Heterostructure-based Photodetectors Research Articles

Ultrasensitive Near-Infrared Polarization Photodetectors with Violet Phosphorus/InSe van der Waals Heterostructures.

Near-infrared (NIR) polarization photodetectors with two-dimensional (2D) semiconductors and their van der Waals (vdW) heterostructures have presented great impact for the development of a wide range of technologies, such as in the optoelectronics and communication fields. Nevertheless, the lack of a photogenerated charge carrier at the device's interface leads to a poor charge carrier collection efficiency and a low linear dichroism ratio, hindering the achievement of high-performance optoelectronic devices with multifunctionalities. Herein, we present a type-II violet phosphorus (VP)/InSe vdW heterostructure that is predicted via density functional theory calculation and confirmed by Kelvin probe force microscopy. Benefiting from the type-II band alignment, the VP/InSe vdW heterostructure-based photodetector achieves excellent photodetection performance such as a responsivity (R) of 182.8 A/W, a detectivity (D*) of 7.86 × 1012 Jones, and an external quantum efficiency (EQE) of 11,939% under a 1064 nm photon excitation. Furthermore, the photodetection performance can be enhanced by manipulating the device geometry by inserting a few layers of graphene between the VP and InSe (VP/Gr/InSe). Remarkably, the VP/Gr/InSe vdW heterostructure shows a competitive polarization sensitivity of 2.59 at 1064 nm and can be integrated as an image sensor. This work demonstrates that VP/InSe and VP/Gr/InSe vdW heterostructures will be effective for promising integrated NIR optoelectronics.

Improved liquid phase exfoliation technique for the fabrication of MoS2/graphene heterostructure-based photodetector

2D nanosheets produced using liquid phase exfoliation method offers scalable and cost effective routes to optoelectronics devices. But this technique sometimes yields high defect, low stability, and compromised electronic properties. In this work, we employed an innovative approach that improved the existing liquid phase exfoliation method for fabricating MoS2/graphene heterostructure-based photodetector with enhanced optoelectronic properties. This technique involves hydrothermally treating MoS2 before dispersing it in a carefully chosen and environmentally friendly IPA/water solvent for ultrasonication exfoliation through an optomechanical approach. Thereafter, heterostructure nanosheets of MoS2 and graphene were formed through sequential deposition technique for the fabrication of vertical heterojunctions. Furthermore, we achieved a vertically stacked MoS2/graphene photodetector and a bare MoS2 photodetector. The MoS2/graphene hybrid nanosheets were characterized using spectroscopic and microscopic techniques. The results obtained show the size of the nanosheets is between 350 and 500 nm on average, and their thickness is less than or equal to 5 nm, and high crystallinity in the 2H semiconducting phase. The photocurrent, photoresponsivity, external quantum efficiency (EQE), and specific detectivity of MoS2/graphene heterostructure at 4 V bias voltage and 650 nm illumination wavelength were 3.55 μA, 39.44 mA/W, 7.54 %, and 2.02 × 1010 Jones, respectively, and that of MoS2 photodetector are 0.55 μA, 6.11 mA/W, 1.16 %, and 3.4 × 109 Jones. The results presented indicate that the photoresponse performances of the as-prepared MoS2/graphene were greatly improved (about 7-fold) compared to the photoresponse of the sole MoS2. Again, the MoS2/graphene heterostructure fabricated in this work show better optoelectronic characteristics as compared to the similar heterostructure prepared using the conventional solution processed method. The results provide a modest, inexpensive, and efficient method to fabricate heterojunctions with improved optoelectronic performance.

High-performance visible-near-infrared photodetector based on the N2200/Sb2Se3 nanorod arrays organic-inorganic hybrid heterostructure.

Antimony selenide (Sb2Se3) is a suitable candidate for a broadband photodetector owing to its remarkable optoelectronic properties. Achieving a high-performance self-powered photodetector through a desirable heterojunction still needs more efforts to explore. In this work, we demonstrate a broadband photodetector based on the hybrid heterostructure of Sb2Se3 nanorod arrays (NRAs) absorber and polymer acceptor (P(NDI2OD-T2), N2200). Owing to the well-matched energy levels between N2200 and Sb2Se3, the recombination of photogenerated electrons and holes in N2200/Sb2Se3 hybrid heterostructure is greatly inhibited. The photodetector can detect the wavelength from 405 to 980 nm, and exhibit high responsivity of 0.39 A/W and specific detectivity of 1.84 × 1011 Jones at 780 nm without bias voltage. Meanwhile, ultrafast response rise time (0.25 ms) and fall time (0.35 ms) are obtained. Moreover, the time-dependent photocurrent of this heterostructure-based photodetector keeps almost the same value after the storge for 40 days, indicating the excellent stability and reproducibility. These results demonstrate the potential application of a N2200/Sb2Se3 NRAs heterojunction in visible-near-infrared photodetectors.

Alternating BiI3-BiI van der Waals Photodetector with Low Dark Current and High-Performance Photodetection.

The emerging two-dimensional (2D) van der Waals (vdW) materials and their heterostructures hold great promise for optoelectronics and photonic applications beyond strictly lattice-matching constraints and grade interfaces. However, previous photodetectors and optoelectronic devices rely on relatively simple vdW heterostructures with one or two blocks. The realization of high-order heterostructures has been exponentially challenging due to conventional layer-by-layer arduous restacking or sequential synthesis. In this study, we present an approach involving the direct exfoliation of high-quality BiI3-BiI heterostructure nanosheets with alternating blocks, derived from solution-grown binary heterocrystals. These heterostructure-based photodetectors offer several notable advantages. Leveraging the "active layer energetics" of BiI layers and the establishment of a significant depletion region, our photodetector demonstrates a significant reduction in dark current compared with pure BiI3 devices. Specifically, the photodetector achieves an extraordinarily low dark current (<9.2 × 10-14 A at 5 V bias voltage), an impressive detectivity of 8.8 × 1012 Jones at 638 nm, and a rapid response time of 3.82 μs. These characteristics surpass the performance of other metal-semiconductor-metal (MSM) photodetectors based on various 2D materials and structures at visible wavelengths. Moreover, our heterostructure exhibits a broad-band photoresponse, covering the visible, near-infrared (NIR)-I, and NIR-II regions. In addition to these promising results, our heterostructure also demonstrated the potential for flexible and imaging applications. Overall, our study highlights the potential of alternating vdW heterostructures for future optoelectronics with low power consumption, fast response, and flexible requirements.

Low T direct plasma assisted growth of graphene on sapphire and its integration in graphene/MoS2 heterostructure-based photodetectors

We report on outstanding photo-responsivity, R > 103 A/W, fast response (~0.1 s), and broadband sensitivity ranging from the UV to the NIR in two terminal graphene/MoS2 photodetectors. Our devices are based on the deterministic transfer of MoS2 on top of directly grown graphene on sapphire, and their performance outperforms previous similar photodetectors using large-scale grown graphene. Here we devise a protocol for the direct growth of transparent (transmittance, Tr > 90%), highly conductive (sheet resistance, R□ < 1 kΩ) uniform and continuous graphene films on sapphire at 700 °C by using plasma-assisted chemical vapor deposition (CVD) with C2H2/H2 gas mixtures. Our study demonstrates the successful use of plasma-assisted low-temperature CVD techniques to directly grow graphene on insulators for optoelectronic applications.

Multicolor sensing of organic-inorganic hybrid heterostructure: From visible to invisible colors

Photodetection of organic-inorganic hybrid heterostructures from visible to invisible ultraviolet and infrared rays is revisited with respect to their material properties aspect, device structure, and emerging applications. The approach of organic-inorganic hybrid heterostructures using two or more varied materials has been extensively attempted as the emergence of broadband photodetection covering multi-colors as well as ultraviolet to infrared rays has ignited considerable interest in new applications. This review provides a timely overview of the scientific relationship between materials engineering and incident light properties, a systematic classification of representative material combinations, and a particular focus on each principle's insights. We also summarize recently-presented applications in organic-inorganic hybrid heterostructure-based photodetectors according to the target light wavelength.

Strong light-matter interaction and antireflection functionality of f-TiO2/GaN heterostructure broadband photodetector

Recent research focusing on broadband photodetectors offers a diverse range of applications like civilian, military, medical, etc. However, the available broadband photodetectors unable to retain high state-of-art performance parameters when operating at wide bandwidth. Herein, we report a broadband photodetector based on fibrils like TiO2 (f−TiO2) and GaN heterostructure. The TiO2 thin film has a high density of photo-generated charge carriers due to its great light absorption, antireflective, and highly oxidizing properties. These features of TiO2 enable a considerable increase in photocurrent for f−TiO2/GaN heterostructures compared to bare GaN, which provided a massive gain in the figure-of-merit performance metrics of f−TiO2/GaN-based devices. The fabricated f−TiO2/GaN device exhibits excellent optoelectronic characteristics, such as high responsivity (3.4 × 104 AW−1), outstanding external quantum efficiency (1.2 × 107 %), and detectivity (2.4 × 1012 Jones) under a weak optical signal of 90 nW. The design heterostructure-based photodetector also noticeably responds to illumination between the wavelengths of 250 nm and 780 nm. Additionally, TiO2 exhibits antimicrobial surface behavior, making it the best choice for pervasive biological and medical applications. Thus, TiO2/GaN heterostructure-based device like environmental screening, agriculture, medicine, and biodefense have proven their immense versatility in next-generation sequencing technology, medical science, cutting-edge crops, and creating interactive environments.

High-Sensitivity 2D MoS2/1D MWCNT Hybrid Dimensional Heterostructure Photodetector

A photodetector based on a hybrid dimensional heterostructure of laterally aligned multiwall carbon nanotubes (MWCNTs) and multilayered MoS2 was prepared using the micro-nano fixed-point transfer technique. Thanks to the high mobility of carbon nanotubes and the efficient interband absorption of MoS2, broadband detection from visible to near-infrared (520-1060 nm) was achieved. The test results demonstrate that the MWCNT-MoS2 heterostructure-based photodetector device exhibits an exceptional responsivity, detectivity, and external quantum efficiency. Specifically, the device demonstrated a responsivity of 3.67 × 103 A/W (λ = 520 nm, Vds = 1 V) and 718 A/W (λ = 1060 nm, Vds = 1 V). Moreover, the detectivity (D*) of the device was found to be 1.2 × 1010 Jones (λ = 520 nm) and 1.5 × 109 Jones (λ = 1060 nm), respectively. The device also demonstrated external quantum efficiency (EQE) values of approximately 8.77 × 105% (λ = 520 nm) and 8.41 × 104% (λ = 1060 nm). This work achieves visible and infrared detection based on mixed-dimensional heterostructures and provides a new option for optoelectronic devices based on low-dimensional materials.

Layered Heterostructures Based on MoS2/MoSe2 Nanosheets Deposited on GaN Substrates for Photodetector Applications

Due to the advanced properties of layered 2D materials, their heterostructuring with conventional 3D semiconductors is one of the promising ways to design efficient and affordable optoelectronic devices. However, systematic studies on designing 2D/3D heterojunctions with a focus on enhancing the photodetection properties are sparse in the literature. In this report, we present systematic experimental and theoretical investigations on 2D MoS2/MoSe2 heterostructuring with modified GaN substrates for designing efficient photodetectors. We achieved a gradual increment in photocurrent by engineering MoS2 and MoSe2 as single/double heterojunctions on GaN substrates. Time-correlated single-photon counting (TCSPC) results infer significant improvement in the lifetimes of the photoexcited charge carriers for the optimized MoS2/MoSe2/e-GaN heterostructure-based photodetectors. Interestingly, photodetectors designed with double heterojunctions that maintain type-II band alignment (e-GaN/MoSe2/MoS2) exhibit the highest photoresponsivity of 82 A/W, specific detectivity of 1.79 ×1014 Jones, external quantum efficiency of 27,880%, and stability for over 6 months in a laboratory testing environment under the illumination of 365 nm. Density functional theory (DFT) simulations establish the superiority of double heterojunctions with staircase band alignment for efficient charge carrier transport. This study provides fundamental insights on optimizing the band alignment for desired photodetection concerning 2D/3D integration, which can be exploited for other hybrid integrated systems and applications.

Ultrasensitive, Highly Repeatable, Ultrafast MoO3/P-Si Heterostructure-Based Photodetector

This article presents the development of an ultrasensitive molybdenum trioxide/porous silicon (MoO3/P-Si) heterostructure-based photodetector. Process scalability, high speed, higher detectivity, and repeatability are the key parameters of the demonstrated efficient photodetector. The P-Si and MoO3 nanoflakes (NFs) are synthesized by anodization and oxidation of RF-sputtered Mo thin film at 500 °C, respectively. The proposed MoO3/P-Si photodetector exhibits a high photo-to-dark current ratio (PDCR) in the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 4\times 10^{{2}}$ </tex-math></inline-formula> and a lower dark current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {d}}$ </tex-math></inline-formula> ). In addition, the MoO3/P-Si device exhibits a significantly improved photoresponsivity of 2.1 A/W and a detectivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$9.1\times 10^{{11}}$ </tex-math></inline-formula> Jones compared with the other photodetectors (P-Si and MoO3). The MoO3/P-Si heterojunction-based photodetector shows <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 4$ </tex-math></inline-formula> times improved detectivity than P-Si and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 14$ </tex-math></inline-formula> times improved detectivity than MoO3. Moreover, the device shows an ultrafast rise/fall times (0.09/0.05 s) with excellent stability and repeatability. These results demonstrate a high-performance and highly repeatable photodetector based on MoO3/P-Si heterojunction. The excellent performance of MoO3/P-Si heterojunction indicates that it has great application prospects in the field of visible photodetectors.

Surface/Interface Defect Engineering on Charge Carrier Transport toward Broadband (UV-NIR) Photoresponse in the Heterostructure Array of p-Si NWs/ZnO Photodetector

The surface/interface properties, especially interfacial states, have a key impact on overall carrier generation, recombination/transport, and/or collection proficiency for heterostructure-based photodetectors. This study demonstrates the significant enhancement of ultraviolet–near infrared (UV-NIR) (300–1100 nm) broadband photodetection in the heterostructure array of p-Si NWs/ZnO photodetectors with engineering of surface/interface charge carrier transportation under different processing conditions. In the case of a pulsed laser deposition (PLD)-grown photodetector, coupling of the subsidiary value of the defect state with the interfacial layer (Si–O–Zn) at the p–n junction reduces the charge carrier recombination, resulting in a large enhancement of transient photocurrent in the visible (Vis)–NIR region. However, in the case of a chemical solution deposition (CSD)-grown photodetector, plenty of oxygen vacancies (Vos) become the trap-assisted recombination centers by capturing of photoinduced carriers. The average value of responsivity (R) at 1 V bias for the PLD-grown detector is ∼5.5 A/W in the Vis–NIR (500–1100 nm) region, whereas in the UV region (≤375 nm), the value of R reached ∼8 A/W. The value of R in the PLD-grown detector is enhanced ∼102 folds in the UV region and ∼20 folds in the Vis–NIR region in comparison with the CSD-grown detector. Further, carrier generation, trapping, and transport/recombination processes in the surface/interface are well illustrated to explain the dynamics of the charge carrier contributing to the photoresponse behavior in the UV-NIR broadband region.

Two dimensional NbSe2/Nb2O5 metal-semiconductor heterostructure-based photoelectrochemical photodetector with fast response and high flexibility.

Two dimensional (2D) metal-semiconductor heterostructures are promising for high-performance optoelectronic devices due to fast carrier separation and transportation. Considering the superior metallic characteristics accompanied by high electrical conductivity in NbSe2, surface oxidation provides a facile way to form NbSe2/Nb2O5 metal-semiconductor heterostructures. Herein, size-dependent NbSe2/Nb2O5 nanosheets were achieved by a liquid phase exfoliation method and a gradient centrifugation strategy. These NbSe2/Nb2O5 heterostructure-based photodetectors show high responsivity with 23.21 μA W-1, fast response time of millisecond magnitude, and wide band detection ability in the UV-Vis region. It is noticeable that the photocurrent density is sensitive to the surface oxygen layer due to the oxygen-sensitized photoconduction mechanism. The flexible testing of the NbSe2/Nb2O5 heterostructure-based PEC-type photodetectors exhibits high photodetection performance even after bending and twisting. Beyond that, the solid-state PEC-type NbSe2/Nb2O5 photodetector also achieves relatively stable photodetection and high stability. This work promotes the application of 2D NbSe2/Nb2O5 metal-semiconductor heterostructures in flexible optoelectronic devices.

A waveguide-integrated self-powered van der Waals heterostructure photodetector with high performance at the telecom wavelength.

Two-dimensional (2D) materials are attractive candidates for high-performance photodetectors due to their wide operating wavelength and potential to integrate with silicon photonics. However, due to their limited atomic thickness and short carrier lifetime, they suffer from high driving source-drain voltages, weak light-matter interactions and low carrier collection efficiency. Here, we present a high-performance van der Waals (vdWs) heterostructure-based photodetector integrated on a silicon nitride photonic platform combining p-type black phosphorus (BP) and n-type molybdenum disulfide (MoS2). Owing to the efficient carrier separation process and dark current suppression at the junction interface of the vdWs heterostructure, high photodetectivity and a fast response speed can be achieved. A fast response time (∼2.08/3.54 μs), high responsivity (11.26 mA W-1), and a high light on/off ratio (104) operating in the near-infrared telecom band are obtained at zero bias. Our research highlights the great potential of the high-efficiency waveguide-integrated vdWs heterojunction photodetector for integrated optoelectronic systems, such as high-data-rate interconnects operated at standardized telecom wavelengths.

Photodetection Properties of MoS2, WS2 and MoxW1-xS2 Heterostructure: A Comparative Study.

Layered transition metals dichalcogenides such as MoS2 and WS2 have shown a tunable bandgap, making them highly desirable for optoelectronic applications. Here, we report on one-step chemical vapor deposited MoS2, WS2 and MoxW1-xS2 heterostructures incorporated into photoconductive devices to be examined and compared in view of their use as potential photodetectors. Vertically aligned MoS2 nanosheets and horizontally stacked WS2 layers, and their heterostructure form MoxW1-xS2, exhibit direct and indirect bandgap, respectively. To analyze these structures, various characterization methods were used to elucidate their properties including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and high-resolution transmission electron microscopy. While all the investigated samples show a photoresponse in a broad wavelength range between 400 nm and 700 nm, the vertical MoS2 nanosheets sample exhibits the highest performances at a low bias voltage of 5 V. Our findings demonstrate a responsivity and a specific detectivity of 47.4 mA W-1 and 1.4 × 1011 Jones, respectively, achieved by MoxW1-xS2. This study offers insights into the use of a facile elaboration technique for tuning the performance of MoxW1-xS2 heterostructure-based photodetectors.

Self-powered, ultra-fast and high photoresponsivity of MoTe2/HfSe2 heterostructure broadband photovoltaic device

Due to their multifunctionality and tunable properties in electronic devices, the transition-metal dichalcogenides (TMDs) based van der Waals (vdW) heterostructures have attracted much attention and are considered a potential candidate for advanced nanoelectronics. In this work, a self-powered molybdenum ditelluride (MoTe2)/hafnium diselenide (HfSe2) vdW heterostructure-based photodetector with ohmic contacts is designed. The high rectification ratio is attained as 1.9×106, rising from the clean interface and small barrier height. Photovoltaic experiments are also carried out using laser light with a wavelength of 532–1064 nm in visible and near-infrared (VNIR) regions with different power intensities ranging from 10 to 120 nW. The photoresponsivity of MoTe2/HfSe2 is enhanced remarkably up to 1.3×103A/W with detectivity 2.6 × 1013 Jones and external quantum efficiency of 68% because of band-to-band and interlayer TMDs charge transition at a longer wavelength (1064 nm). Under incoming light with an intensity of 120 nW, rapid growth (6.8 μs) and decay times (8.7 μs) are projected because of interlayer TMDs charge transition at the longer wavelength. The obtained results showed significantly higher values than the reported vdW heterostructures. The fast response time, low recombination rate and astonishing value of photoresponsivity are the key parameters to developing highly efficient TMDs-based solar devices.

Rational Design of WSe2 /WS2 /WSe2 Dual Junction Phototransistor Incorporating High Responsivity and Detectivity.

The excellent semiconducting properties and ultrathin morphological characteristics allow van der Waals (vdW) heterostructures based on 2D materials to be promising channel materials for the next-generation optoelectronic devices, especially in photodetectors. Although various 2D heterostructure-based photodetectors have been developed, the unavoidable trade-off between responsivity and detectivity remains a critical issue for these devices. Here, an ingenious phototransistor based on WSe2 /WS2 /WSe2 dual-vdW heterostructures is constructed, performing both high responsivity and detectivity. In the charge neutrality point (gate voltage of -15V and bias voltage of 1V), this device demonstrates a pronounced photosensitivity, accompanying with high detectivity of 1.9×1014 Jones, high responsivity of 35.4AW-1 , and fast rise/fall time of 3.2/2.5ms at 405nm with power density of 60µWcm-2 . Density functional theory calculations, energy band profiles, and optoelectronic characteristics jointly verify that the high performance is ascribed to the distinctive device design, which not only facilitates the separation of photogenerated carriers but also produces a strong photogating effect. As a feasible application, an automotive radar system is demonstrated, proving that the device has considerable potential for application in vehicle intelligent assisted driving.

Electrically Modulated Wavelength-Selective Photodetection Enabled by MoS2/ZnO Heterostructure

Regardless of the significant progress in photodetectors (PDs), most conventional technologies are equipped with optical filters for spectral discrimination, which results in expensive circuitry as well as a high incidence of energy loss. Different from traditional PDs, a ${\mathrm{Mo}\mathrm{S}}_{2}/\mathrm{Zn}\mathrm{O}$ heterostructure-based PD is demonstrated that exhibits a bias-dependent switchable spectral response. A low-band-gap ${\mathrm{Mo}\mathrm{S}}_{2}$ thin film is vertically stacked on top of a high-band-gap $\mathrm{Zn}\mathrm{O}$ film that allows selective charge transport from each layer by modulating the applied bias, resulting in a fine discrimination between visible and near-infrared (NIR) light. Under a lower applied bias, a dominant photoresponse in the visible region by the $\mathrm{Zn}\mathrm{O}$ film is observed, whereas an enhanced response in the NIR region is obtained at higher bias, which is attributed to the generation of charge carriers in the ${\mathrm{Mo}\mathrm{S}}_{2}$ region. The excellent figures of merit obtained in the study attest to the high quality of the device, paving the way for fabricating energy-efficient imaging systems free of optical filters.

Atomically thin WSe2 nanosheets for fabrication of high-performance p-Si/WSe2 heterostructure

Optoelectronic devices based on two-dimensional transition metal dichalcogenides (2D-TMDC) are picking up a great interest by providing broadband photoresponse, environmental stability, and durability. The direct band gap of a monolayer of TMDC upon exfoliation enhances light absorption in the visible spectrum with pure to heterostructures form of TMDC, in turn, makes it more reliable for photodetection applications. Herein, we report a facile way to synthesize WSe2 nanosheets by solvothermal synthesis method for fabrication of large-area p-Si/WSe2 heterostructure-based photodetector. The structural, compositional, and morphological investigation asserted that prepared WSe2 nanosheets have atomically thin behavior and crystalline nature with 2H-polymorph. Moreover, the prepared p-Si/WSe2 photodiode presents promising features such as notable quick response time, high photoresponsivity of 1.15 A/W, detectivity of 1011 Jones, and external quantum efficiency of 134%, enduring for a long-time span under illumination. Thus, p-Si/WSe2 heterostructure embarks on the forefront in the development of high-performance optoelectronic device fabrication.

Two-Dimensional Cs2AgBiBr6/WS2 Heterostructure-Based Photodetector with Boosted Detectivity via Interfacial Engineering.

Two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers have been widely used for optoelectronic devices because of their ultrasensitivity to light detection acquired from their direct gap properties. However, the small cross-section of photon absorption in the atomically thin layer thickness significantly limits the generation of photocarriers, restricting their performance. Here, we integrate monolayer WS2 with 2D perovskites Cs2AgBiBr6, which serve as the light absorption layer, to greatly enhance the photosensitivity of WS2. The efficient charge transfer at the Cs2AgBiBr6/WS2 heterojunction is evidenced by the shortened photoluminescence (PL) decay time of Cs2AgBiBr6. Scanning photocurrent microscopy of Cs2AgBiBr6/WS2/graphene reveals that improved charge extraction from graphene leads to an enhanced photoresponse. The 2D Cs2AgBiBr6/WS2/graphene vertical heterostructure photodetector exhibits a high detectivity (D*) of 1.5 × 1013 Jones with a fast response time of 52.3 μs/53.6 μs and an on/off ratio of 1.02 × 104. It is worth noting that this 2D heterostructure photodetector can realize self-powered light detection behavior with an open-circuit voltage of ∼0.75 V. The results suggest that the 2D perovskites can effectively improve the TMDC layer-based photodetectors for low-power consumption photoelectrical applications.

WSe2/MoS2 van der Waals Heterostructures Decorated with Au Nanoparticles for Broadband Plasmonic Photodetectors

Surface plasmons of metal nanostructures can resonantly enhance the light absorption of two-dimensional (2D) materials and stacked van der Waals (vdW) heterostructure-based photodetectors, realizing the improvement of responsivity. So far, it has remained challenging to control and tune surface plasmons via artificially varying the geometry of arrayed metal nanostructures. Here, we demonstrate a broadband plasmonic photodetector based on an integration of gold nanoparticles (Au NPs) on a WSe2/MoS2 vdW heterostructure. The plasmon resonance peaks could be tuned by the artificially patterning of Au NPs with the geometry controlled by a rapid thermal processing technique and enable a great improvement of light absorption crossing broadband spectral regimes from 400 to 1100 nm. Our device operates at room temperature and exhibits the highest responsivity of up to 1948 mA W–1, detectivity of 7.2 × 1011 cm Hz1/2 W–1, and the ultrafast response of 8.3 μs under an illumination with zero-bias voltage. These merits of high-performance detection and rapidly scalable production of controlled metal nanostructures, with the development of 2D material synthesis and transfer techniques, offer great potential for large-area and smart fabrication of nanoscale optoelectronic devices with low power consumption.