Fano resonances giving rise to a rich variety of asymmetric spectral shapes have been investigated in optical nanostructures with multidimensional configurations. However, 1D nanostructure realizing ...Fano resonances with well‐controlled spectral shapes are yet to be demonstrated. Here, the authors present both numerically and experimentally a 1D nanostructure exhibiting rich Fano resonances induced by interference between a lossy background (continuum) provided by a metal thin film and a discrete optical Tamm state (OTS). A drastic change in the Fano line shape occurs from a narrowband perfect absorber into a narrowband perfect reflector by controlling the metal thin film. Independent from the metal‐related Fano profile, the OTS component determines the resonance frequency and guarantees a sharp resonance (with quality factors over 1000) on the flat mirror background. Taking advantage of its high‐Q property, the structure can be developed into a dispersion device with subnanometer spectral resolution, which even enables a direct imaging of spectral information of molecular fingerprint. The authors believe that this work not only demonstrates a planar nanostructure with versatile Fano resonances for various applications but also provides physical insights into how a metal thin film can induce and significantly affect the Fano resonances in 1D optical resonators.
The investigated 1D structure consists of a thin metal film on top of an OTS resonator (DBR1 + DBR2). A wide range of Fano line shapes (in absorptance spectra) with a narrow bandwidth (Q above 1000) can be obtained (from narrowband perfect absorber to narrowband perfect reflector) by utilizing different metals as the top layer.
Silicon solar cells among different types of solar energy harvesters have entered the commercial market owing to their high power conversion efficiency and stability. By replacing the electrode and ...the p‐type layer by a single layer of carbon nanotubes, the device can be further simplified. This greatly augments the attractiveness of silicon solar cells in the light of raw material shortages and the solar payback period, as well as lowering the fabrication costs. However, carbon nanotube‐based silicon solar cells still lack device efficiency and stability. These can be improved by chemical doping, antireflection coating, and encapsulation. In this work, the multifunctional effects of p‐doping, antireflection, and encapsulation are observed simultaneously, by applying a polymeric acid. This method increases the power conversion efficiency of single‐walled carbon nanotube‐based silicon solar cells from 9.5% to 14.4% and leads to unprecedented device stability of more than 120 d under severe conditions. In addition, the polymeric acid‐applied carbon nanotube‐based silicon solar cells show excellent chemical and mechanical robustness. The obtained stable efficiency stands the highest among the reported carbon nanotube‐based silicon solar cells.
Polymeric acid dopants in single‐walled carbon nanotube‐laminated silicon solar cells show multifunctional effects; strong and permanent p‐doping, antireflection, and encapsulation. A record‐high power conversion efficiency of 14.4% with a device stability of more than 120 d is obtained herein owing to the multifunctional effects that improve all three photovoltaic parameters upon application of the dopant.
An increasing number of applications using ultraviolet radiation have renewed interest in ultraviolet photodetector research. Particularly, solar‐blind photodetectors sensitive to only deep UV (<280 ...nm), have attracted growing attention because of their wide applicability. Among recent advances in UV detection, nanowire (NW)‐based photodetectors seem promising, however, none of the reported devices possesses the required attributes for practical solar‐blind photodetection, namely, an efficient fabrication process, a high solar light rejection ratio, a low photocurrent noise, and a fast response. Herein, the assembly of β‐Ga2O3 NWs into high‐performance solar‐blind photodetectors by use of an efficient bridging method is reported. The device is made in a single‐step chemical vapor deposition process and has a high 250‐to‐280‐nm rejection ratio (∼2 × 103), low photocurrent fluctuation (<3%), and a fast decay time (<<20 ms). Further, variations in the synthesis parameters of the NWs induce drastic changes in the photoresponse properties, which suggest a possibility for tuning the performance of the photodetectors. The efficient fabrication method and high performance of the bridged β‐Ga2O3 NW photodetectors make them highly suitable for solar‐blind photodetection.
β‐Ga2O3 nanowires are assembled into a bridged structure in a single‐step chemical vapor deposition process. High responsivity, fast photocurrent decay, and excellent spectral selectivity for solar‐blind photodetection are demonstrated with the bridged β‐Ga2O3 nanowires. Investigations into the effects of defect densities in β‐Ga2O3 nanowires show that their photoresponse properties could be tailored for different applications.
Lead halide perovskites exhibit extraordinary optoelectronic performances and are being considered as a promising medium for high‐quality photonic devices such as single‐mode lasers. However, for ...perovskite‐based single‐mode lasers to become practical, fabrication and integration on a chip via the standard top‐down lithography process are strongly desired. The chief bottleneck to achieving lithography of perovskites lies in their reactivity to chemicals used for lithography as illustrated by issues of instability, surface roughness, and internal defects with the fabricated structures. The realization of lithographic perovskite single‐mode lasers in large areas remains a challenge. In this work, a self‐healing lithographic patterning technique using perovskite CsPbBr3 nanocrystals is demonstrated to realize high‐quality and high‐crystallinity single‐mode laser arrays. The self‐healing process is compatible with the standard lithography process and greatly improves the quality of lithographic laser cavities. A single‐mode microdisk laser array is demonstrated with a low threshold of 3.8 µJ cm−2. Moreover, the control of the lasing wavelength is made possible over a range of up to 6.4 nm by precise fabrication of the laser cavities. This work presents a general and promising strategy for standard top‐down lithography fabrication of high‐quality perovskite devices and enables research on large‐area perovskite‐based integrated optoelectronic circuits.
Large‐area single‐mode laser arrays are achieved through a self‐healing lithographic patterning technique by using CsPbBr3 nanocrystals. The self‐healing process is compatible with the standard lithography and enables the fabrication of high‐quality perovskite cavities with a significantly improved lasing performance. The fabricated single‐mode laser is realized with a low threshold of 3.8 µJ cm−2 and wavelength controllability up to 6.4 nm.
Plasmonic nanolasers provide a valuable opportunity for expanding sub‐wavelength applications. Due to the potential of on‐chip integration, semiconductor nanowire (NW)‐based plasmonic nanolasers that ...support the waveguide mode attract a high level of interest. To date, perovskite quantum dots (QDs) based plasmonic lasers, especially nanolasers that support plasmonic‐waveguide mode, are still a challenge and remain unexplored. Here, metallic NW coupled CsPbBr3 QDs plasmonic‐waveguide lasers are reported. By embedding Ag NWs in QDs film, an evolution from amplified spontaneous emission with a full width at half maximum (FWHM) of 6.6 nm to localized surface plasmon resonance (LSPR) supported random lasing is observed. When the pump light is focused on a single Ag NW, a QD‐NW coupled plasmonic‐waveguide laser with a much narrower emission peak (FWHM = 0.4 nm) is realized on a single Ag NW with the uniform polyvinylpyrrolidone layer. The QDs serve as the gain medium while the Ag NW serves as a resonant cavity and propagating plasmonic lasing modes. Furthermore, by pumping two Ag NWs with different directions, a dual‐wavelength lasing switch is realized. The demonstration of metallic NW coupled QDs plasmonic nanolaser would provide an alternative approach for ultrasmall light sources as well as fundamental studies of light matter interactions.
Quantum dot (QD)‐nanowire (NW) based plasmonic lasers are demonstrated by embedding Ag NWs in a CsPbBr3 QDs film. The evolution from amplified spontaneous emission to a localized surface plasmon resonance‐supported random lasing is observed. Further, a plasmonic‐waveguide laser is also achieved with a narrow bandwidth of 0.4 nm. By using the QD‐NW plasmonic‐waveguide lasers, a dual‐wavelength nanolaser switch is realized.
Laser devices produced via solution‐processed perovskite quantum dots (QDs) offer broad spectral tunability as well as ease of fabrication. Utilizing quasi‐bound states in the continuum (quasi‐BIC) ...modes, solution‐processed QD laser devices have been demonstrated with a nanostructure coated in a thin‐film gain media configuration. However, light leakage through thin‐film guiding from the cavity side edges becomes more pronounced when shrinking the cavity size, posing challenges for the miniaturization of quasi‐BIC‐based lasers. Here, the fabrication of well‐defined patterns of QDs via a solution process allows them to take advantage of the pattern edges to reduce losses through the cavity edges. A single‐mode BIC laser is reported by using CsPbBr3 QDs with a narrow linewidth of ≈0.1 nm. Importantly, a miniaturized quasi‐BIC laser is realized with a device size as small as 10 × 10 µm2, making it the smallest among existing solution‐processed BIC lasers. This work provides a strategy for developing ultra‐compact BIC lasers via solution‐processed gain media.
CsPbBr3 Quantum dot (QD) cavity‐supported BIC lasers are demonstrated by integrating an isolated CsPbBr3 QD cavity on a TiO2 nanocylinder array. The fabrication of well‐defined patterns of QDs via a solution process allows us to take advantage of the pattern edges to reduce losses. Finally, lasing with a miniaturized BIC laser having a cavity size down to 10 × 10 µm2 is achieved making it the smallest among existing solution‐processed BIC lasers.
Although chiral semiconductors have shown promising progress in direct circularly polarized light (CPL) detection and emission, they still face potential challenges. A chirality‐switching mechanism ...or approach integrating two enantiomers is needed to discriminate the handedness of a given CPL; additionally, a large material volume is required for sufficient chiroptical interaction. These two requirements pose significant obstacles to the simplification and miniaturization of the devices. Here, room‐temperature chiral polaritons fulfilling dual‐handedness functions and exhibiting a more‐than‐two‐order enhancement of the chiroptical signal are demonstrated, by embedding a 40 nm‐thick perovskite film with a 2D chiroptical effect into a Fabry–Pérot cavity. By mixing chiral perovskites with different crystal structures, a pronounced 2D chiroptical effect is accomplished in the perovskite film, featured by an inverted chiroptical response for counter‐propagating CPL. This inversion behavior matches the photonic handedness switch during CPL circulation in the Fabry–Pérot cavity, thus harvesting giant enhancement of the chiroptical response. Furthermore, affected by the unique quarter‐wave‐plate effects, the polariton emission achieves a chiral dissymmetry of ±4% (for the emission from the front and the back sides). The room‐temperature polaritons with the strong dissymmetric chiroptical interaction shall have implications on a fundamental level and future on‐chip applications for biomolecule analysis and quantum computing.
The light–matter interaction between a 2D chiroptical film and a Fabry–Pérot cavity is investigated. The chiroptical response inversion of the 2D chiroptical film shall be ideally suited to the circularly polarized light switching feature in the Fabry–Pérot cavity, resulting in the enhancement effect in the chiroptical signal.
Electrophoretic deposition (EPD) is a versatile technique that has drawn attention due to its ease of use and performance in depositing high-quality layers at room temperature. This technique ...principle is based on the deposition of charged particles from a stable colloidal suspension on a conductive substrate using either a direct or alternating current. Using relatively simple and low-cost equipment, the EPD technique enables the deposition of layers with controlled microstructures at nanoscale. The EPD technique has been particularly successful in the fabrication of the electrocatalyst layers for low-temperature fuel cells, which are anchored on the top of the fuel cell electrodes. In comparison with other electrocatalyst layer deposition techniques such as drop-casting, the EPD technique offers clear advantages for the control of the thickness and packing density of the electrocatalyst layers. Owing to the dense packing density, electrocatalyst layers deposited by EPD could achieve enhanced conductivity and efficiency. The present review aims at comprehensively evaluating the recently published results on the electrocatalyst layers fabricated by EPD and applied in oxygen reduction reactions, alcohol electro-oxidation reactions, hydrogen evolution reactions, and oxygen evolution reactions.
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•The preparation of electrocatalysts is an important issueto commercialize electrochemical energy conversion systems.•The standard drop-casting method mainly suffers from its lack of control.•EPD technique is a means to fabricate highly efficient and low-cost electrocatalyst.•This review discusses deeply electrocatalyst fabrication by EPD process.
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