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In this work, we report on a sensitive wavelength sensor composed geometrically of an individual PdTe2/thin Si/PdTe2 heterojunction that is able to quantitatively discriminate incident light wavelengths spanning from the deep-ultraviolet to the near-infrared spectrum. The prominent photovoltaic activity of the heterojunction endows the device with the ability to work in the absence of extrinsic power supply. Owing to the wavelength-dependent optical absorption characteristics as well as the distance-related charge carrier recombination behavior, the heterojunction device exhibits deep contrast in the distribution of photo-generation rate relative to the junction area and different recombination activities in photocarriers, upon light irradiation with varied wavelengths from opposite directions. As a consequence, it shows completely different spectral photoresponses in front-illuminated and back-illuminated modes. Therefore, the corresponding photocurrent ratio of the device versus incident light wavelength can be numerically depicted through a monotone function, via which one can accurately discriminate the wavelength spanning from 265 to 1050 nm with an average absolute error of below 10 nm. This work paves an effective avenue for developing highly sensitive wavelength sensors, which hold enormous promise in future photoelectrical devices and systems. [ABSTRACT FROM AUTHOR]

A hybrid heterostructure composed of two-dimensional (2D) material/narrow bandgap semiconductor represents a promising platform for designing highly efficient and cost-effective near-infrared (NIR) photodetectors. However, performance enhancement is usually restricted by reduced light usage due to relatively high refractive indexes and low absorption coefficients of the hybrid heterostructures. Herein, we demonstrate that a quasi-2D perovskite thin film can serve well as an antireflection coating to greatly boost the performance of a multilayered PdTe2/Ge heterostructure-based NIR photodetector. Specifically, upon the perovskite coating with an optimized thickness, photoresponsivity and specific detectivity can be improved significantly from ∼526.4 mA W−1 to ∼976.2 mA W−1 and from ∼2.43 × 1011 Jones to ∼4.78 × 1011 Jones, respectively, under a 1550 nm optical communication wavelength with a light intensity of ∼70 μW cm−2 at zero bias. Meanwhile, other important performance parameters including dark current and response speed can maintain almost identical. Moreover, owing to the improved moisture resistance of the upper quasi-2D perovskite layer, the photodetector exhibits excellent device stability and operational durability under atmospheric conditions. The results not only provide a convenient route for improving the performance of NIR optoelectronic devices but also broaden the application scope of perovskite materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A γ-In2Se3/Si heterostructure phototransistor with a broadened photoresponse has been developed, presenting a responsivity, specific detectivity and response speed of 10.24 A W−1, 8.63 × 1012 Jones and 0.76/0.85 ms (rise time/fall time) at 450 nm, respectively. The high responsivity could be attributed to the depressed dark current of the γ-In2Se3 nanofilm and the high gain arising from the gating effect of the phototransistor. Further analysis reveals that the relatively high responsivity and fast response speed facilitate the application of the device in real-time and accurate health monitoring, such as heart rate detection. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, a sensitive near-infrared (NIR) photodetector based on a CsBi3I10 perovskite/Si heterojunction is developed by directly coating a layer of inorganic perovskite onto a planar Si substrate. The as-constructed heterojunction displays a representative current rectifying behavior in the dark and remarkable photoresponse properties upon light irradiation. The distinct photovoltaic effect enables the device to function as a self-driven photodetector working at zero bias. Furthermore, it is observed that the photodetector is sensitive in a wide spectral region with peak sensitivity at ∼820 nm. Under 808 nm illumination, the critical photoresponse parameters of responsivity, external quantum efficiency and specific detectivity reached 178.7 mA W−1, 27.2% and 4.99 × 1010 Jones at zero bias, respectively, which can be further increased to as high as 492.1 mA W−1, 75.2% and 1.38 × 1011 Jones at a working bias of −1 V. What is more, the present device also holds a large Ilight/Idark ratio of ∼1 × 104, a rapid response speed of 73/36 μs, and excellent air stability even after 3 months of storage under ambient conditions. Considering the good photoresponse performance and facile assembly approach, the CsBi3I10 perovskite/Si heterojunction possesses huge potential for future cost-effective and high-performance photodetection applications. [ABSTRACT FROM AUTHOR]