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High‐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. [ABSTRACT FROM AUTHOR]

Cost-effective and highly efficient near-infrared photodetectors are urgently demanded in many electronic and optoelectronic products for applications in both military and civil areas. Herein, by using a simple solution-based drop-casting technique, we fabricate a Ti3C2Tx MXene/Ge two-dimensional/three-dimensional van der Waals heterostructure, which can function well as a highly efficient near-infrared photodetector. When shined by 1550 nm light illumination, the heterostructure exhibits an apparent photovoltaic effect and can, thus, work as a self-driven near-infrared photodetector. A representative photodetector achieves a photocurrent responsivity of ∼314.3 mA W−1 at zero bias voltage, which can be improved to as high as ∼642.6 mA W−1 by applying a small reverse bias voltage of −1 V. In addition, other critical performance parameters such as current on/off ratio, specific detectivity, and response speed are estimated to be ∼430, ∼2.01 × 1011 Jones, and 17.6/13.6 μs, respectively. The excellent device performance is comparable to that of many previously reported two-dimensional material/Ge heterostructure-based near-infrared photodetectors, which cannot be constructed using facile solution-based processes. This work provides a facile avenue for developing high-performance and low-cost near-infrared photodetectors, which will find important applications in future optoelectronic systems. [ABSTRACT FROM AUTHOR]

Deep-ultraviolet (DUV) photodetection has garnered extensive research interest for its vital applications in many military and civil fields. In this work, we present the synthesis of a large-area two-dimensional (2D) PdTe2 multilayer, which can be directly transferred onto a GaN substrate to construct a vertical heterostructure for visible-blind DUV photodetection. Upon 265 nm light irradiation, the heterostructure displays a distinct photovoltaic behavior, enabling it to serve as a self-driven photodetector. The important photoresponse parameters, such as ${I}_{light}/{I}_{dark}$ ratio, responsivity, specific detectivity and DUV/visible (265 nm/450 nm) rejection ratio reach as high as 106, 168.5 mA/W, $5.3 \times 10^{12}$ Jones, and 104, respectively, at zero bias. The responsivity can be further enhanced to 254.6 mA/W by applying a small reverse bias of −1.0 V. In addition, the photodetector can function as a DUV light image sensor to reliably record an “H” pattern with a decent resolution. The present study paves a way for designing high-performance cost-effective DUV photodetectors towards practical optoelectronic applications. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate the fabrication of a conformal CuO/Si microholes array heterojunction through the DC reactive magnetron sputtering from a high-purity Cu target. By using the monolayer graphene as the top electrode, the device served well as a self-powered vis-NIR photodetector, showing a high responsivity of 301.5 mA W−1, specific detectivity of $7.96\times 10^{12}$ Jones and a fast response speed (rise time $9.9~\mu $ s and fall time $10~\mu \text{s}$) upon 530 nm illumination. Compared to its planar counterpart, the responsivity was remarkably enhanced over the broadband region. The underlying reason should be ascribed to the improved light trapping in the microholes via the longitudinal Fabry-Perot (F-P) cavity resonance, according to theoretical simulation by finite-difference time-domain (FDTD) solution. Such an effect gave rise to an enhanced light-matter interaction, leading to the improved photoresponse. This work also opens up an effective way for the on-chip high performance photodetection due to the well compatibility with the current complementary metal-oxide-semiconductor (CMOS) technology. [ABSTRACT FROM AUTHOR]

Photodetection at a wavelength of about 1060 nm is very important for applications including medical imaging, optical communication, and light detection and ranging. In this article, a self-powered near-infrared light detector with a narrowband at around 1060 nm is realized based on a simple Si Schottky structure, in which the Ohmic and Schottky electrodes are configured on the front and rear surfaces of the Si substrate, respectively. The as-assembled device exhibits a tunable peak response near 1060 nm with a full width at half maximum of 107 nm, which could be due to the combined effect of the narrow photo-current generation and the self-filtering effect of the silicon substrate. At zero bias, a specific detectivity of ~ 1 × 1011 Jones and linear dynamic range about 101 dB are achieved, in spite of the weak absorption of Si at this wavelength. The external quantum efficiency can be improved to 135% under a low bias of −1 V, indicating the existence of gain mechanism during photodetection. Finally, it is also found that the as-assembled near-infrared device shows excellent antiinterference capability during the photodetection process. These results corroborate that the present Si photodetector may find promising application in future near-infrared optoelectronic devices and systems. [ABSTRACT FROM AUTHOR]

In the past several years, organic–inorganic hybrid perovskites and all inorganic perovskites have attracted enormous research interest in a variety of optoelectronic applications including solar cells, light‐emitting diodes, semiconductor lasers, and photodetectors for their plenty of appealing electrical and optoelectrical properties. Benefiting from the inherent amplification function of transistors and the pronounced photogating effect, perovskite‐based phototransistors and hybrid photodetectors can provide very high photoresponsivity and gain, rendering them highly promising for some specific applications especially ultrasensitive light detection. A review on the recent progress of phototransistors and hybrid photodetectors using perovskites as light‐sensitive materials is presented. The efforts and development in 3D and 2D perovskite‐based phototransistors, and perovskite/functional material (e.g., graphene, 2D semiconductors, organic semiconductors, and other semiconductors) heterojunction‐based hybrid photodetectors are introduced and discussed systematically. Some processing techniques for optimizing device performance are also addressed. In the final section, a conclusion of the research achievements is presented and possible challenges as well as outlook are provided to guide future activity in this research field. [ABSTRACT FROM AUTHOR]

Abstract: Group‐10 layered transitional metal dichalcogenides including PtS2, PtSe2, and PtTe2 are excellent potential candidates for optoelectronic devices due to their unique properties such as high carrier mobility, tunable bandgap, stability, and flexibility. Large‐area platinum diselenide (PtSe2) with semiconducting characteristics is far scarcely investigated. Here, the development of a high‐performance photodetector based on vertically aligned PtSe2‐GaAs heterojunction which exhibits a broadband sensitivity from deep ultraviolet to near‐infrared light, with peak sensitivity from 650 to 810 nm, is reported. The Ilight/Idark ratio and responsivity of photodetector are 3 × 104 and 262 mA W−1 measured at 808 nm under zero bias voltage. The response speed of τr/τf is 5.5/6.5 µs, which represents the best result achieved for Group‐10 TMDs based optoelectronic device thus far. According to first‐principle density functional theory, the broad photoresponse ranging from visible to near‐infrared region is associated with the semiconducting characteristics of PtSe2 which has interstitial Se atoms within the PtSe2 layers. It is also revealed that the PtSe2/GaAs photodetector does not exhibit performance degradation after six weeks in air. The generality of the above good results suggests that the vertically aligned PtSe2 is an ideal material for high‐performance optoelectronic systems in the future. [ABSTRACT FROM AUTHOR]

As one of the most appealing two-dimensional materials, graphene (Gr) has attracted tremendous research interest in optoelectronic device applications for its plenty of exceptional electrical and optical properties. The emergence of Gr/semiconductor hybrid heterostructures provides a promising platform for assembling high-performance optoelectronic devices that can overcome intrinsic limitations of Gr. However, although significant achievements have been made, many challenges still exist. Here, we comprehensively review the progress in the development of various optoelectronic devices based on Gr/semiconductor hybrid heterostructures, including /group II-VI nanostructures, /group III-V semiconductors, /group IV semiconductors, /metal oxides and /other semiconductors, in terms of the device design, device performance and physics, processing techniques for performance optimization, etc . In the final section, conclusions of the existing techniques are presented and future challenges in optoelectronic applications of Gr/semiconductor hybrid heterostructures are addressed. [ABSTRACT FROM AUTHOR]

Following a significant number of graphene studies, other two-dimensional (2D) layered materials have attracted more and more interest for their unique structures and distinct physical properties, which has opened a window for realizing novel electronic or optoelectronic devices. Here, we present a comprehensive review on the applications of 2D-layered semiconductors as photodetectors, including photoconductors, phototransistors, and photodiodes, reported in the past five years. The device designs, mechanisms, and performances of the photodetectors are introduced and discussed systematically. Emerging techniques to improve device performances by enhancing light-matter interactions are addressed as well. Finally, we deliver a summary and outlook to provide a guideline of the future development of this rapidly growing field. [ABSTRACT FROM AUTHOR]

Schottky junctions made from a titanium dioxide nanotube (TiO2NT) array in contact with a monolayer graphene (MLG) film are fabricated and utilized for UV light detection. The TiO2NT array is synthesized by the anodization and the MLG through a simple chemical vapor deposition process. Photoconductive analysis shows that the fabricated Schottky junction photodetector (PD) is sensitive to UV light illumination with good stability and reproducibility. The corresponding responsivity ( R), photoconductive gain ( G), and detectivity ( D*) are calculated to be 15 A W−1, 51, and 1.5 × 1012 cm Hz1/2 W−1, respectively. It is observed that the fabricated PD exhibits spectral sensitivity and a simple power-law dependence on light intensity. Moreover, the height of the Schottky junction diode is derived to be 0.59 V by using a low temperature I-V measurement. Finally, the working mechanism of the TiO2NT array/MLG film Schottky junction PD is elucidated. [ABSTRACT FROM AUTHOR]

Photodetection in the solar‐blind deep‐ultraviolet (DUV) regime (200–280 nm) has received significant attention for its many critical applications in military and civil areas. In this study, a vapor–solid synthesis technique for catalyst‐free growth of single‐crystalline β‐Ga2O3 nanowires is developed. A photodetector made of the nanowires is highly sensitive to 265 nm DUV illumination with excellent photoresponse performance. The performance parameters including Ilight/Idark ratio, responsivity, specific detectivity and response speed can attain ≈103, ≈233 A W−1, ≈8.16 × 1012 Jones, and 0.48/0.04 s, respectively. Additionally, the detector has an abrupt response cutoff wavelength at ≈290 nm with a reasonable DUV/visible (250–405 nm) rejection ratio exceeding 102. It is also found that the device can operate properly at a large applied bias of 200 V with the responsivity being enhanced to as high as ≈1680 A W−1. Moreover, such a nanowires‐based photodetector can function as a DUV light image sensor with a reasonable spatial resolution. Holding the above advantages, the present DUV photodetector based on catalyst‐free grown β‐Ga2O3 nanowires possesses huge possibility for application in future DUV optoelectronics. [ABSTRACT FROM AUTHOR]

Combining both 1D geometry and the features of hybrid perovskite materials, perovskite micro/nanowires have recently attracted particular attention for a variety of optoelectronic device applications. Herein, by taking advantage of the strong built‐in potential induced by asymmetric contact with varied work functions, highly sensitive visible photodetectors based on a CH3NH3PbI3 microwire array that display pronounced photovoltaic activities are reported. These photodetectors afford the capability to work without an external power supply. A representative detector with Au/Ag electrodes achieves a reasonable responsivity of 161.1 mA W−1 with a fast response speed of 13.8/16.1 µs under 520 nm illumination at zero bias. In addition, such a device is also characterized by an ultralow dark current of tens of femtoamps, enabling a high specific detectivity of 1.3 × 1012 Jones. Furthermore, a flexible photodetector is successfully prepared, which shows comparable photoresponse performance and outstanding flexibility and bending durability. Given the good device performance and simple device geometry, the present self‐driven photodetectors hold great promise for future highly sensitive and low‐energy‐consumption photodetection systems. [ABSTRACT FROM AUTHOR]

Due to its significant applications in many relevant fields, light detection in the solar‐blind deep‐ultraviolet (DUV) wavelength region is a subject of great interest for both scientific and industrial communities. The rapid advances in preparing high‐quality ultrawide‐bandgap (UWBG) semiconductors have enabled the realization of various high‐performance DUV photodetectors (DUVPDs) with different geometries, which provide an avenue for circumventing numerous disadvantages in traditional DUV detectors. This article presents a comprehensive review of the applications of inorganic UWBG semiconductors for solar‐blind DUV light detection in the past several decades. Different kinds of DUVPDs, which are based on varied UWBG semiconductors including Ga2O3, MgxZn1−xO, III‐nitride compounds (AlxGa1−xN/AlN and BN), diamond, etc., and operate on different working principles, are introduced and discussed systematically. Some emerging techniques to optimize device performance are addressed as well. Finally, the existing techniques are summarized and future challenges are proposed in order to shed light on development in this critical research field. Recent advances in developing solar‐blind deep ultraviolet light (DUV) photodetectors based on various inorganic ultrawide‐bandgap semiconductors are reviewed, such as Ga2O3, MgxZn1−xO, III‐nitride compounds (AlxGa1−xN/AlN and BN), and diamonds. [ABSTRACT FROM AUTHOR]

Wafer‐scale palladium diselenide (PdSe2) films synthesized through a simple selenization method exhibit great potential for developing high‐performance photodetectors. As Lin‐Bao Luo, Zhong‐Jun Li, Yuen‐Hong Tsang, and co‐workers describe in article number 1806878, the as‐fabricated PdSe2/Si heterojunctions exhibit high responsivity, specific detectivity, and broadband response ranging from 200 to 3044 nm, which is further optimized by decorating it with black phosphorus quantum dots. [ABSTRACT FROM AUTHOR]

Palladium diselenide (PdSe2), a thus far scarcely studied group‐10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer‐scale and homogeneous 2D PdSe2 film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe2 with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe2 exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe2 layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W−1) and specific detectivity (≈1013 Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the as‐selenized PdSe2 is a promising material for optoelectronic application. This study reports on the wafer‐area synthesis of a high‐quality 2D palladium diselenide (PdSe2) layer through a simple selenization method. Both experimental analysis and theoretical simulation reveal that the PdSe2 film exhibits a gradual transition from a semiconductor (monolayer) to semimetal (bulk). Further combination of PdSe2 with Si leads to a fast and sensitive broadband photodiode, with a high responsivity and specific detectivity. [ABSTRACT FROM AUTHOR]