalline Si nanomembranes via combined effects radiative (RET) and nonradiative (NRET) energy transfer from a proximal monolayer colloidal semiconductor nanocrystals. Ultrathin, 25-300 nm films are prepared on top insulating SiO(2) substrates grafted with CdSe/ZnS nanocrystals carboxy-alkyl chain linkers. The wet chemical preparation ensures that surfaces fully passivated negligible number surface state defects the separation between is...

We studied the competition between energy loss due to quenching and enhanced absorption arising from near-field plasmonic effect of Au nanoparticles (NPs) on performance organic solar cells (OSCs), by fabricating inverted architecture OSCs with electron transport layers consisting an NPs monolayer covered a ZnO overlayer. The distance poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) active layer was controlled systematically varying overlayer thickness, its...

Toward a truly photostable PbSe quantum dot (QD), we apply the thick-shell or "giant" QD structural motif to this notoriously environmentally sensitive nanocrystal system. Namely, using sequential application of two shell-growth techniques-partial-cation exchange and successive ionic layer adsorption reaction (SILAR)-we are able overcoat QDs with sufficiently thick CdSe shells impart new single-QD-level photostability, as evidenced by suppression both photobleaching blinking behavior. We...

Ultrafast transient pump-probe measurements of thin ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{PbI}}_{3}$ perovskite films over a wide spectral range from 350 to 800 nm reveal family photoinduced bleach (PB) and absorption (PA) features unequivocally pointing the fundamentally multiband character underlying electronic structure. Excitation pump-energy dependent kinetics three long-lived PB peaks at 1.65, 2.55, 3.15 eV along with broad PA band shows involvement band-edge thermalized carriers...

Abstract Cesium-based perovskite nanocrystals (PNCs) possess alluring optical and electronic properties via compositional structural versatility, tunable bandgap, high photoluminescence quantum yield facile chemical synthesis. Despite the recent progress, origins of emission in various types PNCs remains unclear. Here, we study photon from individual three-dimensional zero-dimensional cesium lead bromide PNCs. Using antibunching lifetime measurements, demonstrate that statistics both type...

We synthesized PbS/CdS core/shell quantum dots (QDs) to have functional single-emitter properties for room-temperature, solid-state operation in the telecom O and S bands. Two shell-growth methods—cation exchange successive ionic layer adsorption reaction (SILAR)—were employed prepare QD heterostructures with shells of 2–16 monolayers. QDs were sufficiently bright stable resolve photoluminescence (PL) spectra representing both bands from single nanocrystals using standard detection methods,...