Nanophoton (Brazil)

Phenylethylammonium (PEA) organic spacer-based quasi-two-dimensional (Q-2D) perovskites have garnered considerable attention due to their tunable optoelectronic properties and high environmental stability. However, the response speed and responsivity of PEA-based Q-2D perovskite photodiodes (Q-2D PPDs) remain limited by inadequate carrier transport and collection. Herein, we propose a simple yet effective crystal orientation control strategy to overcome these limitations. Compositional engineering of the photoactive layer is employed to suppress defect formation and promote out-of-plane crystal orientation, which facilitates carrier transport in vertical n–i–p photodiodes. Concurrently, the optimized surface morphology of the Q-2D perovskite film enables the implementation of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as a hole transport layer to enhance hole extraction, block interfacial electron injection, and reduce dark leakage current. Our self-powered Q-2D PPDs, featuring a device architecture of ITO/SnO2/(4F-PEA)2(MA)3Pb4I11Cl2/PTAA/Au, exhibit ultrafast response times of 2.5 μs/1.9 μs (rise/fall), a responsivity of 0.25 A/W, and a detectivity of 3.4 × 1012 Jones at 550 nm. Notably, the unencapsulated detectors show excellent operational stability for over 180 days under ambient conditions. The remarkable detection performance of the Q-2D PPDs was further demonstrated in image sensing and indirect X-ray detection, showcasing their potential for versatile optoelectronic applications.

Ultrasensitive photodetectors with high responsivity, rapid response speed, and low dark current are in urgent demand for a wide range of applications. The coupling between plasmonic metals and heterojunctions can enhance light absorption capabilities and facilitate hot electrons injection. However, recent research on plasmonic heterojunction devices has primarily focused on enhancing the local electromagnetic field, while the practical use of hot electrons remains limited. This is due to the formation of defects when metal nanoparticles (NPs) are integrated onto the surface of heterojunctions. Energetic hot electrons and photogenerated carriers are trapped by defect states, resulting in prolonged carrier lifetimes. The excited-state carriers cannot be effectively utilized, which reduces the photoelectric conversion efficiency of the devices. In this study, we propose a Cu@CuO core–shell plasmonic structure designed for ultrasensitive photodetection. The presence of the CuO layer effectively reduces defects and establishes a Type-II band alignment for the device, thereby enhancing hot electrons injection efficiency and charge transfer. The MoS2/Cu@CuO photodetector exhibits a high responsivity (633 A/W) without sacrificing the response speed (28 ns). The core–shell architecture of metal NPs provides a viable strategy for further development of ultrasensitive photodetectors utilizing hot electrons injection.

The electrochemical water splitting process is fundamentally constrained by sluggish intrinsic reaction kinetics and low energy conversion efficiency. Developing highly efficient bifunctional electrocatalysts is crucial for enhancing electrocatalytic reaction kinetics and improving electron transfer efficiency. Herein, we fabricated the nanocage-like Fe-doped CoS2 interwoven with carbon nanotubes (FCS/CNT) as a bifunctional electrocatalyst. The nanocage architecture imparts a high surface area, thereby augmenting the number of electrochemically active sites. The incorporation of carbon nanotubes (CNTs) mitigates CoS2 agglomeration and enhances the electrical conductivity, thereby amplifying the charge transfer efficiency. Doping with Fe lowers the adsorption energy of intermediates, thereby enhancing electrocatalytic performance. Crucially, the CoS2 phase undergoes in situ reconstruction into CoOOH during the high redox potential, which acts as highly active electrocatalytic material facilitating oxygen evolution. Through optimizing CNT concentration, this FCS/CNT configuration exhibits remarkable HER activity (η10 = 143 mV) and an excellent OER performance (η10 = 265 mV). Furthermore, the electrocatalysts demonstrate exceptional stability, retaining 90.9% of the current density for HER and 89.0% for OER after 36,000 s of continuous operation. This approach underscores the design of high-performance electrocatalysts through strategic structural engineering, heteroatom doping, and carbon incorporation, resulting in outstanding hydrogen and oxygen evolution activity.

We developed energy-efficient membrane III-V distributed-reflector lasers on silicon-based substrates for ultrafast short-reach communication links and neuromorphic computing applications.By leveraging high-speed photon-photon interactions enabled by integrated optical feedback and a high-opticalconfinement membrane structure, we demonstrated record-fast directly modulated laser bandwidths and spike-processing rates with ultralow operating energies.This is a step towards our goal of reducing the carbon footprint of information and communication technology and artificial intelligence hardware, while keeping pace with the increasing demand of processing speeds.

In this work, we study a 1D silicon photonic formed by a set of silicon nanobricks, which supports a Bragg photonic bandgap (PBG) for TE-like polarization. We show that the Bragg PBG can vanish because of the interplay between the electric and magnetic dipole of its constituent silicon nanobricks.

A fast volatile amplitude switching response is demonstrated in a 1-μm-long GST/Si waveguides. More than 10⁷ cycles are performed with switching energies of 200 pJ and turn-off times as low as 25 ns.

Nanolight sources employing III-V GaAs semiconductor materials as the gain medium are crucial for the fabrication of miniaturized optical sources such as nanoLEDs and nanolasers with emerging applications in 3D sensing, optical data communication, spectroscopy, medical diagnosis and even neuromorphic computing [1] . However, the surfaces of GaAs-based compounds and their interfaces with dielectrics tend to host large densities of electronically active defects. Particularly, when the devices are scaled to the deep subwavelength size (<<1 µm), a substantial increase of the nonradiative recombination at room-temperature leads to low-efficient nanolight sources and respective ultrashort lifetimes of ~100 ps, typically orders of magnitude smaller than the bulk material [2] . Recently, it has been suggested that passivation of GaAs with silicon nitride (SiN x ) can improve the electrical performance of GaAs [3] , but its impact in optical nanodevices remains almost unexplored.

Low-power dissipation lasers on Si are needed for short-distance optical interconnects. We review our recent progress on semiconductor lasers ranging from 100-μm long to wavelength-scale cavities. Strong optical confinement and gratings with a large coupling coefficient are the key to attaining ultralow power consumption lasers.

We present theoretically the formation of exciton–photon polaritons and exciton-surface plasmon polaritons in a perovskite-based subwavelength lattice on the metallic plane. It is shown that the later polaritons will be achieved as the perovskite layer is ultra-thin ( &lt; 50 nm ), while the co-existence of both polaritons will dominate, as the thickness of the perovskite metasurface approaches wavelength-scale. In the two cases, the lower polaritonic branches consist of dark and bright modes corresponding to infinite and finite radiative quality factors, respectively. Another salient property in this work is that it allows one to obtain exceptional points (EPs) in momentum space with a four-fold enhancement of local density of states through engineering the perovskite metasurface. Our findings show that the perovskite metasurface is an attractive and rich platform to make polaritonic devices, even with the presence of a lossy metallic layer.