Low-Dimensional-Materials-Based Photodetectors for Next-Generation Polarized Detection and Imaging

Development and challenges of polarization-sensitive photodetectors based on 2D materials

Polarization-sensitive photodetectors based on two-dimensional (2D) materials have garnered significant research attention owing to their distinctive architectures and exceptional photophysical properties. Specifically, anisotropic 2D materials, including semiconductors such as black phosphorus (BP), tellurium (Te), transition metal dichalcogenides (TMDs), and tantalum nickel pentaselenide (Ta2NiSe5), as well as semimetals like 1T'-MoTe2 and PdSe2, and their diverse van der Waals (vdW) heterojunctions, exhibit broad detection spectral ranges and possess inherent functional advantages. To date, numerous polarization-sensitive photodetectors based on 2D materials have been documented. This review initially provides a concise overview of the detection mechanisms and performance metrics of 2D polarization-sensitive photodetectors, which are pivotal for assessing their photodetection capabilities. It then examines the latest advancements in polarization-sensitive photodetectors based on individual 2D materials, 2D vdW heterojunctions, nanoantenna/electrode engineering, and structural strain integrated with 2D structures, encompassing a range of devices from the ultraviolet to infrared bands. However, several challenges persist in developing more comprehensive and functional 2D polarization-sensitive photodetectors. Further research in this area is essential. Ultimately, this review offers insights into the current limitations and challenges in the field and presents general recommendations to propel advancements and guide the progress of 2D polarization-sensitive photodetectors.

Rotation-Symmetry Grating Contact Photodetector for Visible Full Linear Polarimetry Detection

Integrated linearly polarized (LP) light detectors hold importance for next-generation optoelectronic systems. However, current compact LP photodetectors relying on the scalar anisotropic absorption of natural materials or the bipolar polarization photoresponse of artificial structures are usually unable to achieve full polarization angle detection or are restricted to the long-infrared waveband. Here, we report a photodetector by integrating InSe flakes with three-fold rotation-symmetry grating contacts for zero-bias full linear polarimetry detection. The photodetector creates an asymmetric junction interface driven by the polarization-dependent propagating surface plasmon polariton wave, generating a zero-bias bipolar polarization photoresponse. By direct measurement of the photocurrents, linear polarization angle and incident power intensity detection can be achieved in a single device at 633 nm. Moreover, we demonstrate the decoding of polarization-angle-encrypted information, showing the great potential of the proposed devices in polarization information processing. Our work offers a promising strategy for developing compact full linear polarimetry photodetectors.

Simultaneous AoLP and DoLP Detection in a Bias-Switchable PdSe2/MoS2/PdSe2 Heterojunction for Polarization Discrimination

On-chip polarized photodetectors play a crucial role in advancing ultra-compact optoelectronic devices for next-generation technologies. However, simultaneously detecting the angle of linear polarization (AoLP) and the degree of linear polarization (DoLP) within a single device remains a challenging task, particularly due to the inherently weak polarization states found in naturally anisotropic materials. In this paper, it is reported on the development of a twisted monopole barrier photodetector based on a PdSe2/MoS2/PdSe2 configuration. This photodetector features a rapid response time of 7-12 µs. In an imaging demonstration, it operates as a single-polarization photodetector, reconstructing AoLP and DoLP distributions of target objects through bias-switchable polarization detection across a wide spectral range, all without the plasmonic/metasurface nanostructures or polarization filters. Additionally, it demonstrates bipolar characteristics under zero-bias conditions at room temperature, enabling dual-binary coding for polarimetric-encoded communication. These combination of features positions the photodetector as a highly promising candidate for on-chip applications.

Modulation anisotropy of nanomaterials toward monolithic integrated polarization-sensitive photodetectors

By virtue of the unique ability of providing additional information beyond light intensity and spectra, polarization-sensitive photodetectors could precisely identify targets in several concealed, camouflaged, and non-cooperative backgrounds, making them highly suitable for potential applications in remote sensing, astronomical detection, medical diagnosis, etc. Therefore, to provide a comprehensive design guideline for a wide range of interdisciplinary researchers, this review provides a general overview of state-of-the-art linear, circular, and full-Stokes polarization-sensitive photodetectors. In particular, from the perspectives of technological progress and the development of nanoscience, the detailed discussion focuses on strategies to simplify high-performance polarization-sensitive photodetectors, reducing their size and achieving a smaller volume. In addition, to lay a solid foundation for modulating the properties of future nanostructure-based polarization-sensitive photodetectors, insights into light-matter interactions in low-symmetry materials and asymmetric structures are provided here. Meanwhile, the corresponding opportunities and challenges in this research field are identified.

Anchored epitaxial growth of single-oriented one-dimensional organic nanowires towards their integration into field-effect transistors and polarization-sensitive photodetector arrays

The deliberate assembly of organic small molecules into single-oriented one-dimensional (1D) nanowires is essential for the large-scale, on-chip integration of organic nanowire-based (opto)electronic devices. However, achieving single-oriented 1D organic nanowires remains a considerable challenge, predominantly attributed to the intricate nucleation and growth behaviors of the molecules. Herein, an anchored epitaxial growth method was developed to facilitate the single-oriented growth of 1D organic nanowires using the parallel nanogrooves on the annealed sapphire as anchoring seed crystal templates. The depth of the nanogrooves was greater than the length of the molecules, enabling the molecules to be embedded into the V-shaped nanogrooves and to form anchored nuclei during the physical vapor deposition process. Subsequently, these nuclei exhibited directional epitaxial growth along the nanogrooves, resulting in the formation of single-oriented 1D organic nanowires. Various organic small molecule 1D nanowires with uniform molecular packing and orientation were obtained and utilized for subsequent device integration. 2,7-Dioctyl[1]benzothiophene (C8-BTBT) was used as a model material, and the flexible organic field-effect transistor (OFET) based on the single C8-BTBT nanowire exhibited a mobility of up to 1.5 cm2 V-1 s-1. Benefiting from high mobility and uniform orientation, the integrated polarization-sensitive photodetector arrays based on 1D C8-BTBT nanowires exhibited a high dichroic ratio of up to 2.83, which was higher than those of some previously investigated 1D nanowires and two-dimensional materials. This work presents new opportunities to fabricate single-oriented 1D organic nanowires for integrated devices.

Ferroelectric Tunable Nonvolatile Polarization Detection Based on 2H α-In2Se3

The development of polarization photodetectors utilizing two-dimensional materials holds significant promise due to their distinctive properties and potential for high integration. However, a major limitation of most current polarization photodetectors is their lack of polarization tuning capability, which restricts the versatility of individual devices. In this study, a nonvolatile ferroelectric tunable polarization photodetector is explored based on 2H α-In2Se3. The ferroelectric semiconductor field-effect transistor (FeS-FET) based on 2H α-In2Se3 were fabricated, demonstrating an on/off ratio of 103. Ferroelectric modulation photoelectric response was explored under 650 nm illumination, the device achieves a maximum optical responsivity of 75 A/W, with a detectivity of 1.46 × 1010 jones. Notably, in the context of polarized light detection, the device's polarization sensitivity experiences significant modulation due to ferroelectric polarization switching. The dichroic ratios can be tuned to 1.74 and 3 for polarization down and up states, respectively. Moreover, by adjusting the degree of ferroelectric polarization switching, the dichroic ratio can be linearly tuned. The polarization up state can continuously enhance the dichroic ratio in the range of 2.71-3.11, while the polarization down state can continuously weaken the dichroic ratio in the range of 2.54-2.06. This research not only advances the understanding of 2H α-In2Se3 in polarization detection but also introduces a nonvolatile ferroelectric modulation approach for tunable polarization detection.

2D Perovskite Heterojunction-Based Self-Powered Polarized Photodetectors with Controllable Polarization Ratio Enabled by Ferro-Pyro-Phototronic Effect

Metal halide perovskites (MHPs) are commonly used in polarization-sensitive photodetectors (PDs) for applications such as polarization imaging, remote sensing, and optical communication. Although various methods exist to adjust the polarization-sensitive photocurrent, a universal and effective approach for continuous control of MHPs' optoelectronic and polarized properties is lacking. A universal strategy to electrically modulate the polarization ratio (PR) of self-powered polarized PDs using the ferro-pyro-phototronic effect (FPPE) in 2D perovskites is presented. By varying the amplitude and direction of ferroelectric polarization voltage, the built-in electric field in the heterojunction can be modulated, allowing for controllable PR regulation and adjustable polarization characteristics. Moreover, the polarized pyroelectric photoresponses are realized, significantly enhancing the responsivity, response speed of the polarized PDs. Both the pyroelectric currents and photocurrents exhibit obvious polarization characteristics. This method's versatility is demonstrated by creating three additional quasi-2D MHP ferroelectric-based polarized-sensitive PDs. A proof-of-concept for encrypted optical communication is achieved using the UV-sensitive PDs as light-sensing units. These findings highlight FPPE's potential to enhance ferroelectric device polarization control, enabling high-performance and self-powered polarization photodetection.

2D AgTiPS6: a Cross-Stacked In-Plane Anisotropic Semiconductor for Broadband and Polarization-Sensitive Photodetection

2D anisotropic materials, typically consisting of 1D distorted chains arranged in parallel or anti-parallel patterns, are gaining attention for their potential in anisotropic electronic and optoelectronic devices. 2D anisotropic materials with cross-stacked interconnected 1D chains will show improved anisotropy and stability. Nonetheless, to date, no 2D anisotropic materials featuring cross-stacked motifs have been experimentally realized. This work identifies AgTiPS6 atomic layers, the 2D in-plane anisotropic material with cross-stacked structural motifs, as an n-type semiconductor with a 1.0 eV band gap. Significantly, the unique cross-stacked configuration of 2D AgTiPS6 results in a significant in-plane anisotropy, with electrical and optoelectrical anisotropies measuring 5.44 and 2.44, respectively, as well as an axially orientation selectivity. Meanwhile, a broadband response from visible (Vis, 405 nm) to middle infrared (MIR, 10.6 µm) is achieved in the AgTiPS6-based photodetector, with the photoresponse above the bandgap attributed to photothermoelectric effect. Furthermore, 2D AgTiPS6 has demonstrated environmental stability exceeding 12 months and a laser damage threshold exceeding 10 W cm- 2, attributed to its extra-thick monolayer (1.32 nm). This work introduces a novel in-plane anisotropic material, expanding the repertoire of 2D anisotropic materials and offering potential for the development of anisotropic electronic and optoelectronic devices.

Lensless Polarimetric Imaging and Encryption Enabled by Te/ReSe2 van der Waals Heterostructure Polarization-Sensitive Photodetector

Polarimetric imaging and encryption improve target recognition precision and information security, enhancing image sensors' perceptual acuity and interference resilience. However, the miniaturization of sensing systems faces challenges due to the complex integration of dispersive optical components such as polarizers. To address this, we propose a polarization-sensitive photodetector using a Te/ReSe2 van der Waals heterostructure. This design leverages type-II band alignment for efficient photocarrier segregation. The anisotropic crystal orientations of ReSe2 and Te layers integrate photon absorption with photocarrier extraction, boosting the functionality. The Te/ReSe2 device offers a broad spectral photoresponse (300-965 nm), a high polarization ratio of 8.9, and a fast response time of 55.4/55.7 μs at 635 nm. These properties enable high-resolution polarimetric imaging and precise image processing. This study provides a blueprint for developing miniaturized polarization-sensitive photodetectors and advancing lensless polarimetric optoelectronics.

Navigating the transitional window for organic semiconductor single crystals towards practical integration: from materials, crystallization, and technologies to real-world applications

Organic semiconductor single crystals (OSSCs), which possess the inherent merits of long-range order, low defect density, high mobility, structural tunability and good flexibility, have garnered significant attention in the organic optoelectronic community. Past decades have witnessed the explosive growth of OSSCs. Despite numerous conceptual demonstrations, OSSCs remain in the early stages of implementation for applications that require high integration and multifunctionality. The commercialization trend of organic optoelectronic devices is driving the development of highly integrated OSSCs. Therefore, timely tracking of material requirements, crystallization demands, and key technologies for high integration, along with exploring their limitations and potential pathways, will provide critical guidance during this pivotal transition period. From the perspective of materials properties, multifunctional materials, such as ambipolar charge transport materials, high mobility emission materials and others, aiming at high integration, deserve our attention, and the material design rules are carefully discussed in the first section. Following this, we delve into the controllable growth of large-scale OSSCs based on crystallization thermodynamics and kinetics. Key technologies for achieving high integration are then discussed, with an emphasis on methods for growing wafer-scale organic single crystals and patterning single crystalline arrays. Subsequently, we outline the cutting-edge optoelectronic applications based on OSSCs, including organic logic circuits, electroluminescent displays, and image sensors. Moreover, explicitly recognizing as yet limitations and prospects on the road to 'lab-to-fab' transitions for OSSCs is crucial. Thus, we conclude by offering an objective assessment of key limitations and potential, encompassing aspects such as uniformity, integration density, stability, and driving capability, providing an instructive projection for future advancements.

Optoelectronic metadevices

Metasurfaces have introduced new opportunities in photonic design by offering unprecedented, nanoscale control over optical wavefronts. These artificially structured layers have largely been used to passively manipulate the flow of light by controlling its phase, amplitude, and polarization. However, they can also dynamically modulate these quantities and manipulate fundamental light absorption and emission processes. These valuable traits can extend their application domain to chipscale optoelectronics and conceptually new optical sources, displays, spatial light modulators, photodetectors, solar cells, and imaging systems. New opportunities and challenges have also emerged in the materials and device integration with existing technologies. This Review aims to consolidate the current research landscape and provide perspectives on metasurface capabilities specific to optoelectronic devices, giving new direction to future research and development efforts in academia and industry.

Low-Symmetry Van der Waals Dielectric GaInS3 Triggered 2D MoS2 Giant Anisotropy via Symmetry Engineering

Low-symmetry structures in van der Waals materials have facilitated the advancement of anisotropic electronic and optoelectronic devices. However, the intrinsic low symmetry structure exhibits a small adjustable anisotropy ratio (1-10), which hinders its further assembly and processing into high-performance devices. Here, a novel 2D anisotropic dielectric, GaInS3 (GIS), which induces isotropic MoS2 to exhibit significant anisotropic optical and electrical responses is demonstrated. With the excellent gate modulation ability of 2D GIS (dielectric constant k ∼12), MoS2 field effect transistor (FET) shows an adjustable conductance ratio from isotropic to anisotropic under dual-gate modulation, up to 106. Theoretical calculations indicate that anisotropy originates from lattice mismatch-induced charge density deformation at the interface. Moreover, the MoS2/GIS photodetector demonstrates high responsivity (≈4750 A W-1) and a large dichroic ratio (≈167). The anisotropic van der Waals dielectric GIS paves the way for the development of 2D transition metal dichalcogenides (TMDCs) in the fields of anisotropic photonics, electronics, and optoelectronics.

Low-Symmetry 2D t-InTe for Polarization-Sensitive UV-Vis-NIR Photodetection

Polarization-sensitive photodetection grounded on low-symmetry 2D materials has immense potential in improving detection accuracy, realizing intelligent detection, and enabling multidimensional visual perception, which has promising application prospects in bio-identification, optical communications, near-infrared imaging, radar, military, and security. However, the majority of the reported polarized photodetection are limited by UV-vis response range and low anisotropic photoresponsivity factor, limiting the achievement of high-performance anisotropic photodetection. Herein, 2D t-InTe crystal is introduced into anisotropic systems and developed to realize broadband-response and high-anisotropy-ratio polarized photodetection. Stemming from its narrow band gap and intrinsic low-symmetry lattice characteristic, 2D t-InTe-based photodetector exhibits a UV-vis-NIR broadband photoresponse and significant photoresponsivity anisotropy behavior, with an exceptional in-plane anisotropic factor of 1.81@808 nm laser, surpassing the performance of most reported 2D counterparts. This work expounds the anisotropic structure-activity relationship of 2D t-InTe crystal, and identifies 2D t-InTe as a prospective candidate for high-performance polarization-sensitive optoelectronics, laying the foundation for future multifunctional device applications.

Dual-Electrically Configurable MoTe2/In2S3 Phototransistor toward Multifunctional Applications

Photodetectors, essential for a wide range of optoelectronic applications in both military and civilian sectors, face challenges in balancing responsivity, detectivity, and response time due to their inherent unidirectional carrier transport mechanism. Multifunctional photodetectors that address these trade-offs are highly sought after for their potential to reduce costs, simplify system design, and surpass Moore's Law limitations. Herein, we present a multimodal phototransistor based on a 2D MoTe2/In2S3 heterostructure. Through dual electrical modulation employing bias voltage and gate voltage, we engineer the energy band to achieve switchable photoresponse mechanisms between photoconductive and photovoltaic modes. In photoconductive mode, the device exhibits a responsivity of 320 A/W and a specific detectivity of 1.2 × 1013 Jones. Meanwhile, in photovoltaic mode, it exhibits a light on/off ratio of 2 × 105 and response speed of 0.68/0.60 ms. These capabilities enable multifunctional applications such as high-resolution imaging across various wavelengths, a conceptual optoelectronic logic gate, and dual-channel optical communication. This work makes an advancement in the development of future multifunctional optoelectronic devices.

Optoelectronic Devices for In-Sensor Computing

The demand for accurate perception of the physical world leads to a dramatic increase in sensory nodes. However, the transmission of massive and unstructured sensory data from sensors to computing units poses great challenges in terms of power-efficiency, transmission bandwidth, data storage, time latency, and security. To efficiently process massive sensory data, it is crucial to achieve data compression and structuring at the sensory terminals. In-sensor computing integrates perception, memory, and processing functions within sensors, enabling sensory terminals to perform data compression and data structuring. Here, vision sensors are adopted as an example and discuss the functions of electronic, optical, and optoelectronic hardware for visual processing. Particularly, hardware implementations of optoelectronic devices for in-sensor visual processing that can compress and structure multidimensional vision information are examined. The underlying resistive switching mechanisms of volatile/nonvolatile optoelectronic devices and their processing operations are explored. Finally, a perspective on the future development of optoelectronic devices for in-sensor computing is provided.

Bulk Photovoltaic Effect in Polar 3D Perovskitoid Enables Self-Powered Polarization-Sensitive Photodetection

The family of polar hybrid perovskites, in which bulk photovoltaic effects (BPVEs) drive steady photocurrent without bias voltage, have shown promising potentials in self-powered polarization-sensitive photodetection. However, reports of BPVEs in 3D perovskites remain scare, being mainly hindered by the limited dipole moment or lack of symmetry breaking. Herein, a polar 3D perovskitoid, (BDA)Pb2Br6 (BDA = NH3C4H8NH3), where the spontaneous polarization (Ps)-induced BPVE drives self-powered photodetection of polarized-light is reported. Emphatically, the edge-sharing Pb2Br10 dimer building unit allows the optical anisotropy and polarity in 3D (BDA)Pb2Br6, which triggers distinct optical absorption dichroism ratio of ≈2.80 and BPVE dictated photocurrent of 3.5 µA cm-2. Strikingly, these merits contribute to a polarization-sensitive photodetection with a high polarization ratio (≈4) under self-powered mode, beyond those of 2D hybrid perovskites and inorganic materials. This study highlights the potential of polar 3D perovskitoids toward intelligent optoelectronic applications.

Realization of High-Performance Self-Powered Polarized Photodetection with Large Temperature Window in a 2D Polar Perovskite

Polarization photodetection taking advantage of the anisotropy of 2D materials shines brilliantly in optoelectronic fields owing to differentiating optical information. However, the previously reported polarization detections are mostly dependent on external power sources, which is not conducive to device integration and energy conservation. Herein, a 2D polar perovskite (CBA)2CsPb2Br7 (CCPB, CBA = 4-chlorobenzyllamine) has been successfully synthesized, which shows anticipated bulk photovoltaic effect (BPVE) with an open-circuited photovoltage up to ≈0.2 V. Devices based on CCPB monomorph fulfill a fascinating self-powered polarized photodetection with a large polarization ratio of 2.7 at room temperature. Moreover, CCPB features a high phase-transition temperature (≈475 K) which prompts such self-powered polarized photodetection in a large temperature window of device operation, since BPVE generated by spontaneous polarization can only exist in the polar structure prior to the phase transition. Further computational investigation reveals the introduction of CBA+ with a large dipole moment contributes to quite large polarization (17.5 µC cm-2) and further super high phase transition temperature of CCPB. This study will promote the application of 2D perovskite materials for self-powered polarized photodetection in high-temperature conditions.

Template-Confined Oriented Perovskite Nanowire Arrays Enable Polarization Detection and Imaging

Polarized light detection can effectively identify the difference between the polarization information on the target and the background, which is of great significance for detection in complex natural environments and/or extreme weather. Generally, polarized light detection inevitably relies on anisotropic structures of photodetector devices, while organic-inorganic hybrid perovskites are ideal for anisotropic patterning due to their simple and efficient preparation by solution method. Compared to patterned thin films, patterned arrays of aligned one-dimensional (1D) perovskite nanowires (PNWAs) have fewer grain boundaries and lower defect densities, making them well suited for high-performance polarization-sensitive photodetectors. Here, we fabricated PNWAs crystallographically aligned with variable line widths and alignment densities employing CD-ROM and DVD-ROM grating pattern template-confined growth (TCG) methods. The photodetectors constructed from MAPbI3 PNWAs achieved responsivity of 35.01 A/W, detectivity of 6.85 × 1013 Jones, and fast response with a rise time of 172 μs and fall time of 114 μs. They were successfully applied to high-performance polarization detection with a polarization ratio of 1.81, potentially applicable in polarized light detection systems.

Toward the Production of Super Graphene

The quality requirements of graphene depend on the applications. Some have a high tolerance for graphene quality and even require some defects, while others require graphene as perfect as possible to achieve good performance. So far, synthesis of large-area graphene films by chemical vapor deposition of carbon precursors on metal substrates, especially on Cu, remains the main way to produce high-quality graphene, which has been significantly developed in the past 15 years. However, although many prototypes are demonstrated, their performance is still more or less far from the theoretical property limit of graphene. This review focuses on how to make super graphene, namely graphene with a perfect structure and free of contaminations. More specially, this study focuses on graphene synthesis on Cu substrates. Typical defects in graphene are first discussed together with the formation mechanisms and how they are characterized normally, followed with a brief review of graphene properties and the effects of defects. Then, the synthesis progress of super graphene from the aspects of substrate, grain size, wrinkles, contamination, adlayers, and point defects are reviewed. Graphene transfer is briefly discussed as well. Finally, the challenges to make super graphene are discussed and a strategy is proposed.

Symmetry-Reduction Enhanced Polarization-Sensitive Photoresponse Based on One-Dimensional van der Waals Materials

Designing high-performance polarization-sensitive photodetectors is essential for photonic device applications. Anisotropic one-dimensional (1D) van der Waals (vdW) materials have provided a promising platform to that end. Despite significant advances in 1D vdW photonic devices, their performance is still far from delivering practical potential. Herein, we propose the design of high-performance polarization-sensitive photodetectors using unique 1D vdW materials. By leveraging the chemical vapor transport technique, we successfully fabricate high-quality 1D vdW Nb2Pd1-xSe5 (x = 0.29) nanowires. The 1D vdW Nb2Pd1-xSe5 photodetector exhibits a high mobility of ∼56 cm2/(V s) and superior photoresponse performance, including a high responsivity of 1A/W and an ultrafast response time of ∼8 μs under 638 nm illumination. Moreover, the 1D vdW Nb2Pd1-xSe5 photodetector demonstrates excellent polarization-sensitive photoresponse with a degree of linear polarization (DOLP) up to 0.85 and can be modulated by adjusting the gate voltage, laser power density, and wavelength. Those exceptional performance are believed to be relevant to the symmetry-reduction induced by the partial occupation of Pd sites. This study offers feasible approaches to enhance the anisotropy of 1D vdW materials and the modulation of their polarization-sensitive photoresponse, which may provide deep insights into the physical origin of anisotropic properties of 1D vdW materials.

Towards high-performance polarimeters with large-area uniform chiral shells: a comparative study on the polarization detection precision enabled by the Mueller matrix and deep learning algorithm

Polarization detection and imaging technologies have attracted significant attention for their extensive applications in remote sensing, biological diagnosis, and beyond. However, previously reported polarimeters heavily relied on polarization-sensitive materials and pre- established mapping relationships between the Stokes parameters and detected light intensities. This dependence, along with fabrication and detection errors, severely constrain the working waveband and detection precision. In this work, we demonstrated a highly precise, stable, and broadband full-Stokes polarimeter based on large-area uniform chiral shells and a post-established mapping relationship. By precisely controlling the geometry through the deposition of Ag on a large-area microsphere monolayer with a uniform lattice, the optical chirality and anisotropy of chiral shells can reach about 0.15 (circular dichroism, CD) and 1.7, respectively. The post-established mapping relationship between the Stokes parameters and detected light intensities is established through training a deep learning algorithm (DLA) or fitting the derived mapping-relationship formula based on the Mueller matrix theory with a large dataset collected from our home-built polarization system. For the detection precision with DLA, the mean squared errors (MSEs) at 710 nm can reach 0.10% (S1), 0.41% (S2), and 0.24% (S3), while for the Mueller matrix theory, the corresponding values are 0.14% (S1), 0.46% (S2), and 0.48% (S3). The in-depth comparative studies indicate that the DLA outperforms the Mueller matrix theory in terms of detection precision and robustness, especially for weak illumination, small optical anisotropy and chirality. The averaged MSEs over a broad waveband ranging from 500 nm to 750 nm are 0.16% (S1), 0.46% (S2), and 0.61% (S3), which are significantly smaller than those derived from the Mueller matrix theory (0.45% (S1), 1% (S2), and 39.8% (S3)). The optical properties of chiral shells, the theory and DLA enabled mapping-relationships, the combination modes of chiral shells, and the MSE spectra have been systematically investigated.

Polarization-Sensitive Self-Powered Schottky Photodetector with High Photovoltaic Performance Induced by Geometry-Asymmetric Contacts

Polarization-sensitive photodetectors have attracted considerable attention owing to their potential application prospects in navigation, optical switching, and communication. However, it remains challenging to develop a facile and effective strategy to simultaneously meet the demands of low power consumption, high performance, and excellent polarization sensitivity. Herein, a series of low-symmetry two-dimensional (2D) ReSe2 Schottky photodetectors with geometry-asymmetric contacts are constructed. These devices exhibit excellent photoelectrical performance and impressive polarization sensitivity in the self-powered mode owing to the difference in the Schottky barrier height induced by the asymmetric contact areas, interfacial states, and thickness difference. Particularly, an outstanding responsivity of 379 mA/W, a decent specific detectivity of 6.8 × 1011 Jones, and a high light on/off ratio (Ilight/Idark) of over 105 under 635 nm light illumination are achieved. Scanning photocurrent mapping (SPCM) measurements further confirm that the ReSe2/drain overlapped region (corresponding to the smaller contact area side) with a higher Schottky barrier height plays a dominant role in the generation of photocurrent. Furthermore, the proposed device displays impressive polarization ratios (PRs) of 3.1 and 3.6 at zero bias under 635 and 808 nm irradiation, respectively. The high-resolution single-pixel imaging capability is also demonstrated. This work reveals the great potential of the ReSe2 Schottky photodetector with geometry-asymmetric contacts for high-performance, self-powered, and polarization-sensitive photodetection.