Understanding and controlling charge energy flow in state-of-the-art semiconductor quantum wells has enabled high-efficiency optoelectronic devices. Two-dimensional (2D) Ruddlesden-Popper perovskites are solution-processed wherein the band gap can be tuned by varying perovskite-layer thickness, which modulates effective electron-hole confinement. We report that, counterintuitive to classical quantum-confined systems where photogenerated electrons holes strongly bound Coulomb interactions or...

Abstract Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack stability over prolonged irradiation. Few studies investigated effect light soaking on hybrid perovskites and attributed degradation in optoelectronic properties to photochemical or field-assisted ion migration. Here we show that slow photocurrent devices due formation light-activated meta-stable deep-level trap...

Structural ordering is widely present in molecules and materials. However, the organization of on curved surface nanoparticles still least understood owing to major limitations current characterization tools. By merits x-ray crystallography, we reveal structural at all scales a super robust 133-gold atom nanoparticle protected by 52 thiolate ligands, which manifested self-assembled hierarchical patterns starting from metal core interfacial -S-Au-S- ladder-like helical "stripes" further...

Solution-processed organometallic perovskites have rapidly developed into a top candidate for the active layer of photovoltaic devices. Despite remarkable progress associated with perovskite materials, many questions about fundamental photophysical processes taking place in these devices, remain open. High on list unexplained phenomena are very modest mobilities despite low charge carrier effective masses. Moreover, experiments elucidate unique degradation photocurrent affecting stable...

Defects are known to affect nanoscale phase transitions, but their specific role in the metal-to-insulator transition VO2 has remained elusive. By combining plasmon resonance nanospectroscopy with density functional calculations, we correlate decreased phase-transition energy oxygen vacancies created by strain at grain boundaries. measuring degree of metallization lithographically defined nanoparticles, find that hysteresis width narrows increasing size, thus illustrating potential for...

Polarization-controlled excitation of plasmonic modes in nanometric Au particle-on-film gaps is investigated experimentally using single-particle dark-field spectroscopy. Two distinct geometries are explored: nanospheres on top and inserted a thin gold film. Numerical simulations reveal that the three resonances arising scattering spectra measured for particles film originate from highly confined gap at interface. These feature different azimuthal characteristics, which consistent with...

Ultrafast photoinduced phase transitions could revolutionize data-storage and telecommunications technologies by modulating signals in integrated nanocircuits at terahertz speeds. In quantum phase-changing materials (PCMs), microscopic charge, lattice, orbital degrees of freedom interact cooperatively to modify macroscopic electrical optical properties. Although these interactions are well documented for bulk single crystals thin films, little is known about the ultrafast dynamics...

We have synthesized a series of asymmetric pentacene-tetracene heterodimers with variable-length conjugated bridge that undergo fast and efficient intramolecular singlet fission (iSF). These compounds distinct triplet energies, which allow us to study the spatial dynamics excitons during iSF process, including significant role exciton correlations in promoting pair generation recombination. demonstrate primary photoexcitations dimers are delocalized singlets enable iSF. However, these...

Nanoscale devices, such as all-optical modulators and electro-optical transducers, can be implemented in heterostructures that integrate plasmonic nanostructures with functional active materials. Here we demonstrate control of a nanoscale memory effect heterostructure by coupling the localized surface plasmon resonance (LSPR) gold nanodisk arrays to phase-changing material (PCM), vanadium dioxide (VO2). By latching VO2 distinct correlated metallic state during insulator-to-metal transition...

We have measured the size dependence of a solid-solid phase transformation in discrete nanoscale volumes vanadium dioxide (VO(2)) defined by split-ring resonators. By monitoring in-coupling plasmonic mode while thermally cycling through insulator-metal transition, we show that hysteresis width broadens with reduced interrogation volume (i.e., number intrinsic nucleation sites). The results further imply range over which both electronic and structural components switching exhibit similar dependence.

We present a detailed study of the photoinduced insulator-metal transition in VO${}_{2}$ with broadband time-resolved reflection spectroscopy. This allows us to separate response lattice vibrations from electronic dynamics and observe their individual evolution. When we excite above phase threshold, find that restoring forces describe ground-state monoclinic structure are lost during excitation process, suggesting an ultrafast change potential drives structural transition. However, by...

We present a computational design for an integrated electro-optic modulator based on near-field plasmonic coupling between gold nanodisks and thin film of vanadium dioxide silicon substrate. Active modulation is achieved by applying time-varying electric field to initiate large changes in the refractive index dioxide. Significant decrease device footprint (200 nm x 560 nm) increase extinction ratio per unit length (9 dB/µm) compared state-of-the-art photonic modulators are predicted.

We demonstrate thermally controlled plasmon resonance modulation of single gold nanoparticles on vanadium dioxide thin films by performing dark-field spectroscopy measurements at different temperatures. The the exhibits a significant blueshift in visible range when film undergoes its insulator-to-metal phase transition around 67 °C. More importantly, shift shows clear hysteresis, mirroring behavior film. At fixed wavelength, scattering intensity Au particles also hysteretic decorated with an...

A quantitative description of recombination processes in nanostructured semiconductor photocatalysts-one that distinguishes between bulk (charge transport) and surface (chemical reaction) losses-is critical for advancing solar-to-fuel technologies. Here we present an situ experimental framework determines the bias-dependent quantum yield ultrafast carrier transport to reactive interface. This is achieved by simultaneously measuring electrical characteristics subpicosecond charge dynamics a...

Manipulating optical signals below the diffraction limit is crucial for next-generation data-storage and telecommunication technologies. Although controlling flow of light around nanoscale waveguides was achieved over a decade ago, modulating at terahertz frequencies within volumes remains challenge. Since physics underlying any modulator relies on changes in dielectric properties, incorporation strongly electron-correlated materials (SECMs) has been proposed because they can exhibit orders...

Metasurfaces offer unparalleled functionalities for controlling the propagation and properties of electromagnetic waves. But to transfer these functions technological applications, it is critical render them tunable enable fast control by external stimuli. In most cases, this has been realized utilizing materials combined with a top-down nanostructuring process, which often complicated time intensive. Here we present novel strategy fabricating metasurface comprising epitaxially grown...

Efficient photovoltaic cells based on thin films of solution-processed 2D Ruddlesden–Popper hybrid perovskites (RPPs) represent an exciting breakthrough due to their enhanced tunability and chemical stability relative those fabricated from 3D phases. However, reports efficient charge separation current collection are in apparent contradiction with the well-known enhancement exciton binding energy multilayered halide perovskites, which should lower device's internal quantum efficiency...

With solar cells reaching 26.1% certified efficiency, hybrid perovskites are now the most efficient thin film photovoltaic material. Though substantial effort has focussed on synthesis approaches and device architectures to further improve perovskite-based cells, more work is needed correlate physical properties of underlying structure with performance. Here, using cathodoluminescence microscopy coupled unsupervised machine learning, we quantify how nanoscale heterogeneity globally builds up...

Semiconductor photoelectrodes for photoelectrochemical (PEC) water splitting require efficient carrier generation, separation, and transport at beyond the space charge region (SCR) formed aqueous interface. The trade-off between photon collection minority delivery governs photoelectrode design implies maximum efficiency an electrode thickness equivalent to light absorption depth. Here, using planar ZnO thin films as a model system, we identify photocarriers SCR another significant source...

A rapid increase in the atmospheric temperature has been reported recent years worldwide. The lack of proper aid to protect from exposure sun during working hours raised number sunburn cases among workers. It is important promote productive workplaces without compromising safety and health concerns. In present work, we report low-temperature plasma (LTP)-assisted tailoring surface properties fabrics reflect IR radiation sun. LTP technique can be adapted for thermally sensitive materials such...

As wide bandgap materials are nanostructured for optoelectronics and energy technologies, understanding how size defects modify the carrier dynamics becomes critical. Here, we examine broadband ultraviolet-visible subpicosecond emission of prototypical ZnO in bulk, nanowire nanosphere geometries. Using a high-sensitivity transient Kerr-based spectrometer, probe exciton low fluence regime to determine states impact thermalization recombination rates. In contrast steady-state measurements,...

We report on ultrafast optical investigations of the light-induced insulator-to-metal phase transition in vanadium dioxide with controlled disorder generated by substrate mismatch. These results reveal common dynamics this optically-induced that are independent disorder. Above fluence threshold for completing to rutile crystalline phase, we find a time scale, sample morphology, ps is consistent nucleation and growth R from parent M1 ground state.

Polymers are desirable optoelectronic materials, stemming from their solution processability, tunable electronic properties, and large absorption coefficients. An exciting development is the recent discovery that singlet fission (SF), conversion of a exciton to pair triplet states, can occur along backbone an individual conjugated polymer chain. Compared other intramolecular SF compounds, nature state in polymers remains poorly understood, hampering new materials with optimized excited...