Ultrahigh-performance photodetectors based on low-dimensional Cs2AgBiBr6/CdS heterojunction.

Lead-free double perovskite Cs2AgBiBr6 has garnered increasing attention in photoelectric applications owing to its good stability and excellent photoelectric properties. However, the poor carrier transport in Cs2AgBiBr6 thin films constraints their further application in photodetection. To overcome this issue, we have developed an innovative low-dimensional Cs2AgBiBr6/CdS heterojunction photodetector with substantially improved performance. The device achieved a high responsivity of 6.66 × 103 A/W, an outstanding specific detectivity of 2.10 × 1014 Jones, and an impressive external quantum efficiency of 1.88 × 106 %. Additionally, the on/off current ratio of the heterojunction device reached an impressive 6.18 × 107. These key parameters are significantly better than those of most previously reported Cs2AgBiBr6-based photodetectors. Furthermore, scanning photocurrent mapping and band arrangement analysis were performed to elucidate the mechanism of photocurrent generation and transport in the low-dimensional Cs2AgBiBr6/CdS heterojunction photodetectors. This study highlights the outstanding performance of Cs2AgBiBr6/CdS heterojunction and provides a simple and effective strategy for developing high-performance Cs2AgBiBr6-based photodetectors.

Oxidation-induced graded bandgap narrowing in Two-dimensional tin sulfide for high-sensitivity broadband photodetection.

Two-dimensional (2D) layered group-IV monochalcogenides with large surface-to-volume ratio and high surface activity make that their structural and optoelectronic properties are sensitive to air oxidation. Here, we report the utilization of oxidation-induced gradient doping to modulate electronic structures and optoelectronic properties of 2D group-IV monochalcogenides by using SnS nanoplates grown by physical vapor deposition as a model system. By a precise control of oxidation time and temperature, the structural transition from SnS to SnSOx could be driven by the layer-by-layer oxygen doping and intercalation. The resulting SnSOx with a graded narrowing bandgap exhibits the enhanced optical absorption and photocurrent, leading to the fabricated SnSOx photodetector with remarkable photoresponsivity and fast response speed (<64 µs) at a broadband spectrum range of 520-1550 nm. The peak responsivity (7294 A/W) and detectivity (9.54 × 109 Jones) of SnSOx device are at least two orders of magnitude larger than those of SnS photodetector. Moreover, its photodetection performance can be competed with state-of-the-art of 2D materials-based photodetectors. This work suggests that the air oxidation could be utilized as an efficient strategy to engineer the electronic and optical properties of SnS and other 2D group-IV monochalcogenides for the development of high-performance broadband photodetectors.

Improvement of Self-Driven Nanowire-Based Ultraviolet Photodetectors by Metal-Organic Frameworks for Controlling Humanoid Robots.

Self-driven photodetectors (PDs) hold significant potential for the development of new information devices, which boast the advantages of ultralow power consumption and straightforward fabrication. In this study, we have proposed and demonstrated a self-driven ultraviolet PD utilizing gallium nitride/metal-organic framework (GaN/MOF) heterojunction nanowires successfully. By introducing Gd-ETTC MOFs on the surface of GaN nanowires, the photocurrent and responsivity of the device can be improved by approximately 75% under 310 nm illumination. Furthermore, they can also be effectively enhanced under visible light illumination. Owing to the appropriate energy level alignment, Gd-ETTC MOFs can serve as both a light harvester and a hole conductor, facilitating the efficient absorption, separation, and transmission of photogenerated carriers. It has been observed that due to reduced interface resistance, MOFs can enhance the charge transport through the acceleration of charge transfer. Furthermore, the PD equipped with MOFs is capable of continuous operation for 30,000 s, a feat attributable to the exceptional stability of both GaN nanowires and Gd-ETTC MOFs. By implementation of the humanoid robot systems, the control commands from the self-driven PD can drive the humanoid robot to execute different actions. The PD-equipped autonomous feedback system of a humanoid robot enables a seamless integration of light perception with intelligent robotic actions. Therefore, the design and demonstration of GaN/MOF nanowires hold significant reference value for further enhancing the performance of PDs and broadening their applications in ultralow-power artificial intelligence systems, humanoid intelligent robots, etc.

Design of N-doped C60-σ-B-doped C60 photodetector based on resonant tunneling diode using DFT and NEGF method.

CONTEXT: Photodetectors utilizing donor/acceptor (D/A) molecules have the capacity to detect light through molecular interactions between a donor and an acceptor molecule. These devices leverage electronic or optical changes within molecules when exposed to light, resulting in observable modifications. The unique properties of photodetectors with D/A molecules make them valuable tools in various fields, including molecular electronics. This paper presents the modeling and simulation of a single-molecule photodetector based on a D/A molecule configuration. The acceptor molecule used is N-doped C60 fullerene, while the donor molecule is B-doped C60 fullerene. Initially, simulations were conducted at zero bias voltage to determine the energy and states of the bipartite molecule. Subsequently, the system's Hamiltonian was computed based on these results. The self-consistent field method (SCF) and optical self-energy coefficients were employed for modeling. Finally, the current-voltage curve of the device was derived for various input light frequencies. The simulation and modeling results demonstrated that the device exhibited negative differential resistances at bias voltages of 0.33 V, 1.58 V, and - 0.93 V, depending on the input light frequency. Furthermore, the designed device demonstrated the ability to detect and absorb waves with different frequencies. The number of current peaks in the current-voltage curve varied with by altering the number of optical modes. METHODS: The computational work was conducted using the software package of Atomistix ToolKit (ATK-2018.06) and MATLAB code. The calculations were based on the density functional theory (DFT) approach and the self-consistent field method, specifically the non-equilibrium Green function (NEGF). The exchange correlation function was investigated using the generalized gradient approximation (GGA) proposed by Perdew, Burke, and Ernzerhof (PBE). For the calculations, we employed the double-ζ plus polarization (DZP) basis set. Initially, the structures of N doped-C60-σ-B-doped-C60 molecule underwent optimization using the DFT approach implemented in the ATK package. This optimization process allowed us to extract the parameters of the molecule. Subsequently, we utilized the NEGF formalism in MATLAB software to model and simulate photodetector based on the optimized molecule. We calculated important features of the photodetector, such as photocurrent, and compared the performance of the photodetector using photons with energies of 2 and 3 eV.

Near-Infrared Polarization-Sensitive Detection by All-Si Plasmonic Hot Electron Detectors.

Polarization-sensitive optoelectronic detection has been achieved by an all-Si detector in the NIR range, based on plasmon hot electron generation/internal photoemission effect. An advanced architecture with a specially designed anisotropic metasurface was developed and structurally optimized for maximizing the internal quantum efficiency (IQE). Assisted by finite difference time domain (FDTD) simulations, the well-designed device exhibits a maximum optical absorption of 80% around 1.45 µm, corresponding to an optical discrimination ratio of 120. Optoelectronic measurements show the peak responsivity and detectivity of 51.2 mA/W and 8.05 × 1010 cm Hz1/2/W, respectively, at 1.45 µm. A high polarization photocurrent ratio of 35 nm is also achieved at 1.55 µm. Moreover, the optoelectronic response can be tuned by a back-gate bias. Last but not least, we built up a model for theoretically estimating the IQE, which provides instructive guidance for further enhancing the optoelectronic performance of hot electron detectors.

Silver Telluride Colloidal Quantum Dot Solid for Fast Extended Shortwave Infrared Photodetector.

Extended shortwave infrared (eSWIR) photodetectors that employ solution-processable semiconductors have attracted attention for use in applications such as ranging, night vision, and gas detection. Colloidal quantum dots (CQDs) are promising materials with facile bandgap tunability across the visible-to-mid-infrared wavelengths. However, toxic elements, such as Hg and Pb, and the slow response time of CQD-based IR photodetectors, limit their commercial viability. This article presents a novel eSWIR photodetector that is fabricated using silver telluride (Ag2Te) CQDs. Effective thiolate ligand exchange enables a lower trap density and improved carrier mobility in CQD solids. Furthermore, a vertical p-n photodiode architecture with a favorable energy-level landscape is utilized to facilitate charge extraction, resulting in a fast, room-temperature-operable, and toxic-element-free CQD photodetector. The best eSWIR Ag2Te CQD photodetector exhibits a fall time of 72 ns, representing the fastest response time among all prior CQD-based eSWIR photodetectors, including those containing toxic elements, such as Pb and Hg.

Entropy-Driven Reversible Melting and Recrystallization of Layered Hybrid Perovskites.

Typical layered 2D A2PbX4 (A: organic ammonium cation, X: Br, I) perovskites undergo irreversible decomposition at high temperatures. Can they be designed to melt at lower temperatures without decomposition? Which thermodynamic parameter drive the melting of layered perovskites? These questions are addressed by considering the melt of A2PbX4 as a mixture of ions (like ionic liquids), and hypothesized that the increase in the structural entropy of fusion (ΔSfus) will be the driving force to decrease their melting temperature. Then to increase structural ΔSfus, A-site cations are designed that are rigid in the solid crystal, and become flexible in the molten state. Different tail groups in the A-site cations form hydrogen-, halogen- and even covalent bonding-interactions, making the cation-layer rigid in the solid form. Additionally, the rotation of ─NH3 + head group is suppressed by replacing ─H with ─CH3, further enhancing the rigidity. Six A2PbX4 crystals with high ΔSfus and low melting temperatures are prepared using this approach. For example, [I-(CH2)3-NH2(CH3)]2PbI4 reversibly melts at 388 K (decomposition temperature 500 K), and then recrystallizes back upon cooling. Consequently, melt-pressed films are grown demonstrating the solvent- and vacuum-free perovskite films for future optoelectronic devices.

Enhanced Responsivity and Photostability of Cs3Bi2I9-Based Self-Powered Photodetector via Chemical Vapor Deposition Engineering.

Lead-based halide perovskites have gained significant prominence in recent years in optoelectronics and photovoltaics, owing to their exceptional optoelectronic properties. Nonetheless, the toxicity of lead (Pb) and the stability concern pose obstacles to their potential for future large-scale market development. Herein, stable lead-free Cs3Bi2I9 (CBI) films are presented with smooth and compact morphologies synthesized via chemical vapor deposition (CVD), demonstrating their application as an UV photodetector in a self-powered way. The self-powered photodetectors (SPDs) exhibit remarkable characteristics, including a responsivity of 1.57 A W-1 and an impressive specific detectivity of 3.38 × 1013 Jones under the illumination of 365 nm at zero bias. Furthermore, the SPDs exhibit a nominal decline (≈2.2%) in the photocurrent under constant illumination over 500 h, highlighting its impressive long-term operational stability. Finally, the real-time UV-detection capability of the device is demonstrated by measuring the photocurrent under various conditions, including room light and sunlight at different times. These findings offer a new platform for synthesizing stable and high-quality perovskite films, and SPDs for advancing the development of wearable and portable electronics.

Graphene-PbS Quantum Dot Heterostructure for Broadband Photodetector with Enhanced Sensitivity.

Photodetectors converting light into electrical signals are crucial in various applications. The pursuit of high-performance photodetectors with high sensitivity and broad spectral range simultaneously has always been challenging in conventional semiconductor materials. Graphene, with its zero bandgap and high electron mobility, is an attractive candidate, but its low light absorption coefficient restricts its practical application in light detection. Integrating graphene with light-absorbing materials like PbS quantum dots (QDs) can potentially enhance its photodetection capabilities. Here, this work presents a broadband photodetector with enhanced sensitivity based on a graphene-PbS QD heterostructure. The device leverages the high carrier mobility of graphene and the strong light absorption of PbS QDs, achieving a wide detection range from ultraviolet to near-infrared. Employing a simple spinning method, the heterostructure demonstrates ultrahigh responsivity up to the order of 107 A/W and a specific detectivity on the order of 1013 Jones, showcasing significant potential for photoelectric applications.

One-Dimensional ZnO Nanorod Array Grown on Ag Nanowire Mesh/ZnO Composite Seed Layer for H2 Gas Sensing and UV Detection Applications.

Photodetectors and gas sensors are vital in modern technology, spanning from environmental monitoring to biomedical diagnostics. This paper explores the UV detection and gas sensing properties of a zinc oxide (ZnO) nanorod array (ZNA) grown on silver nanowire mesh (AgNM) using a hydrothermal method. We examined the impact of different zinc acetate precursor concentrations on their properties. Results show the AgNM forms a network with high transparency (79%) and low sheet resistance (7.23 Ω/□). A sol-gel ZnO thin film was coated on this mesh, providing a seed layer with a hexagonal wurtzite structure. Increasing the precursor concentration alters the diameter, length, and area density of ZNAs, affecting their performance. The ZNA-AgNM-based photodetector shows enhanced dark current and photocurrent with increasing precursor concentration, achieving a maximum photoresponsivity of 114 A/W at 374 nm and a detectivity of 6.37 × 1014 Jones at 0.05 M zinc acetate. For gas sensing, the resistance of ZNA-AgNM-based sensors decreases with temperature, with the best hydrogen response (2.71) at 300 °C and 0.04 M precursor concentration. These findings highlight the potential of ZNA-AgNM for high-performance UV photodetectors and hydrogen gas sensors, offering an alternative way for the development of future sensing devices with enhanced performance and functionality.

Light-Modulated Humidity Sensing in Spiropyran Functionalized MoS2 Transistors.

The optically tuneable nature of hybrid organic/inorganic heterostructures tailored by interfacing photochromic molecules with 2D semiconductors (2DSs) can be exploited to endow multi-responsiveness to the exceptional physical properties of 2DSs. In this study, a spiropyran-molybdenum disulfide (MoS2) light-switchable bi-functional field-effect transistor is realized. The spiropyran-merocyanine reversible photo-isomerization has been employed to remotely control both the electron transport and wettability of the hybrid structure. This manipulation is instrumental for tuning the sensitivity in humidity sensing. The hybrid organic/inorganic heterostructure is subjected to humidity testing, demonstrating its ability to accurately monitor relative humidity (RH) across a range of 10%-75%. The electrical output shows good sensitivity of 1.0% · (%) RH-1. The light-controlled modulation of the sensitivity in chemical sensors can significantly improve their selectivity, versatility, and overall performance in chemical sensing.

High-Performance Ultraviolet to Near-Infrared Antiambipolar Photodetectors Based on 1D CdSxSe1-x/2D Te Heterojunction.

Antiambipolar heterojunctions are regarded as a revolutionary technology in the fields of electronics and optoelectronics, enabling the switch between positive and negative transconductance within a single device, which is crucial for diverse logic circuit applications. This study pioneers a mixed-dimensional photodetector featuring antiambipolar properties, facilitated by the van der Waals integration of one-dimensional CdSxSe1-x nanowires and two-dimensional Te nanosheets. This antiambipolar device enables flexible control over carrier transport via gate voltage, thus paving new paths for future optoelectronic devices. Furthermore, by precisely managing the stoichiometry of the ternary alloy CdSxSe1-x nanowires, fine-tuning of the nanowire band structure is achieved. This allows for customizable heterojunction band alignment (Type I and Type II), enabling adjustable band alignment. Through sophisticated band engineering, optimal Type II band alignment is achieved at the CdSxSe1-x/Te interface, significantly enhancing the device's photoelectric conversion efficiency through the synergistic effect of different dimensional materials. Exhibiting outstanding photoresponse across a broad spectral range from ultraviolet to near-infrared, especially under 450 nm illumination, the CdSxSe1-x/Te heterojunction photodetector demonstrates superior performance, including an impressive responsivity of 284 A W-1, a high detectivity of 1.07 × 1017 Jones, an elevated external quantum efficiency of 7.83 × 104 %, and a swift response time of 11 µs. Ultimately, this customizable antiambipolar photodetector lays a solid foundation for the advancement of next-generation optoelectronic technologies.

Dual-Mode Semiconductor Device Enabling Optoelectronic Detection and Neuromorphic Processing with Extended Spectral Responsivity.

High-performance semiconductor devices capable of multiple functions are pivotal in meeting the challenges of miniaturization and integration in advanced technologies. Despite the inherent difficulties of incorporating dual functionality within a single device, a high-performance, dual-mode device is reported. This device integrates an ultra-thin Al2O3 passivation layer with a PbS/Si hybrid heterojunction, which can simultaneously enable optoelectronic detection and neuromorphic operation. In mode 1, the device efficiently separates photo-generated electron-hole pairs, exhibiting an ultra-wide spectral response from ultraviolet (265 nm) to near-infrared (1650 nm) wavelengths. It also reproduces high-quality images of 256 × 256 pixels, achieving a Q-value as low as 0.00437 µW cm- 2 at a light intensity of 8.58 µW cm- 2. Meanwhile, when in mode 2, the as-assembled device with typical persistent photoconductivity (PPC) behavior can act as a neuromorphic device, which can achieve 96.5% accuracy in classifying standard digits underscoring its efficacy in temporal information processing. It is believed that the present dual-function devices potentially advance the multifunctionality and miniaturization of chips for intelligence applications.

Ternary TiO2/MoS2/ZnO hetero-nanostructure based multifunctional sensing devices.

Novel sensing applications benefit from multifunctional nanomaterials responsive to various external stimuli such as mechanics, electricity, light, humidity, or pollution. While few such materials occur naturally, the careful design of synergized nanomaterials unifies the cross-coupled properties which are weak or absent in single-phase materials. In this study, 2D MoS2 integrated with ultrathin dielectric oxide layers forms hetero-nanostructures with significant impacts on carrier transport. The ternary TiO2/MoS2/ZnO hetero-nanostructures, along with their individual properties, improve the performance of multifunctional sensing devices. The synthesized hetero-nanostructure exhibits a responsivity of up to 16 mA/W to 700 nm light and responds to 5 ppm ammonia gas at room temperature. These enhancements are attributed to interface charge transfer and photogating effects. The ternary TiO2/MoS2/ZnO hetero-nanostructure is compatible with existing semiconductor fabrication technologies, making it feasible to integrate into flexible, lightweight semiconductor devices and circuits. These results may inspire new photodetectors and sensing devices based on two-dimensional (2D) layered materials for IoT applications.

Modulating Eco-friendly Colloidal AgGaS2 Quantum Dots for Highly Efficient Photodetection and Image Sensing via Direct Growth of Ternary AgInS2 Shell.

Tailoring the optoelectronic characteristics of colloidal quantum dots (QDs) by constructing a core/shell structure offers the potential to achieve high-performing solution-processed photoelectric conversion and information processing applications. In this work, the direct growth of wurtzite ternary AgInS2 (AIS) shell on eco-friendly AgGaS2 (AGS) core QDs is realized, giving rise to broadened visible light absorption, prolonged exciton lifetime and enhanced photoluminescence quantum yield (PLQY). Ultrafast transient absorption spectroscopy demonstrats that the photoinduced carrier separation and transfer kinetics of AGS QDs are significantly optimized following the AIS shell coating. As-synthesized environmentally benign AGS/AIS core/shell QDs are employed to fabricate photodetectors (PDs), showing a remarkable responsivity of 38.4 A W-1 and a detectivity of 2.4 × 1012 Jones under visible light illumination (405 nm). Moreover, the fabricated QDs-PDs exhibit superior image-sensing capability to record complex patterns with high resolution (160 × 160 pixels) under visible light illumination at 405 and 532 nm. The findings indicate that the direct growth of multinary narrow-band shell materials on eco-friendly QDs holds great promise to implement future "green", cost-effective and high-performance optoelectronic sensing/imaging systems.

The Light Wavelength, Intensity, and Biasing Voltage Dependency of the Dark and Photocurrent Densities of a Solution-Processed P3HT:PC61BM Photodetector for Sensing Applications.

The promising possibility of an organic photodetector (OPD) is emerging in the field of sensing applications for its tunable absorption range, flexibility, and large-scale fabrication abilities. In this work, we fabricated a bulk heterojunction OPD with a device structure of glass/ITO/PEDOT:PSS/P3HT:PC61BM/Al using the spin-coating process and characterized the dark and photocurrent densities at different applied bias conditions for red, green, and blue incident LEDs. The OPD photocurrent density exhibited a magnitude up to 2.5-3 orders higher compared to the dark current density at a -1 V bias while it increased by up to 3-4 orders at zero bias conditions for red, green, and blue lights, showing an increasing trend when a higher voltage is applied in the negative direction. Different OPD inner periphery shapes, the OPD to LED distance, and OPD area were also considered to bring the variation in the OPD dark and photocurrent densities, which can affect the on/off ratio of the OPD-LED hybrid system and is a critical phenomenon for any sensing application.

Recent Progress on Layered Sn and Pb-Based Mono Chalcogenides: Synthesis, Structure, Optical, and Thermoelectric Properties and Related Applications.

The research on two-dimensional materials has gained significant traction due to their potential for thermoelectric, optical, and other properties. The development of two-dimensional (2D) nanostructured-based TE generators and photodetectors has shown promising results. Over the years, researchers have played a crucial role in advancing this field, enhancing the properties of 2D materials through techniques such as doping, alloying, and various growth methods. Among these materials, black phosphorus, transition metal dichalcogenides, graphene, and IVA-VIA compounds stand out for their remarkable electronic, mechanical, and optical properties. This study presents a comprehensive review of the progress in the field, focusing on IVA-VIA compounds and their applications in TE and photodetector technologies. We summarize recent advancements in enhancing these materials' TE and optical properties and provide an overview of various synthesis techniques for their fabrication. Additionally, we highlight their potential applications as photodetectors in the infrared spectrum. This comprehensive review aims to equip researchers with a deep understanding of the TE and optical properties of 2DMs and their potential applications and to inspire further advancements in this field of research.

Ultrathin Ga2O3 Photodetector with Fast Response and Trajectory Tracking Capability Fabricated by Liquid Metal Oxidation.

Low-dimensional Ga2O3 demonstrates a unique ultraviolet photoresponse and could be used in various electronic and optical systems. However, the low-dimensional Ga2O3 photodetector is faced with the challenges of a complex preparation process and poor device performance. In this work, ultrathin Ga2O3 layers with ∼7 nm thickness are prepared on quartz rods by UV exposure to liquid gallium. Benefiting from low-density oxygen vacancy defects cured by UV exposure, the low-dimensional Ga2O3 photodetector exhibits a high response speed (rise: 64.7 µs; fall: 51.4 µs) and an exceptional linear dynamic range of 120 dB. Furthermore, the photodetector array based on these ultrathin Ga2O3 shows an effective trajectory tracking capability by monitoring UV source motion. This work develops a simple preparation method to construct a low-dimensional UV photodetector array with fast response and useful trajectory tracking capability, exhibiting the significance of ultrathin Ga2O3 in UV optoelectronics.

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.

Self-Driven Perovskite/Organic Quasi-Tandem Photodetectors Operating in Both Narrowband and Broadband Regimes.

Dual-band photodetectors (PDs) have attracted extensive research attention due to their great potential for diverse and refreshing application scenarios in full-color imaging, optical communication, and imaging detection. Here, a self-driven dual-band PD without filters and other auxiliary equipment to achieve a narrowband response in Mode 1 and a broadband response in Mode 2 was designed based on carrier-selective transmission narrowing (CSTN). The polymer material poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), which has the appropriate energy level, was selected to be the carrier-selective transmission layer. In Mode 1, the dual-band PD exhibits a near-infrared (NIR) narrowband response in 750-900 nm, which indicates a responsivity of 360 mA/W, a full-width at half-maximum (fwhm) of 81 nm, and a specific detectivity (D*) of 7.49 × 1010 Jones at 810 nm. Simultaneously, in Mode 2, the dual-band PD exhibits a UV-visible-NIR broadband responsivity of 180 mA/W and a specific detectivity (D*) of 3.8 × 1010 Jones at 520 nm. Our study provides a reliable idea for the commercial applications of dual-function photodetectors.