Excellent Photoresponse Performance Research Articles

Two-Dimensional GeS/SnSe2 Tunneling Photodiode with Bidirectional Photoresponse and High Polarization Sensitivity.

A two-dimensional (2D) broken-gap (type-III) p-n heterojunction has a unique charge transport mechanism because of nonoverlapping energy bands. In light of this, type-III band alignment can be used in tunneling field-effect transistors (TFETs) and Esaki diodes with tunable operation and low consumption by highlighting the advantages of tunneling mechanisms. In recent years, 2D tunneling photodiodes have gradually attracted attention for novel optoelectronic performance with a combination of strong light-matter interaction and tunable band alignment. However, an in-depth understanding of the tunneling mechanisms should be further investigated, especially for developing electronic and optoelectronic applications. Here, we report a type-III tunneling photodiode based on a 2D multilayered p-GeS/n+-SnSe2 heterostructure, which is first fabricated by the mechanical exfoliation and dry transfer method. Through the Simmons approximation, its various tunneling transport mechanisms dependent on bias and light are demonstrated as the origin of excellent bidirectional photoresponse performance. Moreover, compared to the traditional p-n photodiode, the device enables bidirectional photoresponse capability, including maximum responsivity values of 43 and 8.7 A/W at Vds = 1 and -1 V, respectively, with distinctive photoactive regions from the scanning photocurrent mapping. Noticeably, benefiting from the in-plane anisotropic structure of GeS, the device exhibits an enhanced photocurrent anisotropic ratio of 9, driven by the broader depletion region at Vds = -3 V under 635 nm irradiation. Above all, the results suggest that our designed architecture can be potentially applied to CMOS imaging sensors and polarization-sensitive photodetectors.

High‐Performance Broadband Flexible Photodetectors Based on Ti3C2Tx MXene/Pyramidal Thin Si Heterostructures with Light Trapping Effect for Heart Rate Detection

AbstractHigh‐performance flexible photodetectors are urgently demanded for application in many emerging domains including flexible, wearable, portable, and stretchable optoelectronics. In this work, a highly efficient flexible photodetector made of a Ti3C2Tx MXene/pyramidal thin Si heterostructure is successfully fabricated. Thanks to the remarkable light trapping effect as confirmed by numerical modeling based on finite‐element method, the as‐constructed detector demonstrates excellent photoresponse performance in a broadband wavelength spectrum. The optimal responsivity, specific detectivity, and response speed reach ≈530 mA W−1, ≈1.21 × 1012 Jones and 30/14 µs, respectively, at zero bias under near‐infrared light illumination. Specifically, the responsivity is greatly enhanced by ≈2.65 times, as compared with a planar counterpart. In addition, the light detector can maintain its outstanding photoresponse properties upon 1000 cycles of bending test or at diverse bending radii of curvature, owing to its prominent mechanical flexibility and robust bending endurance. Finally, the capability of monitoring the heart rate of a person in a wideband wavelength spectrum and at various bending radii of curvature is presented. The above results imply the huge potential of the flexible light detector for use in some applications such as wearable health monitoring.

Significant Suppression of Dark Current in a Surface Acoustic Wave Assisted MoS2 Photodetector

Abstract2D materials are considered as potential candidates for the next generation of optoelectronic materials. However, their optical absorption is typically weak due to thickness limitations, greatly restricting the photodetection capabilities of devices. To enhance the photoelectric gain of 2D materials or devices and improve detection sensitivity, various modulation methods such as strain, electric field, and magnetic field are commonly introduced. Among them, surface acoustic wave (SAW) represents a unique and effective modulation approach. In this study, photodetectors are fabricated based on few‐layer MoS2 on a SAW delay line on a LiTaO3 substrate. The interaction between SAW and MoS2 successfully manipulates the optoelectronic performance of the MoS2‐based devices. Under the influence of SAW, the dark current of the devices is significantly reduced by more than two orders of magnitude, while the photocurrent remains almost unchanged, resulting in excellent photoresponse performance. The devices provide a promising pathway for high‐performance optoelectronic applications and reveal a new possibility for acoustic devices in optoelectronics.

Bandgap Engineering of BiIns Nanowire for Wide‐Spectrum, High‐Responsivity, and Polarimetric‐Sensitive Detection

AbstractOptical devices based on alloying semiconductors offer a plethora of new possibilities for detection across a broad spectrum. Among these devices, nanowire‐based devices have gained much attention due to their remarkable specific surface area properties in terms of material synthesis, device structure, and performance. In this work, (BixIn1−x)2S3 nanowires are designed by controlling the ratio of Bi and In atoms. The atomic ratio directly affects the electronic band structure of the crystal, thereby further optimizing the performance of optoelectronic devices. According to the experimental results, Bi1.28In0.72S3 nanowire‐based photodetectors obtain the most excellent photoresponse performance. The typical device demonstrates a spectral response from deep ultraviolet (DUV 254 nm) to near‐infrared (NIR 1064 nm) and achieves a maximum dichroic ratio of photoresponse of 1.5 under polarization‐angle‐sensitive detection in the 266–808 nm range. It also exhibits a photoresponse of 10.1 A W−1 and a photodetectivity of 5.7 × 1010 Jones under 532 nm light irradiation. Additionally, the photodetector displays a fast response speed with a rise/fall time of 5/4.7 ms. Finally, “CSU” and puppy images produced by this device further demonstrate the effectiveness of alloying semiconductors in creating wide‐spectrum, high‐responsivity, fast‐response, and polarimetric‐sensitive photodetectors.

Lead Monoxide Nanostructures for Nanophotonics: A Review

Black-phosphorus-analog lead monoxide (PbO), as a new emerging 2D material, has rapidly gained popularity in recent years due to its unique optical and electronic properties. Recently, both theoretical prediction and experimental confirmation have revealed that PbO exhibits excellent semiconductor properties, including a tunable bandgap, high carrier mobility, and excellent photoresponse performance, which is undoubtedly of great interest to explore its practical application in a variety of fields, especially in nanophotonics. In this minireview, we firstly summarize the synthesis of PbO nanostructures with different dimensionalities, then highlight the recent progress in the optoelectronics/photonics applications based on PbO nanostructures, and present some personal insights on the current challenges and future opportunities in this research area. It is anticipated that this minireview can pave the way to fundamental research on functional black-phosphorus-analog PbO-nanostructure-based devices to meet the growing demands for next-generation systems.

Simulation Photosynthesis Improves the Photoresponse Performance of Cr2Ge2Te6 Nanosheets for High-Performance Self-Powered Photoelectrochemical Photodetectors

Two-dimensional (2D) semiconductor materials have been extensively studied as excellent candidates for future optoelectronic devices. Cr2Ge2Te6, as a two-dimensional semiconductor material, has attracted extensive interest in the field of photodetectors due to its excellent light absorption properties and suitable band gap. Inspired by biological photosynthesis, this study constructed a high-performance biomimetic self-powered photoelectrochemical-type flexible photodetector using liquid-stripped Cr2Ge2Te6 nanosheets as the photoanode. The device exhibits obvious self-powered photoresponse behavior and excellent photoresponse performance with a responsivity of 54.4 μA/W. Furthermore, the addition of nicotinamide adenine dinucleotide phosphate (NADPH) effectively consumes the photo-excited holes on the Cr2Ge2Te6 nanosheets to inhibit the recombination of photogenerated electron–hole pairs, and the cyclic regeneration of NADPH is realized by adding adenosine triphosphate. In addition, the flexible photodetector also exhibits excellent stability and durability, and it still maintains good photoresponse characteristics after 1000 times of bending and folding. Our work fully confirms that it is an effective means to improve the photoresponse performance of 2D materials by simulating biological photosynthesis, and it also provides theoretical and experimental guidance for the research and development of high-performance biomimetic devices.

Stereopsis-Inspired 3D Visual Imaging System Based on 2D Ruddlesden-Popper Perovskite.

Stereopsis is of great important functions for humans to perceive and interact with the world. To realize the function of stereoscopic imaging, optoelectronic sensors shall possess good photoresponsive performance, multidirectional sensing, and 3D building capabilities. However, the current imaging sensors are mainly focused on 2D imaging, limiting their practical application scenarios. In this study, a stereopsis-inspired flexible 3D visual imaging system (VIS) based on 2D Ruddlesden-Popper perovskite is demonstrated. The 3D-VIS consists of 800 device units, each of which demonstrates excellent photoresponse performance, mechanical characteristics, and environmental stability. In addition to the capability of detecting 2D reflective images, the 3D-VIS realizes the function of detecting the depth of field and fusing object projections of two directions to invert the 3D image by utilizing voxels to rebuild the spatial structure of the object. In the future, the 3D-VIS will have broad application prospects in medical imaging, virtual reality, industrial automation, and other fields.

Fully Transparent Ultraviolet Photodetector with Ultrahigh Responsivity Enhanced by MXene‐Induced Photogating Effect

AbstractTransparent photodetectors with the optical signal recognition and conversion capabilities are the core component for smart sensors and next‐generation “see‐through” optoelectronics. However, it is usually difficult to have both excellent optical transmittance and photoresponse performance, which hinders the practicality of transparent photodetectors. Herein, a photogating effect enhanced transparent ultraviolet (UV) photodetector is demonstrated based on the TiO2/MXene van der Waals heterojunction. By simply spin‐coating MXene nanosheets on TiO2 film, the UV photodetector exhibits significantly enhanced performance, such as ultrahigh responsivity (202.4 A/W), large specific detectivity (1.79 × 1014 Jones) and outstanding external quantum efficiency (1.02 × 105%), which are three orders of magnitude higher than those of pure TiO2 film. Meanwhile, the device exhibits up to 95% transparency in the visible range. Both the experimental results and theory calculations indicate that local Schottky junctions are established at the TiO2/MXene interface. These local junctions exert a giant photogating effect under illumination, which can facilitate the separation of photogenerated carriers and improve the photodetection performance. Moreover, the transparent photodetector has been successfully applied in a UV index wireless sensing system. This work demonstrates the ingenious application of MXene in optoelectronics and provides insight into the design of high‐performance transparent photodetectors.

High-performance Al-doped ZnO flexible ultraviolet photodetector via piezo-phototronic effect

Al-doped ZnO (AZO) flexible ultraviolet (UV) photodetectors were fabricated on polyethylene terephthalate substrates by radio frequency magnetron sputtering technique at room temperature. The single-layer AZO photodetector has a high photocurrent/dark current ratio and exhibits excellent photoresponse performance under UV illumination. When the tensile strain increases from 0 to 0.33, the photocurrent gradually increases, and the sensitivity and linear dynamic range increase by 10 times and 1.5 times, respectively. Under 23.5 mW/cm2 UV illumination at 4 V bias, the rise time and fall time are 0.2 and 0.3 s, respectively, showing that the AZO flexible UV photodetector has good reproducibility and stability. The energy band diagrams before and after applying tensile strain are analyzed to further study the interface modulation behavior. The results reveal that the piezo-phototronic effect has an important influence on the performance optimization and modulation of flexible UV photodetectors.

Self‐Powered Photodetector Based on Perovskite/NiOx Heterostructure for Sensitive Visible Light and X‐Ray Detection

AbstractSelf‐powered halide perovskite X‐ray detectors have evoked busting interests because they present outstanding properties such as low power consumption, high sensitivity, and integrability without external power source. Nevertheless, existing self‐powered X‐ray detectors exhibit low sensitivity due to the insufficient charge separation and transport. Herein, a self‐powered photodetector for sensitive X‐ray and photodetection based on single‐crystalline perovskite FAPbBr3/NiOx heterostructure is demonstrated. The built‐in field of FAPbBr3/NiOx heterojunction provides a driving force for separation and transport of photoexcited carriers. Without an external power supply, the photodetector presents excellent photoresponse performance under 450 nm light illumination, including high photoresponsivity (123.6 mA W−1), good detectivity (D = 7.1 × 1011 Jones), and ultrafast response/recovery time (10/200 ns). Simultaneously, the device achieves photovoltaic effect of 0.80 V and a large mobility–lifetime product of 1.1 × 10−3 cm2 V−1, which enable a superior X‐ray sensitivity of 402 µC Gyair−1 cm−2 at zero bias voltage. These results imply that the simple combination of perovskite single crystal and a hole transporting layer provides a flexible platform for the realization of energy‐saving self‐powered photodetector in visible light and X‐rays.

Growth, Raman Scattering Investigation and Photodetector Properties of 2D SnP.

As an important metal phosphides material, 2D tin phosphides (SnPx 0< x≤3) have been theoretically predicted to have intriguing physicochemical properties and potential applications in electronics, optoelectronics, and energy fields. However, the synthesis of high-quality 2D SnP single crystal has not been reported due to the lack of efficiency and reliable growth method. Here, a facile atmospheric pressure chemical vapor deposition (APCVD) method is developed to realize the growth of high-quality 2D SnP nanosheets, by employing tin (Sn) foil as both liquid metal substrates and reaction precursor. Temperature-dependent and angle-resolved polarization Raman spectra observed Raman peaks located at 142.6, 303.3, and 444.2 cm-1 are concluded to belong to A1g mode, which are consistent with the theoretical calculation results. Moreover, the field-effect transistor (FET) devices based on SnP nanosheets show a typical n-type characteristic with an on/off ratio of 103 at 200 K. SnP nanosheets also demonstrate excellent photoresponse performance under the illumination of 473, 532, and 639nm lasers, which can be tuned by Vgs , Vds , and light power density. It is believed that these findings can provide the first-hand experimental information for the future study of 2D SnP nanosheets.

Self‐Driven High Performance Broadband Photodetector Based on SnSe/InSe van der Waals Heterojunction

AbstractSnSe as a van der Waals (vdW) layered material has an extremely low light‐dark current ratio and renders its application in high‐performance optoelectronics. Herein, a SnSe/InSe vertical‐vdW heterojunction with built‐in electrical field favorable for suppressing the dark current is achieved. The SnSe/InSe heterojunction behaves as a self‐driven photodetector with a typical rectification behavior, photovoltaic effect, and broadband detection ranging from visible to near infrared light (405–808 nm). Moreover, the SnSe/InSe photodetector at near infrared 808 nm still exhibits excellent and balanced photoresponse performance with R of 350 mA W−1, external quantum efficiency of 48% and detectivity of 5.8 × 1010 Jones, respectively. The results pave the way for the applications of the novel SnSe/InSe vdW heterostructures in broadband photodetectors and photovoltaic devices.

Self-powered CsCu2I3/Si heterojunction UV photodetectors prepared by pulsed-laser deposition

All-inorganic perovskite CsCu2I3 thin films have been prepared on Si(100) substrates by pulsed laser deposition technology. And the influence of the substrate temperatures on the morphology, structure and optical properties of the CsCu2I3 films was investigated by SEM, XRD, PL and absorption spectra. A prototype CsCu2I3/Si n-n heterojunction UV photodetection device was constructed with LiF/Al and Au Ohmic contact electrodes. The photodetector demonstrates excellent self-powered photoresponse performance with an on/off ratio of ~2150 at 0 V. The device also exhibits good spectral selectivity and photoresponse characteristics in the UV range (280–370 nm). The peak responsivity (R) and specific detectivity (D*) of the CsCu2I3/Si heterojunction device are 7.1 mA/W and 2.6 × 1011 Jones at 0 V and 330 nm (~700 μW/cm2) light illumination, and shows good stability and reproducibility.

Polymorphic Ga2S3 nanowires: phase-controlled growth and crystal structure calculations.

The polymorphism of nanostructures is of paramount importance for many promising applications in high-performance nanodevices. We report the chemical vapor deposition synthesis of Ga2S3 nanowires (NWs) that show the consecutive phase transitions of monoclinic (M) → hexagonal (H) → wurtzite (W) → zinc blende (C) when lowering the growth temperature from 850 to 600 °C. At the highest temperature, single-crystalline NWs were grown in the thermodynamically stable M phase. Two types of H phase exhibited 1.8 nm periodic superlattice structures owing to the distinctively ordered Ga sites. They consisted of three rotational variants of the M phase along the growth direction ([001]M = [0001]H/W) but with different sequences in the variants. The phases shared the same crystallographic axis within the NWs, producing novel core–shell structures to illustrate the phase evolution. The relative stabilities of these phases were predicted using density functional theory calculations, and the results support the successive phase evolution. Photodetector devices based on the p-type M and H phase Ga2S3 NWs showed excellent UV photoresponse performance.

A Facile Approach for Elemental‐Doped Carbon Quantum Dots and Their Application for Efficient Photodetectors (Small 52/2021)

Photodetectors The cover image describes the design of three-electrode photo-electrochemical photodetectors based on lanthanide-doped carbon quantum dots (CQDs). Owing to the coordination of lanthanides and internal energy transfer between lanthanides and CQDs, the as-fabricated photodetectors not only show an excellent photo-response performance, but also exhibit a narrow-band response behavior. More information can be found in article number 2105683 by Lingfeng Gao, Hans Ågren, Han Zhang, and co-workers.

Ultra‐Small 2D PbS Nanoplatelets: Liquid‐Phase Exfoliation and Emerging Applications for Photo‐Electrochemical Photodetectors

2D PbS nanoplatelets (NPLs) form an emerging class of photoactive materials and have been proposed as robust materials for high-performance optoelectronic devices. However, the main drawback of PbS NPLs is the large lateral size, which inhibits their further investigations and practical applications. In this work, ultra-small 2D PbS NPLs with uniform lateral size (11.2± 1.7nm) and thickness (3.7± 0.9nm, ≈6 layers) have been successfully fabricated by a facile liquid-phase exfoliation approach. Their transient optical response and photo-response behavior are evaluated by femtosecond-resolved transient absorption and photo-electrochemical (PEC) measurements. It is shown that the NPLs-based photodetectors (PDs) exhibit excellent photo-response performance from UV to the visible range, showing extremely high photo-responsivity (27.81mA W-1 ) and remarkable detectivity (3.96 × 1010 Jones), which are figures of merit outperforming currently reported PEC-type PDs. The outstanding properties are further analyzed based on the results of first-principle calculations, including electronic band structure and free energies for the oxygen evolution reaction process. This work highlights promising applications of ultra-small 2D PbS NPLs with the potential for breakthrough developments also in other fields of optoelectronic devices.

2D Perovskite Single Crystals with Suppressed Ion Migration for High‐Performance Planar‐Type Photodetectors

2D Dion-Jacobson (DJ) perovskites have recently drawn much attention owing to their superior charge transport and high environmental stability. Unfortunately, their intrinsic optoelectronic properties are largely unexplored due to the lack of high-quality single crystals available for accurate measurements. Herein, a reactive, low-temperature-gradient crystallization process to grow high-quality 2D perovskite single crystal (BDAPbI4 ) using symmetric straight chain 1,4-butanediammonium as a short-chain insulating spacer is developed. It is found that the BDAPbI4 single crystal exhibits a direct bandgap with effective charge collection (μτ = 1.45 × 10-3 cm2 V-1 ). In particular, the BDAPbI4 single crystal shows a high ion migration activation energy (0.88 eV) that is desired for stability. Moreover, the planar-type photodetectors made of BDAPbI4 single crystals demonstrate excellent photoresponse performance, including large dynamic linear range (150 dB), high responsivity (927 mA W-1 ), fast response speed, and exceptional stability. Theoretical calculations reveal that the enhanced carrier transport properties are mainly attributed to the interlayer-induced coupling of the inorganic layers. Furthermore, the rigid structure of BDAPbI4 , resulting from the strong hydrogen bonds between the organic cations and the inorganic framework, will result in both low defect density and low ion migration, leading to superior carrier transport properties and detection performance.

The improved photoresponse properties of self-powered NiO/ZnO heterojunction arrays UV photodetectors with designed tunable Fermi level of ZnO

Self-powered ultraviolet (UV) photodetectors (PDs) based on ZnO heterojunctions have attracted more attention due to the simple preparation and excellent photoresponse performance without any power supply. The self-powered UV PDs based on NiO nanoflakes/ZnO nanorod arrays (NRs) heterojunctions were fabricated by a low-cost, simple chemical bath deposition (CBD) method. The crystal quality, optical and electronic properties of ZnO NRs is modified by Al3+ ions additions in the precursor solution. The heterojunction devices with ZnO NRs grown in 0.5% Al3+ ions additions precursor solution exhibit a narrow UV spectral selectivity, high photoresponsivity R (85.12 mA/W) and detectivity D* (1.74 × 1012 cm·Hz1/2/W) and a fast response speed (~2 ms) under 378 nm UV light for low intensity irradiance (0.2 mW/cm2) at zero bias. The large built-in electric field of the NiO/ZnO heterojunction with the increased Fermi level of ZnO NRs provide a strong driving force to separate and transfer the photo-generated carriers, decrease the recombination of the carriers and then improve the photoresponse performance of heterojunction devices without external bias.

A Highly Sensitive Single Crystal Perovskite-Graphene Hybrid Vertical Photodetector.

Organolead trihalide perovskites have attracted significant attention for optoelectronic applications due to their excellent physical properties in the past decade. Generally, both grain boundaries in perovskite films and the device structure play key roles in determining the device performance, especially for horizontal-structured device. Here, the first optimized vertical-structured photodetector with the perovskite single crystal MAPbBr3 as the light absorber and graphene as the transport layer is shown. The hybrid device combines strong photoabsorption characteristics of perovskite and high carrier mobility of flexible graphene, exhibits excellent photoresponse performance with high photoresponsivity (≈1017.1 A W-1 ) and high photodetectivity (≈2.02 × 1013 Jones) in a low light intensity (0.66 mW cm-2 ) under the actuations of 3 V bias and laser irradiation at 532 nm. In particular, an ultrahigh photoconductive gain of ≈2.37 × 103 is attained because of fast charge transfer in the graphene and large recombination lifetime in the perovskite single crystal. The vertical architecture combining perovskite crystal with highly conductive graphene offers opportunities to fulfill the synergistic effect of perovskite and 2D materials, is thus promising for developing high-performance electronic and optoelectronic devices.

A flower-inspired divergent light-trapping structure with quasi-spherical symmetry towards a high-performance flexible photodetector.

Molybdenum disulfide (MoS2) has received widespread attention in recent years due to its exciting properties. However, the practical applications of MoS2 in optoelectronic devices are impeded by the power supply problem, the lack of flexibility, and the low light absorption for planar nanosheets and nanosheet arrays. Inspired by the elaborate architecture of the flower Tagetes erecta L., in this work, a self-assembled divergent MoS2 nanoflower (MoS2_F) with quasi-spherical symmetry is successfully synthesized by a facile one-step hydrothermal method. It is of significance that coupled with asymmetric silver electrodes and packaged by polymethyl methacrylate (PMMA), a self-powered flexible photodetector (PD) based on MoS2_F is actualized and shows an excellent flexible photoresponse performance at zero bias voltage. The divergent structure with quasi-spherical symmetry enables the MoS2_F to achieve strong broadband and omnidirectional absorption (92.7%) and ensures that the MoS2_F maintains the same physical contact on a different bending degree. Intriguingly, excellent flexibility and stability have been achieved as MoS2_F PD retains 91.4% of the initial efficiency even when bent to 151° and retains 92.5% of the initial efficiency even after 1000 bending cycles. Therefore, by a low-cost process, this work demonstrates an innovative avenue to fabricate a self-powered flexible photodetector with excellent light absorption, broadband response, flexibility, and stability, which is of great practical significance for optoelectronic applications in various environments.