Boosting Photoresponse of Self-Powered InSe-Based Photoelectrochemical Photodetectors via Suppression of Interface Doping

High-Performance Flexible Broadband Photoelectrochemical Photodetector Based on Molybdenum Telluride

Flexible broadband photodetectors are desired but challenging to be fabricated for next-generation wearable intelligent optoelectronic devices. Considering the narrow bandgap and strong light absorption, molybdenum telluride (MoTe2) based photoelectrochemical photodetectors are successfully assembled by liquid phase exfoliation accompanied with the electrophoretic deposited method. This MoTe2-based photodetector shows a broadband detection in ultraviolet-near-infrared band, long-term stability within 18000 s, and fast response in millisecond-level (response time≈19 ms, recovery time≈26 ms). More importantly, even though the MoTe2 photodetector is bent and twisted at a high degree for several hundred times, it still shows excellent flexibility with stable on-off switching characteristics. Additionally, this photodetector displays a good response for rotation angles in the range from 0° to 360°, and the extracted Iph maintain almost the same value approximately 0.97 µA cm-2, suggesting an omnidirectional detection capability. This work demonstrates the proposed flexible photoanode shows a great potential in future broadband omnidirectional detection systems.

UV-Vis-NIR Broadband Self-Powered CuInS2/SnO2 Photodetectors and the Application in Encrypted Optical Communication

Photodetectors (PDs) with broadband photoresponse can meet the demand for multiband detection in complex environments, overcoming the technological complexity issue of integrated narrow-band PDs. Self-powered heterojunction PDs having ultraviolet-visible-near-infrared broadband photoresponse were constructed by using SnO2 nanopillars and CuInS2 nanoflakes. The dimension, crystalline quality, and energy level structure of the SnO2 nanopillars were regulated by changing the concentration of Sn ions in the precursor solution. The optimized interfacial energy band structure of the heterojunction can increase the transfer ability of the photogenerated carrier. The optimum performance is achieved for the CuInS2/SnO2(0.025M) PD prepared at 0.025 M Sn ion concentration in the precursor solution with the responsivities of 1.15, 6.13, and 1.02 mA/W, and detectivities of 1.19 × 1010, 6.35 × 1010, and 1.02 × 1010 Jones under 254 nm solar-blind ultraviolet light, 475 nm visible light, and 940 nm near-infrared light. Furthermore, a proof-of-concept solar-blind ultraviolet-visible-near-infrared encrypted communication system utilizing a broadband self-powered CuInS2/SnO2 PD as the receiving terminal and solar-blind ultraviolet light, ultraviolet light, visible light, and near-infrared light as the carrier and encryption protocol is proposed. The PD has great potential for applications in the field of encrypted optical communication.

Facile Semiconductor p-n Homojunction Nanowires with Strategic p-Type Doping Engineering Combined with Surface Reconstruction for Biosensing Applications

Photosensors with versatile functionalities have emerged as a cornerstone for breakthroughs in the future optoelectronic systems across a wide range of applications. In particular, emerging photoelectrochemical (PEC)-type devices have recently attracted extensive interest in liquid-based biosensing applications due to their natural electrolyte-assisted operating characteristics. Herein, a PEC-type photosensor was carefully designed and constructed by employing gallium nitride (GaN) p-n homojunction semiconductor nanowires on silicon, with the p-GaN segment strategically doped and then decorated with cobalt-nickel oxide (CoNiOx). Essentially, the p-n homojunction configuration with facile p-doping engineering improves carrier separation efficiency and facilitates carrier transfer to the nanowire surface, while CoNiOx decoration further boosts PEC reaction activity and carrier dynamics at the nanowire/electrolyte interface. Consequently, the constructed photosensor achieves a high responsivity of 247.8 mA W-1 while simultaneously exhibiting excellent operating stability. Strikingly, based on the remarkable stability and high responsivity of the device, a glucose sensing system was established with a demonstration of glucose level determination in real human serum. This work offers a feasible and universal approach in the pursuit of high-performance bio-related sensing applications via a rational design of PEC devices in the form of nanostructured architecture with strategic doping engineering.

Progress in Advanced Infrared Optoelectronic Sensors

Infrared optoelectronic sensors have attracted considerable research interest over the past few decades due to their wide-ranging applications in military, healthcare, environmental monitoring, industrial inspection, and human-computer interaction systems. A comprehensive understanding of infrared optoelectronic sensors is of great importance for achieving their future optimization. This paper comprehensively reviews the recent advancements in infrared optoelectronic sensors. Firstly, their working mechanisms are elucidated. Then, the key metrics for evaluating an infrared optoelectronic sensor are introduced. Subsequently, an overview of promising materials and nanostructures for high-performance infrared optoelectronic sensors, along with the performances of state-of-the-art devices, is presented. Finally, the challenges facing infrared optoelectronic sensors are posed, and some perspectives for the optimization of infrared optoelectronic sensors are discussed, thereby paving the way for the development of future infrared optoelectronic sensors.

High-Sensitivity Photoelectrochemical Ultraviolet Photodetector with Stable pH-Universal Adaptability Based on Whole Single-Crystal Integrated Self-Supporting 4H-SiC Nanoarrays

Emerging photoelectrochemical (PEC) photodetectors (PDs) have notable advantages over conventional PDs and have attracted extensive attention. However, harsh liquid environments, such as those with high corrosivity and attenuation, substantially restrict their widespread application. Moreover, most PEC PDs are constructed by assembling numerous nanostructures on current collector substrates, which inevitably contain abundant interfaces and defects, thus greatly weakening the properties of PDs. To address these challenges, a high-performance pH-universal PEC ultraviolet (UV) PD based on a whole single-crystal integrated self-supporting 4H-SiC nanopore array photoelectrode is constructed, which is fabricated using a two-step anodic oxidation approach. The PD exhibits excellent photodetection behavior, with high responsivity (218.77 mA W-1 ), detectivity (6.64 × 1013  Jones), external quantum efficiency (72.47%), and rapid rise/decay times (17/48 ms) under 375 nm light illumination with a low intensity of 0.15 mW cm-2 and a bias voltage of 0.6 V, which is fall in the state-of-the-art of the wide-bandgap semiconductor-based PDs reported thus far. Furthermore, the SiC PEC PD exhibits excellent photoresponse and long-term operational stability in pH-universal liquid environments. The improved photodetection performance of the SiC PEC PD is primarily attributed to the synergistic effect of the nanopore array structure, integrated self-supporting configuration, and single-crystal structure of the whole photoelectrode.

Mist Chemical Vapor Deposition of Bi13S18I2 for Photoelectrochemical-type Photodetection

Bismuth-based ternary compounds have attracted much attention owing to their various merits, such as low toxicity and tunable electrical and optical properties. However, these compounds are yet to be understood due to the lack of suitable targets limited by immature synthesis techniques. In this work, we aimed at the synthesis, properties investigation, and photodetection application of Bi13S18I2. Mist chemical vapor deposition was adopted for the deposition of the Bi13S18I2 thin film for the first time. The deposition mechanism was discussed from the perspective of crystal phase and surface morphology. Based on the Bi13S18I2 thin film synthesized at optimal temperature, we constructed a photoelectrochemical-type photodetector. The photodetection performance was evaluated from the points of electrolyte composition, working temperature, and bias voltage. This study would pave the way for the controllable synthesis and applications of bismuth-based ternary compounds.

Optoelectronic Synapses Based on MXene/Violet Phosphorus van der Waals Heterojunctions for Visual-Olfactory Crossmodal Perception

The crossmodal interaction of different senses, which is an important basis for learning and memory in the human brain, is highly desired to be mimicked at the device level for developing neuromorphic crossmodal perception, but related researches are scarce. Here, we demonstrate an optoelectronic synapse for vision-olfactory crossmodal perception based on MXene/violet phosphorus (VP) van der Waals heterojunctions. Benefiting from the efficient separation and transport of photogenerated carriers facilitated by conductive MXene, the photoelectric responsivity of VP is dramatically enhanced by 7 orders of magnitude, reaching up to 7.7 A W-1. Excited by ultraviolet light, multiple synaptic functions, including excitatory postsynaptic currents, paired-pulse facilitation, short/long-term plasticity and "learning-experience" behavior, were demonstrated with a low power consumption. Furthermore, the proposed optoelectronic synapse exhibits distinct synaptic behaviors in different gas environments, enabling it to simulate the interaction of visual and olfactory information for crossmodal perception. This work demonstrates the great potential of VP in optoelectronics and provides a promising platform for applications such as virtual reality and neurorobotics.

Direct growth Bi2O2Se nanosheets on SiO2/Si substrate for high-performance and broadband photodetector

Bi2O2Se, a newly emerging two-dimensional (2D) material, has attracted significant attention as a promising candidate for optoelectronics applications due to its exceptional air stability and high mobility. Generally, mica and SrTiO3substrates with lattice matching are commonly used for the growth of high-quality 2D Bi2O2Se. Although 2D Bi2O2Se grown on these insulating substrates can be transferred onto Si substrate to ensure compatibility with silicon-based semiconductor processes, this inevitably introduces defects and surface states that significantly compromise the performance of optoelectronic devices. Herein we employ Bi2Se3as the evaporation source and oxygen reaction to directly grow Bi2O2Se nanosheets on Si substrate through a conventional chemical vapor deposition method. The photodetector based on the Bi2O2Se nanosheets on Si substrate demonstrates outstanding optoelectronics performance with a responsivity of 379 A W-1, detectivity of 2.9 × 1010Jones, and rapid response time of 0.28 ms, respectively, with 532 nm illumination. Moreover, it also exhibits a broadband photodetection capability across the visible to near-infrared range (532-1300 nm). These results suggest that the promising potential of Bi2O2Se nanosheets for high-performance and broadband photodetector applications.

A self-powered photoelectrochemical biosensing platform for H-FABP monitoring mediated by CsPbBr3@COF-V

Advanced bioelectronic detection based on the integration of modern optical electronics and biological systems has a broad prospect. The strategy of cathode signal amplification in self-powered photoelectrochemical (PEC) immunosensors with excellent performance is rarely reported in the field of immune analysis. Herein, the work demonstrates a self-powered PEC biosensor formed with BiOI photocathode and WO3/SnS2/ZnS photoanode, and CsPbBr3@COF-V was used as the photocathode signal quenching source for the quantitative monitoring of heart fatty acid binding protein (H-FABP). The high efficiency and stable self-powered biosensor formed not only provides continuous and powerful photocurrent response for bioanalysis through reasonable stepped band structure, but also effectively eliminates the interference of reducing substances. The quenching source CsPbBr3@COF-V greatly affects the photocurrent response due to steric hindrance, weak conductivity, competition with the substrate for dissolved oxygen and excitation light source. And the intervention of this key factor achieves multiple signal amplification effect and opens up an innovative vision for self-powered PEC immunosensor. Taking H-FABP as a representative analyte, the proposed signal amplification self-powered photoelectrochemical presents a broad linear range from 0.0005 to 150 ng/mL with the detection limit of 0.19 pg/mL.

Polarization enhanced photoresponse of InSe via 2D ferroelectric CuCrP2S6

Two-dimensional CuCrP2S6 possesses significant potential for low-power non-volatile devices owing to its multiferroic properties. Nonetheless, comprehensive investigations regarding the modulation of CuCrP2S6 polarization for enhancing semiconductor photodetection capabilities and its potential applications in ferroelectric non-volatile devices are still relatively scarce. In this study, we present a novel, non-volatile, tunable photodetector engineered through the integration of a ferroelectric heterostructure comprising CuCrP2S6 and InSe. Our findings reveal that distinct ferroelectric polarization states of CuCrP2S6 exert varying modulation effects on the InSe photodetection performance. Notably, optimized results give a responsivity of 1839 A W-1 and a detectivity of 1.9 × 1012 Jones at a 300 nm wavelength, featuring a substantial 20.7-fold difference in responsivity between the two polarization states. This investigation underscores the immense potential of CuCrP2S6 in the development of non-volatile, multi-state optoelectronic devices.

High-Sensitivity Self-Powered Photodetector Fibers Using Hierarchical Heterojunction Photoelectrodes Enable Wearable Amphibious Optoelectronic Textiles

Fiber-shaped photodetectors (FPDs) with multidirectional light absorption properties offer exciting opportunities for intelligent optoelectronic textiles. However, achieving FPDs capable of working in ampule environments, especially with high sensitivity, remains a fundamental challenge. Here, quasi-solid-state twisted-fiber photoelectrochemical photodetectors (FPPDs) consisting of photoanode, gel electrolyte, and counter electrode are successfully assembled. In situ decorated n-type one-dimensional (1D) TiO2 nanowire arrays with 2D Ni-Fe metal-organic framework (NiFeMOF) nanosheets serve as hierarchical heterojunction photoanodes, thereby optimizing carrier transfer dynamics at the photoanode/electrolyte interface. As expected, the resulting self-powered FPPD exhibits 88.6 mA W-1 high responsiveness and a < 30 ms fast response time. Significantly, our FPPD can operate in both terrestrial and aquatic environments thanks to its intrinsic ionic properties, making it a versatile tool for detecting ultraviolet light on land and facilitating optical communication underwater. These high-sensitivity self-powered FPPDs with hierarchical heterojunction photoelectrodes hold promise for the development of wearable amphibious optoelectronic textiles.

Integrating High-Sensitivity Photodetector and High-Energy Aqueous Battery in All-in-One Triple-Twisted Fiber

Fiber-shaped photodetectors (FPDs) have attracted special attention to wearable health monitoring due to their 3D absorption capabilities. However, the practical application of traditional FPDs is severely limited by the irreversible degradation of performance caused by vulnerable interface compatibility on complex deformation and a single function. Here, an integrated photoelectrochemical FPD/battery device (FPDB) is designed, consisting of a common electrode, photoanode, anode, and sol-gel electrolyte as an isolation layer, which not only effectively avoids the short circuit problem of FPD but also endows high-efficiency energy storage capacity. As expected, the resulting all-in-one triple-twisted fiber-shaped FPDB simultaneously achieves high responsiveness of 151.45 mA W-1 and excellent volume capacity of 18.75 mAh cm-3. Such a stable architectural design and multifunctional integration of functional fibers accelerate the development of next-generation wearable fabrics.

An A2 B2 O7 -Type High-Entropy Oxide for Efficient Photoelectrochemical Photodetector with Excellent Long-Term Stability

Optoelectronics with excellent long-term stability is meaningful for practical applications. Herein, for the first time, an A2 B2 O7 type high-entropy oxide of (La0.2 Ce0.2 Nd0.2 Gd0.2 Bi0.2 )2 Ti2 O7 (ATO) is synthesized and applied for photoelectrochemical photodetection. The lattice distortion, highly dispersed metal composition, and exposed active sites of ATO are beneficial for the fast separation and transmission of photogenerated electron/hole pairs, endowing ATO-based devices with good photodetection performance. Both the density functional theory calculations and the nondegenerate transient absorption spectroscopy demonstrate the good optoelectronic properties of ATO. The systematic experimental studies reveal the tunable photodetection capability of ATO-based photodetector (PD) in the visible region. A photocurrent of 772.00 nA cm-2 and a responsivity of 4.02 µA W-1 can be achieved as the PD in 1.0 m KOH with the bias potential of 0.6 V. Importantly, the robust and reproducible ON/OFF signals of the PD can be verified and there is only ≈5.00% attenuation in photocurrent even after 6 months, revealing the great potential of high- entropy oxides for practical applications.

Hydrogen-Terminated Two-Dimensional Germanane/Silicane Alloys as Self-Powered Photodetectors and Sensors

2D monoelemental materials, particularly germanene and silicene (the single layer of germanium and silicon), which are the base materials for modern electronic devices demonstrated tremendous attraction for their 2D layer structure along with the tuneable electronics and optical band gap. The major shortcoming of synthesized thermodynamically very unstable layered germanene and silicene with their inclination toward oxidation was overcome by topochemical deintercalation of a Zintl phase (CaGe₂, CaGe_1.5Si_0.5, and CaGeSi) in a protic environment. The exfoliated Ge-H, Ge_0.75Si_0.25H, and Ge_0.5Si_0.5H were successfully synthesized and employed as the active layer for photoelectrochemical photodetectors, which showed broad response (420-940 nm), unprecedented responsivity, and detectivity on the order of 168 μA W^-1 and 3.45 × 10⁸ cm Hz^1/2 W^-1, respectively. The sensing capability of exfoliated germanane and silicane composites was explored using electrochemical impedance spectroscopy with ultrafast response and recovery time of less than 1 s. These positive findings serve as the application of exfoliated germanene and silicene composites and can pave a new path to practical applications in efficient future devices.

Ultrathin CuBi2O4 on a bipolar Bi2O3 nano-scaffold: a self-powered broadband photoelectrochemical photodetector with improved responsivity and response speed

CuBi₂O₄ is a promising photoactive material for photoelectrochemical (PEC) broadband photodetectors due to its suitable band structure, but its photo-responsivity is severely limited by the short carrier diffusion length and long light penetration depth. To address the trade-off between light absorption and charge separation, a nano-structured bipolar Bi₂O₃ host scaffold was coupled with an ultrathin CuBi₂O₄ light absorbing layer to construct a host-guest Bi₂O₃/CuBi₂O₄ photocathode. The work function of the bipolar Bi₂O₃ scaffold lies in between FTO and CuBi₂O₄, making Bi₂O₃ a suitable back contact layer for hole transport. Compared with the flat CuBi₂O₄ and Bi₂O₃ scaffold counterpart, the nanostructured Bi₂O₃/CuBi₂O₄ exhibits significantly improved light absorption and enhanced charge separation efficiency. The Bi₂O₃/CuBi₂O₄ PEC photodetector can be self-powered and demonstrates a broad photo-response ranging from ultraviolet (UV) to near infrared (NIR). It shows a high responsivity of 75 mA W^-1 and a remarkable short response time of 0.18 ms/0.19 ms. Bi₂O₃/CuBi₂O₄ prepared by magnetron sputtering demonstrates great potential for rapid PEC photodetection in a wide optical domain.

Achieving Record-High Photoelectrochemical Photoresponse Characteristics by Employing Co3O4 Nanoclusters as Hole Charging Layer for Underwater Optical Communication

The physicochemical properties of a semiconductor surface, especially in low-dimensional nanostructures, determine the electrical and optical behavior of the devices. Thereby, the precise control of surface properties is a prerequisite for not only preserving the intrinsic material quality but also manipulating carrier transport behavior for promoting device characteristics. Here, we report a facile approach to suppress the photocorrosion effect while boosting the photoresponse performance of n-GaN nanowires in a constructed photoelectrochemical-type photodetector by employing Co₃O₄ nanoclusters as a hole charging layer. Essentially, the Co₃O₄ nanoclusters not only alleviate nanowires from corrosion by optimizing the oxygen evolution reaction kinetics at the nanowire/electrolyte interface but also facilitate an efficient photogenerated carrier separation, migration, and collection process, leading to a significant ease of photocurrent attenuation (improved by nearly 867% after Co₃O₄ decoration). Strikingly, a record-high responsivity of 217.2 mA W^-1 with an ultrafast response/recovery time of 0.03/0.02 ms can also be achieved, demonstrating one of the best performances among the reported photoelectrochemical-type photodetectors, that ultimately allowed us to build an underwater optical communication system based on the proposed nanowire array for practical applications. This work provides a perspective for the rational design of stable nanostructures for various applications in photo- and biosensing or energy-harvesting nanosystems.

2D Few-Layered PdPS: Toward High-Efficient Self-Powered Broadband Photodetector and Sensors

Photodetectors and sensors have a prominent role in our lives and cover a wide range of applications, including intelligent systems and the detection of harmful and toxic elements. Although there have been several studies in this direction, their practical applications have been hindered by slow response and low responsiveness. To overcome these problems, we have presented here a self-powered (photoelectrochemical, PEC), ultrasensitive, and ultrafast photodetector platform. For this purpose, a novel few-layered palladium-phosphorus-sulfur (PdPS) was fabricated by shear exfoliation for effective photodetection as a practical assessment. The characterization of this self-powered broadband photodetector demonstrated superior responsivity and specific detectivity in the order of 33 mA W^-1 and 9.87 × 10¹⁰ cm Hz^1/2 W^-1, respectively. The PEC photodetector also exhibits a broadband photodetection capability ranging from UV to IR spectrum, with the ultrafast response (∼40 ms) and recovery time (∼50 ms). In addition, the novel few-layered PdPS showed superior sensing ability to organic vapors with ultrafast response and a recovery time of less than 1 s. Finally, the photocatalytic activity in the form of hydrogen evolution reaction was explored due to the suitable band alignment and pronounced light absorption capability. The self-powered sensing platforms and superior catalytic activity will pave the way for practical applications in efficient future devices.

Ultrathin In2 O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In₂ O₃ ) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In₂ O₃ NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36 mA W^-1 and a high specific detectivity of 4.43 × 10¹¹ Jones under 254 nm irradiation, which originates from the smaller charge transfer resistance (R_ct ) at the In₂ O₃ NSs/electrolyte interface. The light absorption of In₂ O₃ NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In₂ O₃ NSs PEC PDs is 1567, which is 30 times higher than that of In₂ O₃ nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In₂ O₃ NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In₂ O₃ NSs have potential in underwater optoelectronic devices.

Designing Inorganic Semiconductors with Cold-Rolling Processability

While metals can be readily processed and reshaped by cold rolling, most bulk inorganic semiconductors are brittle materials that tend to fracture when plastically deformed. Manufacturing thin sheets and foils of inorganic semiconductors is therefore a bottleneck problem, severely restricting their use in flexible electronic applications. It is recently reported that a few single-crystalline 2D van der Waals (vdW) semiconductors, such as InSe, are deformable under compressive stress. Here it is demonstrated that intralayer fracture toughness can be tailored via compositional design to make inorganic semiconductors processable by cold rolling. Systematic ab initio calculations covering a range of van der Waals semiconductors homologous to InSe are reported, leading to material-property maps that forecast trends in both the susceptibility to interlayer slip and the intralayer fracture toughness against cracking. GaSe is predicted, and experimentally confirmed, to be practically amenable to being rolled to large (three quarters) thickness reduction and length extension by a factor of three. The fracture toughness and cleavage energy are predicted to be 0.25 MPa m^0.5 and 15 meV Å^-2 , respectively. The findings open a new realm of possibility for alloy selection and design toward processing-friendly group-III chalcogenides for practical applications.