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In this study, simple-structured wavelength sensors were developed by depositing two back-to-back Au/MAPbI

A leaky mode resonance induced dual-band photodetector is fabricated using graphene/silicon nanowire array heterojunctions, which exhibit two peak responsivities at 430 nm and 660 nm.

In this work, we report on the synthesis of InSe nanobelts through a catalyst-free chemical vapor deposition (CVD) growth approach. A remarkable blue shift of the peak photoresponse was observed when the thickness of the InSe nanobelt decreases from 562 to 165 nm. Silvaco Technology Computer Aided Design (TCAD) simulation reveals that such a shift in spectral response should be ascribed to the wavelength-dependent absorption coefficient of InSe, for which incident light with shorter wavelengths will be absorbed near the surface, while light with longer wavelengths will have a greater penetration depth, leading to a red shift of the absorption edge for thicker nanobelt devices. Considering the above theory, three kinds of photodetectors sensitive to blue (450 nm), green (530 nm), and red (660 nm) incident light were achieved by tailoring the thickness of the nanobelts, which can enable the spectral reconstruction of a purple "H" pattern, suggesting the potential application of 2D layered semiconductors in full-color imaging.

This review provides an overview of the basic concepts and operation mechanisms of ultraviolet (UV) photodetectors (PDs), the main research status, and future outlooks of II–VI group compound semiconductor-based UVPDs.

Schematic diagram of the sensing mechanism of the UV-light-assisted PdSe2/InSe heterojunction sensor.

A schematic diagram of the device principle of a wavelength sensor consisting of two horizontally stacked MLG/Ge heterojunctions and the wavelength-dependent photocurrent ratio at different thicknesses of PD1.

In this study, we present a wavelength sensor that is capable of distinguishing the spectrum in the range from ultraviolet (UV) to near-infrared (NIR) light. The filterless device is composed of two horizontally stacking PdSe2/20 μm Si/PdSe2 heterojunction photodetectors with a photovoltaic (PV) behavior, which makes it possible for the device to work at 0 bias voltage. Due to the relatively small thickness of Si and the wavelength-dependent absorption coefficient, the two PdSe2/20 μm Si/PdSe2 photodetectors according to theoretical simulation display a sharp contrast in distribution of the photoabsorption rate. As a result, the photocurrents of both photodetectors evolve in completely different ways with increasing wavelengths, leading to a monotonic decrease in the photocurrent ratio from 6800 to 22 when the wavelength gradually increases from 265 to 1050 nm. The corresponding relationship between both the photocurrent ratio and wavelength can be easily described by the monotonic function, which can help to precisely determine the wavelength in the range from 265 to 1050 nm, with an average relative error less than ±1.6%. It is also revealed that by slightly revising the monotonic function, the wavelength in other different temperatures can also be estimated.

Palladium diselenide (PdSe2), a noble transition metal dichalcogenide has attracted increasing attention in recent years due to its outstanding semiconductor properties. In this study, 2D PdSe2 nanofilms with thicknesses ranging from 2 to 28 nm and their heterostructures with Si substrates (PdSe2/Si heterostructures) were synthesized via a simple selenization method. Electrical transport characterizations based on field-effect transistor devices indicate that the few-layer PdSe2 nanofilms exhibit a p-type semiconducting behavior. The optimal sensing performance of the PdSe2/Si-8 sensor (8 nm-thick PdSe2) exhibits a comparable response toward NO2 gas (ΔR/Ra = ∼7.2% to 100 ppb and ∼18% to 1 ppm) at room temperature (RT). This response may result from the heterostructure effect and maze-type surface. Additionally, the PdSe2/Si-8 sensor has selectivity toward NO2 compared with other gases including NO, H2, CO, NH3, and C2H5OH. Furthermore, density functional theory (DFT) calculations reveal the largest adsorption energy and charge transfer between NO2 and the PdSe2 surface, which coincides well with the experimental results. Moreover, the PdSe2/Si-8 sensor also exhibits repeatability and long-term stability during about 4 months at RT. These results indicate that the PdSe2/Si heterostructures may be a promising nanomaterial for room-temperature NO2 gas-sensing devices.

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.

Solar-blind deep-ultraviolet (DUV) photodetectors based on Ga2O3 have attracted great attention due to their potential applications for many military and civil purposes. However, the development of device integration for optoelectronic system applications remains a huge challenge. Herein, we report a facile method for patterned-growth of high-quality β-Ga2O3 thin films, which are assembled into a photodetectors array comprising 8 × 8 device units. A representative detector exhibits outstanding photoresponse performance, in terms of an ultra-low dark current of ∼0.62 pA, a large Ilight/Idark ratio exceeding 104, a high responsivity of ∼0.72 A W−1 and a decent specific detectivity of ∼4.18 × 1011 Jones, upon 265 nm DUV illumination. What is more, the DUV/visible (250/400 nm) rejection ratio is as high as 103 with a sharp response cut-off wavelength at ∼280 nm. Further optoelectronic analysis reveals that the photodetectors array has good uniformity and repeatability, endowing it the capability to serve as a reliable DUV light image sensor with a decent spatial resolution. These results suggest that the proposed technique offers an effective avenue for patterned growth of β-Ga2O3 thin films for multifunctional DUV optoelectronic applications.

Highly ordered perovskite nanowire (PNW) arrays are important building blocks for potential application in integrated optoelectronic devices due to their unique properties. Herein, a recordable digital versatile disk-assisted nanochannel-confined growth (NCG) strategy was developed for large-scale growth of different kinds of PNW arrays with preferentially crystallographic orientation on various substrates. Photodetector constructed from MAPbI3 NW arrays exhibits prominent photoresponse properties with a responsivity of 20.56 A W−1 and specific detectivity of 4.73 × 1012 Jones, respectively. What is more, the photodetector can function as a polarization-sensitive photodetector due to the crystallographic orientation of the one-dimensional PNW arrays, with a polarization ratio of 2.2. The proposed NCG strategy provides a cost-efficient and effective method for the fabrication of high-quality PNW arrays with potential applications in future integrated devices and systems.

Patterned growth of periodic perovskite film arrays is essential for application in sensing devices and integrated optoelectronic systems. Herein, we report on patterned growth of addressable perovskite photodetector arrays through an uncured polydimethylsiloxane (PDMS) oligomer-assisted solution-processed approach, in which a periodic hydrophilic/hydrophobic substrate replicating the predesigned patterns of the PDMS stamp was formed due to the migration of uncured siloxane oligomers in the PDMS stamp to the intimately contacted substrate. By using this technique, MAPbI3 film photodetector arrays with neglectable pixel-to-pixel variation, a responsivity of 2.83 A W-1, specific detectivity of 5.4 × 1012 Jones, and fast response speed of 52.7/57.1 μs (response/recovery time) were achieved. An 8 × 8 addressable photodetector array was further fabricated, which functioned well as a real-time image sensor with reasonable spatial resolution. It is believed that the proposed strategy will find potential application in large-scale fabrication of other photodetector arrays, which might be potentially important for future integrated optoelectronic devices.

Two-dimensional layered (2D) materials are currently attracting intensive research interest for high-performance photodetection and other optoelectronic applications. However, the study of device integration for multifunctional optoelectronic applications is still at a nascent stage. Here, the assembly of a multilayered PtSe2/pyramid-Si heterostructure-based photodetector array consisting of 8 × 8 device units is demonstrated. Owing to the pronounced light confinement effect of the heterostructures, the devices present an prominent photovoltaic effect, which enables efficient self-driven photodetection in a broadband wavelength spectrum. The Ilight/Idark ratio, responsivity, external quantum efficiency (EQE) and specific detectivity can attain values as high as 5.51 × 106, 567 mA W−1, 87% and 1.26 × 1013 jones, respectively, upon 810 nm near-infrared (NIR) light illumination. What is more, benefiting from the large-scale homogeneous material growth technique, the photodetector array exhibits excellent uniformity and repeatability in photoresponse performance with negligible unit-to-unit variation. The above characteristics provide the photodetector array with the capability of recording a simple image produced by NIR illumination and monitoring a moving photonic signal, showing the great possibility for NIR image sensing and light trajectory tracking applications.

A wavelength sensor as a representative optoelectronic device plays an important role in many fields including visible light communication, medical diagnosis, and image recognition. In this study, a wavelength-sensitive detector with a new operation mechanism was reported. The as-proposed wavelength sensor which is composed of two parallel PtSe2/thin Si Schottky junction photodetectors is capable of distinguishing wavelength in the range from ultraviolet to near infrared (UV-NIR) light (265 to 1050 nm), in that the relationship between the photocurrent ratio of both photodetectors and incident wavelength can be numerically described by a monotonic function. The unique operation mechanism of the thin Si based wavelength sensor was unveiled by theoretical simulation based on Synopsys Sentaurus Technology Computer Aided Design (TCAD). Remarkably, the wavelength sensor has an average absolute error of ±4.05 nm and an average relative error less than ±0.56%, which are much better than previously reported devices. What is more, extensive analysis was performed to reveal how and to what extent the working temperature and incident light intensity, and the thickness of the PtSe2 layer will influence the performance of the wavelength sensor.

In this work, we present the construction of a multilayered PtSe2/Ge heterostructure-based photodetector array comprising 1 × 10 device units operating in the short-wavelength infrared (SWIR) spectrum region. The as-fabricated heterostructures show an obvious photovoltaic effect, providing the devices with the ability to work as self-driven photodetectors. Upon 1550 nm illumination, a typical photodetector exhibits prominent photoresponse performance with the current on/off ratio, responsivity, external quantum efficiency and specific detectivity reaching 1.08 × 103, 766 mA W−1, 61.3% and 1.1 × 1011 Jones, respectively. The device also has a fast response speed with rise/fall times of 54.9 μs/56.6 μs. Thanks to the respectable homogeneity in device performance, the photodetector array can reliably record an image of a “diode symbol” produced by SWIR irradiation. What is more, the photodetector is successfully integrated into a SWIR optical communication system serving as an optical receiver to transmit a text signal. The above results imply a huge possibility of the present heterostructure-based photodetector array for some optoelectronic purposes such as SWIR image sensing and optical communication applications.

Multispectral photodetection has garnered enormous research interest and has always been challenging to date. Here, we present the realization of an electrically adjusted single-band/dual-band photodetector based on an inorganic lead-free halide Cs3Cu2I5/two-dimensional (2D) PdTe2 multilayer/Ge multiheterostructure. Owing to its unique optical property and distinct carrier transport behaviour, the device can be easily converted from a single-band photodetector operating in the near-infrared (NIR) region to a dual-band photodetector working in both deep-ultraviolet (DUV) and NIR regimes, upon applying a reverse bias voltage. Significantly, the device shows a peak responsivity of ∼694.1 mA W−1 at 1550 nm at zero bias, and maximum responsivity values of ∼744.2 mA W−1 and ∼712.5 mA W−1 at 265 nm and 1550 nm, respectively, at a small reverse bias. This characteristic also endows the photodetector with an excellent DUV/NIR dual-band optical imaging capability. This work will offer a new opportunity for designing high-performance photodetectors with multiple functionalities operating in complicated circumstances.

We present the first report of a water-regulated method for obtaining a cubic-phase CsPbBr3 single crystal that could be frozen at low temperature with a CsBr/PbBr2 ratio of 1 : 1. The cubic CsPbBr3 single-crystal photodetector exhibits a superior responsivity of 278 A W−1, an EQE of 6.63 × 104%, and an ultrahigh detectivity of 4.36 × 1013 Jones under low-power 520 nm irradiation at 3 V.

In this paper, the authors report the fabrication of a sensitive deep ultraviolet (DUV) photodetector by using an individual GaSe nanobelt with a thickness of 52.1 nm, which presents the highest photoresponse at 265 nm illumination with a responsivity and photoconductive gain of about 663 A W

In this study, we have developed a high-sensitivity, near-infrared photodetector based on PdSe2/GaAs heterojunction, which was made by transferring a multilayered PdSe2 film onto a planar GaAs. The as-fabricated PdSe2/GaAs heterojunction device exhibited obvious photovoltaic behavior to 808 nm illumination, indicating that the near-infrared photodetector can be used as a self-driven device without external power supply. Further device analysis showed that the hybrid heterojunction exhibited a high on/off ratio of 1.16×105 measured at 808 nm under zero bias voltage. The responsivity and specific detectivity of photodetector were estimated to be 171.34 mA/W and 2.36×1011 Jones, respectively. Moreover, the device showed excellent stability and reliable repeatability. After 2 months, the photoelectric characteristics of the near-infrared photodetector hardly degrade in air, attributable to the good stability of the PdSe2. Finally, the PdSe2/GaAs-based heterojunction device can also function as a near-infrared light sensor.

Platinum telluride (PtTe2) has garnered significant research enthusiasm owing to its unique characteristics. However, large-scale synthesis of PtTe2 toward potential photoelectric and photovoltaic application has not been explored yet. Herein, we report direct tellurization of Pt nanofilms to synthesize large-area PtTe2 films and the influence of growth conditions on the morphology of PtTe2. Electrical analysis reveals that the as-grown PtTe2 films exhibit typical semimetallic behavior, which is in agreement with the results of first-principles density functional theory (DFT) simulation. Moreover, the combination of multilayered PtTe2 and Si results in the formation of a PtTe2/Si heterojunction, exhibiting an obvious rectifying effect. Moreover, the PtTe2-based photodetector displays a broadband photoresponse to incident radiation in the range of 200-1650 nm, with the maximum photoresponse at a wavelength of ∼980 nm. The R and D* of the PtTe2-based photodetector are found to be 0.406 A W-1 and 3.62 × 1012 Jones, respectively. In addition, the external quantum efficiency is as high as 32.1%. On the other hand, the response time of τrise and τfall is estimated to be 7.51 and 36.7 μs, respectively. Finally, an image sensor composed of a 8 × 8 PtTe2-based photodetector array was fabricated, which can record five near-infrared (NIR) images under 980 nm with a satisfying resolution. The result demonstrates that the as-prepared PtTe2 material will be useful for application in NIR optoelectronics.

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 $\sim 1\times 10^{11}$ 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.

Lead halide perovskites have received much attention in the field of optoelectronic devices. However, the environment-unfriendly nature and intrinsic instability of these perovskites hamper their commercial applications. In this work, one novel one-dimensional lead-free halide perovskite with high stability, CsCu2I3, was prepared via an antisolvent-assisted crystallization method. The prepared CsCu2I3 bears a high exciton binding energy of ∼105 meV and a high photoluminescence quantum yield of 12.3%. We fabricated a deep ultraviolet photodetector based on a CsCu2I3 film that is nearly blind to 405 nm visible light but is sensitive to 265 and 365 nm illumination. The device exhibits excellent reproducibility and a high Ilight/Idark ratio of 22 under 265 nm illumination. Furthermore, the responsivity, specific detectivity, and external quantum efficiency are as high as 22.1 mA/W, 1.2 × 1011 Jones, and 10.3% under a light density of 0.305 mW/cm2, respectively. These findings demonstrate that CsCu2I3 perovskites should have great potential for future optoelectronics.

Photonic detection with narrow spectrum selectivity is very important to eliminate the signal from obtrusive light, which can improve the anti-interference ability of the infrared imaging system. While the self-driving effect inherent to the p-n junction is very attractive in optic-electronic integration, the application of the p-n junction in narrow-band photodetectors is limited by the usual broad absorption range. In this work, a self-powered filterless narrowband near-infrared photodetector based on CuGaTe2/silicon p-n junction was reported. The as-fabricated photodetector exhibited typical narrow-band response which shall be ascribed to the slightly smaller band gap of Si than CuGaTe2 and the restricted photocurrent generation region in the p-n heterojunction by optimizing CuGaTe2 thickness. It is observed that when the thickness of CuGaTe2 film is 143 nm, the device exhibits a response peak centered around 1050 nm with a full-width at half-maximum of ∼118 nm. Further device analysis reveals a specific detectivity of ∼1012 Jones and a responsivity of 114 mA/W under 1064 nm illumination at zero bias. It was also found that an image system based on the narrowband CuGaTe2/Si photodetector showed high noise immunity for its spectral selective characteristics.

GaSe microbelts were successfully synthesized using Ga/Ga2Se3 as the precursor mixture, where excess Ga was required to serve as the metal catalyst. Meanwhile, a spontaneously oxidized surface amorphous oxide (GaOx) layer formed, which induced a built-in electric field perpendicular to the surface. Benefiting from this effect, a GaSe microbelt-based photodetector attained a high responsivity of ∼3866 A W−1 and a photoconductive gain of up to ∼1.06 × 104. This study sheds light on the controlled synthesis of microstructures and provides a device design concept for high-performance micro/nano optoelectronics.

In this work, we present the assembly of a γ-In2Se3/GaAs heterostructure-based photodetector linear array composed of 1 × 10 device units. The layered γ-In2Se3 films with a well-defined pattern are deposited directly onto a planar GaAs substrate via radio-frequency (RF) magnetron sputtering deposition assisted by a pre-photolithography process. The as-fabricated heterojunction exhibits an apparent photovoltaic effect, which endows the device with a function to operate as a self-driven photodetector. The critical photoresponse performance parameters in terms of the Ilight/Idark ratio, responsivity (R), specific detectivity (D*) and response speed can reach 1.29 × 104, 0.25 A W−1, 7.34 × 1012 Jones and 23.6/146.7 μs (rise/fall times), respectively, upon 660 nm light irradiation at 0 V. What is more, further device evaluation reveals that the photodetector array shows good uniformity with a minor unit-to-unit variation. The above merits endow the photodetector array with the ability to monitor a moving optical signal and to record an “E” image produced by visible illumination. It is believed that the present photodetector array is very promising for some optoelectronic purposes such as real-time light trajectory tracking and visible light image sensing applications.

A wavelength sensor as a representative optoelectronic device plays an important role in many fields including visible light communication, medical diagnosis, and image recognition. In this study, a wavelength-sensitive detector with a new operation mechanism was reported. The as-proposed wavelength sensor which is composed of two parallel PtSe

Ultraviolet photodetectors (UVPDs) based on wide band gap semiconductors (WBSs) are important for various civil and military applications. However, the relatively harsh preparation conditions and the high cost are unfavorable for commercialization. In this work, we proposed a non-WBS UVPD by using a silicon nanowire (SiNW) array with a diameter of 45 nm as building blocks. Device analysis revealed that the small diameter SiNW array covered with monolayer graphene was sensitive to UV light but insensitive to both visible and infrared light illumination, with a typical rejection ratio of 25. Specifically, the responsivity, specific detectivity, and external quantum efficiency under 365 nm illumination were estimated to be 0.151 A/W, 1.37 × 1012 Jones, and 62%, respectively, which are comparable to or even better than other WBS UVPDs. Such an abnormal photoelectrical characteristic is related to the HE1m leaky mode resonance (LMR), which is able to shift the peak absorption spectrum from near-infrared to UV regions. It is also revealed that this LMR is highly dependent on the diameter and the period of the SiNW array. These results show narrow band gap semiconductor nanostructures as promising building blocks for the assembly of sensitive UV photodetectors, which are very important for various optoelectronic devices and systems.

In this study, we present a wavelength sensor that is capable of distinguishing the spectrum in the range from ultraviolet (UV) to near-infrared (NIR) light. The filterless device is composed of two horizontally stacking PdSe

We present the first report of a water-regulated method for obtaining a cubic-phase CsPbBr3 single crystal that could be frozen at low temperature with a CsBr/PbBr2 ratio of 1 : 1. The cubic CsPbBr3 single-crystal photodetector exhibits a superior responsivity of 278 A W-1, an EQE of 6.63 × 104%, and an ultrahigh detectivity of 4.36 × 1013 Jones under low-power 520 nm irradiation at 3 V.

Solar-blind deep ultraviolet photodetectors (DUVPDs) based on conventional inorganic ultrawide bandgap semiconductors (UWBS) have shown promising application in various civil and military fields and yet they can hardly be used in wearable optoelectronic devices and systems for lack of mechanical flexibility. In this study, we report a non-UWBS solar-blind DUVPD by designing ultrathin polymer nanofibrils with a virtual ultrawide bandgap, which was obtained by grafting P3HT with PHA via a polymerization process. Optoelectronic analysis reveals that the P3HT-b-PHA nanofibrils are sensitive to DUV light with a wavelength of 254 nm but are virtually blind to both 365 nm and other visible light illuminations. The responsivity is 120 A/W with an external quantum efficiency of up to 49700%, implying a large photoconductive gain in the photoresponse process. The observed solar-blind DUV photoresponse is associated with the resonant mode due to the leakage mode of the ultrathin polymer nanofibrils. Moreover, a flexible image sensor composed of 10 × 10 pixels can also be fabricated to illustrate their capability for image sensing application. These results signify that the present ultrathin P3HT-b-PHA nanofibrils are promising building blocks for assembly of low-cost, flexible, and high-performance solar-blind DUVPDs.

In this work, a sensitive deep ultraviolet (DUV) light photodetector based on inorganic and lead-free Cs3Cu2I5 crystalline film derived by a solution method was reported. Optoelectronic characterization revealed that the perovskite device exhibited nearly no sensitivity to visible illumination with wavelength of 405 nm but exhibited pronounced sensitivity to both DUV and UV light illumination with response speeds of 26.2/49.9 ms for rise/fall time. The Ilight/Idark ratio could reach 127. What is more, the responsivity and specific detectivity were calculated to be 64.9 mA W-1 and 6.9 × 1011 Jones, respectively. In addition, the device could keep its photoresponsivity after storage in air environment for a month. It is also found that the capability of Cs3Cu2I5 crystalline film device can readily record still DUV image with acceptable resolution. The above results confirm that the DUV photodetector may hold great potential for future DUV optoelectronic device and systems.

We reported a novel integrated portable human blood system based on absorption photometry and microfluidic technology. A capillary pump for fluid control was embedded in microfluidic chip instead of heavy syringe pump. The analytes could automatically flow, mix and react in chip. It achieves long-term stability of hydrophilic microfluidic channel surface for rapid and sensitive detection. Herein, we detected three analytes from human blood, including triglyceride (TGL), albumin (ALB) and total protein (TP) which are very important for health examination. All components of this system including light-emitting diode (LED) light source, microfluidic chip, photodiode detector (PD), electronic circuit, Organic LED screen and memory card were fully integrated into a portable instrument with small size (11.2 × 7.2 × 6.1 cm). The pair of LED and PD was used for measuring light absorbance of biochemical assay. The limit of detections (LODs) for TGL, ALB and TP were estimated to be below 0.1 mmol/L, 4 g/L and 10 g/L respectively, which is significantly below the clinical cut-off value. Passing − Boblok regression analyses were used to achieve the evaluation for this system. It showed good accuracy and feasibility of our system and was expected to be useful as a potential clinical tool for human blood serum test.

We present the first report of a new suspension method for obtaining cubic MAPbBr3 single crystal with a concave surface. The cubic MAPbBr3 crystal with microconcavity possesses good crystallinity and carrier lifetime. Excellent photoelectric performance was provided by the concavity-based MAPbBr3 photodetectors because of the good light trapping and shortened carrier pathway. As a result, the concavity-based photodetector exhibits superior responsivity of 62.9 and 5.43 A W–1 and EQE of 1.50 × 104% and 1.30 × 103% under low-power and high-power 520 nm irradiation of 3.67 μW cm–2 and 35.4 mW cm–2 at 3 V, respectively, which are more than 500% higher than those of the plane-based photodetector. In particular, the concavity-based photodetector has an ultrahigh detectivity of 6.5 × 1012 Jones at ultralow power of 3.67 μW cm–2, which is 6.5 times higher than that of the planar device.

Light detection in the near-infrared (NIR) region is of particular importance due to its wide application for both military and civil purposes. In this study, we fabricated high-performance NIR photodetectors by simply transferring a multilayered PtSe2 film onto a Ge wafer to form vertical hybrid heterojunctions. These heterojunctions exhibit an apparent photovoltaic effect under NIR illumination, offering our devices the opportunity to operate without an external power supply. Based on further optoelectronic analysis, it was found that the devices were highly sensitive to the 1300, 1550, 1650 and even 2200 nm NIR illumination with good reproducibility and long-term air stability. Under the 1550 nm irradiation, the NIR photodetectors attained the high responsivity and specific detectivity of 602 mA W−1 and 6.3 × 1011 Jones, respectively, along with fast response speed of 7.4/16.7 μs at zero bias. Due to the excellent photoresponse performance and the simple device geometry, the present self-driven NIR photodetectors are very promising for application in future optoelectronic devices and systems.

In this study, we report on the synthesis of layered γ-In2Se3 for broadband photodetector and near infrared light image sensing applications. The layered γ-In2Se3 nanofilm with a thickness of around 74 nm was deposited onto a n-Si wafer through radio frequency magnetron sputtering. It is found that the as-assembled γ-In2Se3/n-Si shows an obvious photovoltaic behavior and can work properly as a self-powered broadband photodetector over a wide range of wavelengths (200–2200 nm). Such a unique spectral response beyond the absorption limit of both intrinsic γ-In2Se3 and n-Si can be ascribed to the existence of defect energy levels between the valence band and the conduction band, as a result of Se substitution of In atoms according to theoretical simulation based on first-principles calculations. Specifically, the γ-In2Se3/n-Si photodetector has a responsivity of 0.57 A W−1, a specific detectivity of 2.6 × 1012 Jones and a fast response speed (35/115 μs for τr/τf) under 808 nm light illumination, respectively, which are slightly better or comparable to other devices with similar geometries. Lastly, it was revealed that the γ-In2Se3/n-Si heterojunction photodetector can function as an effective near infrared (NIR) light image sensor with a decent spatial resolution, which suggests the great potential of the current device in future NIR optoelectronic systems.