Yiming Yang

The development of polarization-sensitive photodetectors based on low-dimensional materials with intrinsic lattice anisotropy has paved the way for next-generation polarizer-free and integration-friendly polarization-sensitive optoelectronic devices. Despite their superiority in miniaturization, the relatively low dichroic ratios (DRs) hinder further industrialization. In this work, low-dimensional derivatives of perovskite, quasi-1D yellow-phase (δ-phase) CsPbI3 single nanowires (NWs) are investigated for polarization-sensitive photodetection. Aberration-corrected transmission electron microscopy (TEM) and angle-resolved polarized Raman spectroscopy (ARPRS) reveal the pronounced crystallographic anisotropy of δ-CsPbI3. The pristine δ-CsPbI3 single NW photodetector exhibits a large DR of up to 8.3 under 405 nm illumination. To overcome the limited optoelectronic performance arising from the indirect bandgap nature of δ-CsPbI3, localized surface plasmon resonance (LSPR) is introduced by decorating the δ-CsPbI3 single NW with Au nanoparticles (NPs) via thermal evaporation. The Au-decorated device exhibits up to approximately 9-fold photocurrent enhancement compared with the pristine one, achieving a photoresponsivity (R) of 5.3 mA W–1 and a specific detectivity (D*) of 1.1 × 1010 Jones while retaining the high polarization sensitivity. In addition, the Au-decorated device demonstrates appreciable operational stability under ambient conditions, preserving 92% of its initial photocurrent after 400 switching cycles. This work unveils the great potential of the δ-CsPbI3 single NW for polarized light detection and demonstrates the feasibility of Au NP decoration regarding optoelectronic performance optimization, which can potentially be extended to other low-dimensional perovskite derivatives with analogous quasi-1D chain lattices.

Mid‐ and long‐wavelength infrared photodetectors based on conventional narrow‐bandgap materials often suffer from high dark currents at room temperature due to their inherent material properties, limiting their performance. Here, a pBn ⁺ unipolar barrier infrared photodetector with epitaxial PbSe/CdSe/Bi ₂ Se ₃ architecture was proposed, which could effectively suppress dark current and enable superior room temperature operation. By integrating a wide‐bandgap CdSe barrier layer between PbSe and Bi ₂ Se ₃ pn heterojunction, the barrier device achieves significant dark current reduction, reaching 66.1 mA/cm ² at room temperature. Additionally, the barrier detector exhibits a strong infrared photoresponse with a responsivity of 0.59 A/W and a detectivity of 2.29 × 10 ⁹ cm·Hz ^1/2 ·W ⁻¹ under 2.7 µm illumination. Based on its compact design, lightweight structure, and excellent performance at room temperature, the proposed pBn ⁺ PbSe‐based barrier photodetector holds great promise for both military and civilian infrared applications.

Minimizing contact resistance between metal electrodes and perovskites remains a critical challenge in developing perovskite‐based electronic and optoelectronic devices. Despite extensive experimental and theoretical efforts to minimize the contact resistance, atomic‐level insights into metal‐perovskite interfaces remain insufficiently understood. In this paper, we investigate the electronic and transport properties of 2D hybrid organic–inorganic perovskites, specifically (BA) ₂ PbBr ₄ and (PEA) ₂ PbBr ₄ , which consist of monolayer bromide perovskite layers with different organic spacer molecules: n‐butylammonium (BA) and phenylethylammonium (PEA) cations. We provide a comprehensive analysis of the Au/perovskites interface, considering two contact configurations, i.e., top‐contact and edge‐contact. We perform first‐principles calculations and use the nonequilibrium Green's function formalism to calculate the transport characteristics. We find that a Schottky barrier forms in the top‐contact configuration, but the edge‐contact configuration shows ohmic behavior for both Au/(BA) ₂ PbBr ₄ and Au/(PEA) ₂ PbBr ₄ . The edge‐contact configuration also enables highly efficient charge injection with a negligible interfacial tunneling barrier due to Au‐induced midgap states. For the top contact configuration, Au/(PEA) ₂ PbBr ₄ shows better transport behavior compared to (BA) ₂ PbBr ₄ , which is attributed to its lower tunneling barrier and higher density of metal‐induced midgap states. This work provides theoretical guidelines for designing low‐resistance metal‐2D hybrid perovskite contacts.

Limitations in heteroepitaxial growth and material property modulation present a formidable challenge for the development of near-infrared-midwave infrared (NIR-MIR) dual-band uncooled detectors capable of operating in both quantum communication and thermal analysis applications. Leveraging our proposed substrate surface selenization technique, we demonstrate a PbSe/Ge/Si heterostructure enabling response at NIR and MIR. The device achieves a room-temperature responsivity of 0.43 A·W^-1 at 2700 nm and 0.7 A·W^-1 at 1550 nm under laser illumination. Blackbody testing reveals peak detectivities (D*) of 4.2 × 10⁹ cm·Hz^1/2·W^-1 at 3.7 μm and 3.5 × 10⁹ cm·Hz^1/2·W^-1 at 1.2 μm. Additionally, the theoretically optimized structure shows that a back-to-back n-i-p-i-n architecture could elevate D* to 2.0 × 10¹⁰ cm·Hz^1/2·W^-1 and 9.8 × 10¹⁰ cm·Hz^1/2·W^-1 at MIR and NIR, respectively. This architecture represents a promising step toward compact multispectral systems with room-temperature dual-band sensitivity, which are of interest for field-deployable quantum communication terminals and portable thermal analytics.

Minimizing the footprint of individual cells in a memristor array is crucial for increasing packing density, reducing power consumption and boosting computational performance. However, the downscaling of memristive devices incorporating halide perovskites has been challenging due to the polycrystalline nature of the active layer. In this work, we employed monocrystalline nanoplates of the all‐inorganic perovskite CsPbBr ₃ , and combined nanofabrication and conductive atomic force microscopy to progressively downsize the memristors to the micrometer and nanometer scale. We report an ion crowding effect in these micro‐ and nano‐ devices with unilaterally downscaled electrodes. The ion crowding effect is analogous to the current crowding effect in bipolar junction transistors, and originates from the substantially enhanced electric field in the peripheral of downsized electrodes. This effect fundamentally alters the microscopic ionic transport and distribution, leading to distinct switching behaviors and morphological deformation including protrusions and indentations. Further downsizing the critical dimension of memristors to 30 nm intensifies the crowding effect, resulting in anisotropic switching characteristics and unique “hole‐in‐a‐bump” surface feature. This study offers insight into the field‐induced ionic behaviors at microscale, and lays the groundwork for miniaturized perovskite memristors.

Thermal transport at the microscopic level is intuitively considered as a fast and random process. However, here the formation of significant microscale thermal inhomogeneity in single nanowires (NWs) of halide perovskites is reported, where the temperature gradient can be further converted to a compositional gradient via bandgap engineering. Upon employing a heat source or heat sink in the setup, arrays of composition‐graded NWs are fabricated by anion‐exchange with halogen‐containing vapor. Quantitative analysis from multiple spatial‐resolved scanning probe characterizations suggests that the exchange reaction occurs globally with a monotonically decreased rate along individual NWs, and the corresponding thermal simulation reveals a prominent temperature gradient up to 3.6 °C µm ⁻¹ in the axial direction. The large thermal inhomogeneity is attributed to the ultra‐low thermal conductivity of perovskites combined with reduced nanowire (NW) diameter. In addition, the gradient NWs exhibit excellent optoelectronic features suitable for further integration into functional devices. This work provides guidelines for the composition manipulation of perovskites through phononic engineering, extending their applications in ultracompact microspectrometers, spectral imaging sensors, and other miniaturized optoelectronic devices.

One-dimensional semiconductor nanowires (NWs) are natural polarization photodetectors, thanks to their optical absorption anisotropy and efficient electrical transport channels. However, ultrathin NWs beyond practical fabrication capabilities are often required to achieve the desired polarization sensitivity. Here, we demonstrate a configuration of planar arrayed core-shell NW architectures with substantially enhanced absorption dichroism for linearly polarized light. The high polarization ratio originates from synergistic effect of three rational designs: a NW core consisting of indirect-bandgap semiconductor as light-trapping cavity, a thin shell of photosensitive material as light absorber, and arrayed photonic structure for optical interference. By employing all-inorganic halide perovskites, these NW arrays exhibit a dichroic ratio up to 110.5 without the need for ultrathin NWs. The core-shell NW architecture is experimentally feasible and offers insights into design of high-sensitivity polarization photodetectors using optical resonance.