Broadband Photodetector Research Articles

PdSe2/2H-MoTe2 Heterojunction Self-Powered Photodetector: Broadband Photodetection and Linear/Circular Polarization Capability.

In this research, we introduce a PdSe2/2H-MoTe2 heterojunction photodetector that exhibits both broadband self-powered photodetection and linear/circular polarization detection capabilities. It has a broad spectral response range (covering 375-2200 nm) and reaches a peak sensitivity at 532 nm, exhibiting a notable responsivity of 7.3 × 103 A/W and a substantial specific detectivity of 8.5 × 1012 Jones. Even in the near-infrared region of 1310 nm, it still has a high responsivity of 20 A/W. The self-powered photodetection capabilities of the PdSe2/2H-MoTe2 heterojunction are equally impressive, covering a broad range from 375 to 1550 nm, with a responsivity of 243 mA/W, a specific detectivity of 6.46 × 1010 Jones, a fill factor of 0.8, and an external quantum efficiency of 56.73%. Finally, simultaneous implementation of linear/circular polarization detection on the PdSe2/2H-MoTe2 heterojunction provides a powerful solution for near-infrared full-Stokes polarization detectors with high integration, miniaturization, and portability.

Tailored Environment-Friendly Reverse Type-I Colloidal Quantum Dots for a Near-Infrared Optical Synapse and Artificial Vision System.

Colloidal quantum dots (QDs) are emerging as potential candidates for constructing near-infrared (NIR) photodetectors (PDs) and artificial optoelectronic synapses due to solution processability and a tunable bandgap. However, most of the current NIR QDs-optoelectronic devices are still fabricated using QDs with incorporated harmful heavy metals of lead (Pb) and mercury (Hg), showing potential health and environment risks. In this work, we tailored eco-friendly reverse type-I ZnSe/InP QDs by copper (Cu) doping and extended the photoresponse from the visible to NIR region. Transient absorption spectroscopy analysis revealed the presence of Cu dopant states in ZnSe/InP:Cu QDs that facilitated the extraction of photogenerated charge carriers, leading to an enhanced photodetection performance. Specifically, under 400 nm illumination, the Cu-doped ZnSe/InP QDs-based PDs presented a broadband photodetection ranging from ultraviolet (UV) to NIR, with a responsivity of 70.5 A W-1 and detectivity of 2.8 × 1011 Jones, surpassing those of the undoped ZnSe/InP QDs-based PDs (49.4 A W-1 and 1.9 × 1011 Jones, respectively). More importantly, the ZnSe/InP:Cu QDs-PDs demonstrated various synapse-like characteristics of short-term plasticity (STP), long-term plasticity (LTP), and learning-forging-relearning under NIR light illumination, which were further used to construct PD array devices for simulating the artificial visual system that is available in prospective optical neuromorphic applications.

Multifunctional optoelectronic devices based on two-dimensional tellurium/MoS2 heterojunction

Two-dimensional van der Waals heterojunctions consisted of p–n-type semiconductors have been rapidly developed owing to their built-in electric field which can facilitate the separation of photogenerated electron–hole pairs and properties like current rectification and negative differential transconductance. Benefitting from these advantages, we have prepared an air-stable multifunctional p-tellurium (Te)/n-MoS2 heterostructure working both as a self-driven broadband photodetector and as an optically switchable complementary metal-oxide-semiconductor inverter. For photodetection, this device exhibits wavelength-modulated positive/negative optical response with large responsivity (1.51 A/W at 520 nm and 642.92 mA/W at 1550 nm, Vds = 0 V) and fast response speed, showcasing its prospects for optical encoding communication. Moreover, the device has been demonstrated to function as an inverter that will be shut down by illumination. Our multifunctional device possesses the compactness of integrated modules, widens the application scope of Te-based heterojunctions, and provides a reference for the application of Te-based devices in the field of integrated circuits.

Room-temperature infrared photoluminescence and broadband photodetection characteristics of Ge/GeSi islands on silicon-on-insulator.

In this study, molecular beam epitaxial growth of strain-driven three-dimensional self-assembled Ge/GeSi islands on silicon-on-insulator (SOI) substrates, along with their optical and photodetection characteristics, have been demonstrated. The as-grown islands exhibit a bimodal size distribution, consisting of both Ge and GeSi alloy islands, and show significant photoluminescence (PL) emission at room temperature, specifically near optical communication wavelengths. Additionally, these samples were used to fabricate a Ge/GeSi islands/Si nanowire (NW) based phototransistor using a typical e-beam lithography process. The fabricated device exhibited broadband photoresponse characteristics, spanning a wide wavelength range (300-1600 nm) coupled with superior photodetection characteristics and relatively low dark current (~ tens of pA). The remarkable photoresponsivity of the fabricated device, with a peak value of ~11.4 A/W (λ ~ 900 nm) in the near-infrared (NIR) region and ~ 1.36 A/W (λ ~ 1500 nm) in the short-wave infrared (SWIR) region, is a direct result of the photoconductive gain exceeding unity. The room-temperature optical emission and outstanding photodetection performance, covering a wide spectral range from the visible to the SWIR region, showcased by the single layer of Ge/GeSi islands on SOI substrate, highlight their potential towards advanced applications in broadband infrared Si-photonics and imaging. These capabilities make them highly promising for cutting-edge applications compatible with complementary metal-oxide-semiconductor (CMOS) technology.

Highly DUV to NIR-II responsive broadband quantum dots heterojunction photodetectors by integrating quantum cutting luminescent concentrators

Low-cost, high-performance, and uncooled broadband photodetectors (PDs) have potential applications in optical communication etc., but it still remains a huge challenge to realize deep UV (DUV) to the second near-infrared (NIR-II) detection for a single broadband PD. Herein, a single PD affording broadband spectral response from 200 to 1700 nm is achieved with a vertical configuration based on quantum dots (QDs) heterojunction and quantum cutting luminescent concentrators (QC–LC). A broadband quantum dots heterojunction as absorption layer was designed by integrating CsPbI3:Ho3+ perovskite quantum dots (PQDs) and PbS QDs to realize the spectral response from 400 to 1700 nm. The QC–LC by employing CsPbCl3:Cr3+, Ce3+, Yb3+, Er3+ PQDs as luminescent conversion layer to collect and concentrate photon energy for boosting the DUV–UV (200–400 nm) photons response of PDs by waveguide effect. Such broadband PD displays good stability, and outstanding sensitivity with the detectivity of 3.19 × 1012 Jones at 260 nm, 1.05 × 1013 Jones at 460 nm and 2.23 × 1012 Jones at 1550 nm, respectively. The findings provide a new strategy to construct broadband detector, offering more opportunities in future optoelectronic devices.

High performance self-driven broadband photodetector for polarized imaging based on novel ZrS3/ReSe2 van der Waals heterojunction

The distinctive characteristics of anisotropic two-dimensional (2D) materials, including in-plane anisotropy of optical absorption and carrier mobility, render them exceptionally suitable for application in the field of polarization detection and as a novel platform for the polarization imaging. Meanwhile, the consolidation of diverse functionalities within a single photodetector is highly anticipated to meet the demands of some special scenarios. Herein, a novel ZrS3/ReSe2 van der Waals (vdWs) heterostructure device was successfully constructed to realize polarization-sensitive, self-powered, and broadband photodetection and imaging. Owing to the built-in electric field of the type-II band alignment within the heterojunction, the device achieves a self-powered photoresponse ranging from 300 to 980 nm, an ultralow dark currentt ∼1 pA, and a commendable rise/decay time of 0.35/0.28 ms. Additionally, it has been demonstrated that the self-driven photodetector possesses a polarization-sensitivity with a notable anisotropic ratio about 2.02 (1.98) under 490 nm (980 nm) light illumination with zero bias, coupled with an excellent repeatability and stability. Furthermore, we also demonstrate the polarization imaging capabilities of the device in visible and near-infrared spectrum, realizing a contrast-enhanced degree of linear polarization imaging. This work paves a new platform to develop heterojunction photodetectors for high performance polarization-sensitive photodetection and next-generation polarized imaging.

Highly responsive MoS2/MoO3 heterojunction based broadband photodetector

Broadband photodetection finds indispensable utility across a spectrum of applications, spanning optical communication, spectrum switching, and memory storage. In this work, we demonstrate the fabrication of a heterojunction-based broadband photodetector using visible-infrared activated molybdenum disulfide (MoS2) and ultraviolet-responsive molybdenum trioxide (MoO3). The MoO3-x thin films were grown at room temperature using DC sputtering techniques, and subsequent annealing at varied temperatures mitigated defects, increased crystallinity, and produced stoichiometric MoO3 thin films. Through the sulphurisation of MoO3 via the chemical vapour deposition (CVD) technique, a heterojunction of transition metal oxide/transition metal dichalcogenide between MoO3 and MoS2 is developed. The heterostructure device exhibits broad spectral responsivity, ranging from ultraviolet A to short-wave infrared regions. In particular, ultraviolet ray incidence yields a maximum responsivity of 0.34 A W−1, a minimum noise equivalent power of 1.36 × 10−11 W Hz−1/2, and a maximum quantum efficiency of 119 %. Conversely, under infrared ray illumination, the device achieves a peak responsivity of 13.85 A W−1, a minimum noise equivalent power of 2.89 × 10−13 W Hz−1/2, and the highest quantum efficiency of 1618 %. The ensuing investigations hold promise for advancing heterojunction-based broadband photodetection applications.

Large area, ultrafast, suppressed dark current and high-performance PtSe2/MoS2 van der Waals heterostructure based visible to NIR broadband photodetector

Group-10 transitional metal dichalcogenide, in particular Platinum selenide (PtSe2), have attracted substantial attention owing to its fascinating properties such as high carrier mobility, narrow bandgap, and high stability in contrast to other low bandgap 2D materials. However, in bare PtSe2, high dark current and lower sensitivity restrict to make high-performance broadband photodetector. Herein, a large area and stable PtSe2/MoS2 heterostructure based photodetector is fabricated which exhibits suppressed dark current and high-performance with broad 400-1200 nm detection, covering visible to near-infrared region (NIR). The PtSe2/MoS2 heterostructure device exhibits ∼103 order reduction in the dark current, high detectivity, and better stable response as compared to its bare PtSe2 device. Moreover, under NIR (900 nm) illumination, the PtSe2/MoS2 device demonstrates high responsivity of 17.9 AW−1 and high specific detectivity of 9.8 × 1012 Jones at amoderate bias of −5V. It exhibits ultra-fast response with rise/ fall time of 103 μs/117 μs corroborating its high performance. To understand the working of PtSe2/MoS2 photodetector, a detailed carrier transport mechanism is investigated based on the interface. This work provides a facile strategy to fabricate large area, fast response and high-performance broadband photodetector to build future optoelectronic devices.

Achieving photomultiplication in organic-MOF complex via interface and band engineering

This work studies a hybrid broadband photodetector with and without metal–organic framework nanosheets with an inverted structure. It is observed that an inverted structure provides photomultiplication in the devices with both positive and negative biases. This phenomenon is believed to be due to a non-uniform TiO2/active layer interface where the porosity of TiO2 facilitates structural traps, in turn achieving photomultiplication in P3HT: PCBM (1:1) devices. Meanwhile, in photodetectors with an active layer of P3HT:ZnTCPP:PCBM (1:0.5:1), photomultiplication is attributed to interface traps and band alignment due to ZnTCPP nanosheets. The presence of ZnTCPP reduces the dip in EQE at 370–460 and 530–610 nm range, thus improving broadband detection (300–700 nm). Adding ZnTCPP to the devices results in improved rise and fall times. The on–off response is also relatively stable for the devices with ZnTCPP and has high detectivity (1011 Jones). Thus, this study sheds light on the role of a thin interface layer of TiO2 in photomultiplication and improving performance parameters with ZnTCPP nanosheets.

Patterned 3D-graphene for self-powered broadband photodetector

The remarkable ultra-wideband energy capabilities of zero-bandgap two-dimensional (2D) graphene have made it an outstanding material for photon absorption and charge carrier generation across a broad spectrum. However, atomically thick 2D-graphene only exhibits a light absorption efficiency of 2.3%, posing a challenge for graphene-based photodetectors to harness photon energy effectively. This study utilized plasma-enhanced chemical vapor deposition technology and a mask to create in situ patterned 3D-graphene/Si-based Schottky heterojunctions. The porous structure and natural nano-resonant cavities of the 3D-graphene enhanced the probability of light absorption, while the curved and sharp edges and corners of the patterned 3D-graphene concentrated the local electromagnetic field and induced localized surface plasmon resonance. Both theoretical and experimental analyses confirmed the improved light absorption mechanisms and charge transfer of photogenerated carriers under the built-in electric field. The photodetector based on the patterned 3D-graphene/Si Schottky structure exhibits excellent broadband response characteristics spanning from 380 to 1550 nm, with responsivity and specific detectivity of 68.47 A/W and 1.43 × 1012 Jones at a wavelength of 1550 nm. Furthermore, the photodetector demonstrated ultrafast microsecond-level response times (116/120 μs rise/fall times) along with exceptional stability and reliability. The potential applications of as-fabricated photodetector include logic devices such as “AND” and “OR” gates and information encryption. This research holds valuable scientific significance for the design of future optoelectronic devices and provides crucial insights and technical support for developing high-performance Si-based graphene detectors.

2D Reconfigurable Memtransistor for High‐Performance Dual‐Mode Memory and Broadband Photodetection

AbstractDeveloping multifunctional nanoelectronics will facilitate simplifying the circuits for future high‐integrated system. CuInP2S6 (CIPS) exhibiting ferroionic phenomena allows the manipulation of polarization and conductive behaviors. Here, a MoS2 transistor is fabricated with CIPS gate dielectric layer to realize the functions of nonvolatile memory, broadband photodetector and voltage comparator. It exhibited convex‐shaped anti‐ambipolar transfer characteristics, with a sharp boundary as the n‐/p‐type conductance conversion line, guiding the precise modulation of its working modes by tuning voltage. The CIPS works as a ferroelectric insulator to support the n‐type transistor, while as a semiconductor dominated by Cu+ migration to reconfigure a p‐type memristive transistor. It owns hysteresis behavior in both modes, demonstrating the n‐ and p‐type memory windows synchronously. Also, it exhibits the nonvolatile memory property with low energy‐consumption of 4 pJ per bite, good endurance of 2567 write‐erase cycles, and good retention with a high current on/off ratio of 2 × 103 over 104 s without any obvious decay. Moreover, it extends the photodetection from visible to near‐infrared with the responsivity of 321 AW−1 at 1200 nm wavelength. This work provides an effective strategy for the realization of multiple functions by specific materials and devices.

Oxidation-induced graded bandgap narrowing in Two-dimensional tin sulfide for high-sensitivity broadband photodetection

Two-dimensional (2D) layered group-IV monochalcogenides with large surface-to-volume ratio and high surface activity make that their structural and optoelectronic properties are sensitive to air oxidation. Here, we report the utilization of oxidation-induced gradient doping to modulate electronic structures and optoelectronic properties of 2D group-IV monochalcogenides by using SnS nanoplates grown by physical vapor deposition as a model system. By a precise control of oxidation time and temperature, the structural transition from SnS to SnSOx could be driven by the layer-by-layer oxygen doping and intercalation. The resulting SnSOx with a graded narrowing bandgap exhibits the enhanced optical absorption and photocurrent, leading to the fabricated SnSOx photodetector with remarkable photoresponsivity and fast response speed (<64 μs) at a broadband spectrum range of 520–1550 nm. The peak responsivity (7294 A/W) and detectivity (9.54 × 109 Jones) of SnSOx device are at least two orders of magnitude larger than those of SnS photodetector. Moreover, its photodetection performance can be competed with state-of-the-art of 2D materials-based photodetectors. This work suggests that the air oxidation could be utilized as an efficient strategy to engineer the electronic and optical properties of SnS and other 2D group-IV monochalcogenides for the development of high-performance broadband photodetectors.

Metasurface-enabled broadband multidimensional photodetectors

Light encodes multidimensional information, such as intensity, polarization, and spectrum. Traditional extraction of this light information requires discrete optical components by subdividing the detection area into many “one-to-one” functional pixels. The broadband photodetection of high-dimensional optical information with a single integrated on-chip detector is highly sought after, yet it poses significant challenges. In this study, we employ a metasurface-assisted graphene photodetector, enabling to simultaneously detect and differentiate various polarization states and wavelengths of broadband light (1-8 μm) at the wavelength prediction accuracy of 0.5 μm. The bipolar polarizability empowered by this design allows to decouple multidimensional information (encompassing polarization and wavelength), which can be achieved by encoding vectorial photocurrents with varying polarities and amplitudes. Furthermore, cooperative multiport metasurfaces are adopted and boosted by machine learning techniques. It enables precise spin-wavelength differentiation over an extremely broad wavelength range (1-8 μm). Our innovation offers a recipe for highly compact and high-dimensional spectral-polarization co-detection.

Investigation of Graphene Single Layer on P-Type and N-Type Silicon Heterojunction Photodetectors.

Photodetectors are of great interest in several technological applications thanks to their capability to convert an optical signal into an electrical one through light-matter interactions. In particular, broadband photodetectors based on graphene/silicon heterojunctions could be useful in multiple applications due to their compelling performances. Here, we present a 2D photodiode heterojunction based on a graphene single layer deposited on p-type and n-type Silicon substrates. We report on the electro-optical properties of the device that have been measured in dark and light conditions in a spectral range from 400 nm to 800 nm. The comparison of the device's performance in terms of responsivity and rectification ratio is presented. Raman spectroscopy provides information on the graphene single layer's quality and oxidation. The results showcase the importance of the doping of the silicon substrate to realize an efficient heterojunction that improves the photoresponse, reducing the dark current.

Enhancing broadband absorption and photocurrent generation in carbon dots via P3HT integration

The growing interest in carbon dots (CDs) arises from their diverse applications and unique properties. This study addresses challenges in CDs for photodetector (PD) applications, specifically surface defects and trap states hindering efficient charge transport. CDs/P3HT composites were prepared to overcome these issues by incorporating CDs in a poly(3-hexylthiophene) (P3HT) matrix. Broad absorption in spectroscopic characterization revealed its utility in fabricating a broadband PD. The CDs/P3HT PD displays a remarkable broadband photoresponse, spanning both UV and visible regions. The CDs and P3HT are effectively combined via non-covalent π-π interactions constituted by their conjugated systems. The π-π interaction increases electron delocalization and facilitates efficient charge transfer due to band alignment at the junction interface. Hence, fabricated CDs/P3HT PD demonstrated enhanced photocurrent compared to pure CDs, exhibiting high responsivity of 6.12 × 10−3 AW−1 and detectivity of 0.69 × 109 Jones. This study highlights the potential of CD/P3HT composites for broadband photodetector applications with enhanced photoelectric conversion.

Enhanced Self-Powered Broadband Photodetectors Based on 1-D TiO₂/V₂O₅ Core-Cell Heterojunction

Enhanced Self-Powered Broadband Photodetectors Based on 1-D TiO₂/V₂O₅ Core-Cell Heterojunction

Ultraviolet-Visible-Near-Infrared Broadband Photodetector Enabled by Cs2AgBiBr6: Sn/Conjugated Polymer Heterojunction.

Broadband photodetectors covering ultraviolet (UV) to near-infrared (NIR) wavelengths play an essential role in communications, imaging, and biosensing. Developing a single photodetector with a broadband optical response operating at room temperature can significantly reduce the complexity and cost of receiver systems for multispectral applications. In this work, utilizing the porous structure characteristics of Cs2AgBiBr6:Sn thin films, a self-powered detector with broad spectral response (UV-vis-NIR) was achieved by constructing an effective Cs2AgBiBr6:Sn/PDPP3T heterojunction. This photodetector possesses a broad response spectrum from 350 to 950 nm with an average detection rate exceeding 1011 Jones and maintains excellent photoelectric performance over two months. Sn2+ doping effectively reduces the bandgap of Cs2AgBiBr6, enhancing its near-infrared absorption and optimizing energy level alignment with conjugated polymer (diketopyrrolopyrrole-terthiophene, PDPP3T). More importantly, the porous structure derived from Sn doping significantly improves carrier extraction and transport under a near-infrared light response at the heterojunction interface. Utilizing its broad spectral response characteristics in the UV-vis-NIR range, a novel information transfer and encryption system employing full optical modulation has been realized within a single perovskite photodetector. This work provides a new approach to fabricating lead-free double perovskite broadband photodetectors with potential applications in photonic devices.

Air-stable and UV-NIR broadband photodetectors utilizing graphene and core/shell quantum dots hybrid heterostructure

Photodetectors based on PbSe quantum dots (QDs) are commonly used for light detection in the near-infrared (NIR) region. Nevertheless, the performance of photodetectors based on PbSe QDs is constrained by ineffective carrier transfer and poor photo and thermal stabilities. Herein, a promising strategy that harnesses PbSe/PbS core/shell QDs structures is developed and demonstrated to enhance the long-term stability of photodetectors, further combining with graphene to form hybrid heterojunctions that effectively promote carrier transfer. As a result, the devices exhibit a broad photoresponse to the incident light at range of 365–1250 nm, and also possess a high photosensitivity of 1.5 × 104 A/W and a high detectivity of 4.0 × 1013 Jones. Moreover, the lifetime of graphene-PbSe/PbS core/shell QDs hybrid photodetector was 9 times greater than that of uncoated QDs devices. The enormous boost might be attributed to the passivation and protection provided by the core–shell structure, and graphene’s efficient extraction of charge carriers.

Decipher the Wavelength and Intensity Using Photothermoelectric Detectors.

Broadband photodetectors that can decipher the wavelength (λ) and intensity (I) of an unknown incident light are urgently demanded. Photothermoelectric (PTE) detectors can achieve ultrabroadband photodetection surpassing the bandgap limitation; however, their practical application is severely hampered by the lack of deciphering strategy. In this work, we report a variable elimination method to decipher λ and I of the incident lights based on an integrated Ag2Se film-based PTE detector. Nanostructured Ag2Se films with controlled thickness are synthesized using an ion sputtering of Ag and a room-temperature selenization method and then assembled into a detector. Under identical illumination, Ag2Se films of different thicknesses produce varying output photothermal voltages, influenced by factors including λ. By establishing a direct relationship between the photothermal voltage and the absorption of Ag2Se films of varied thickness, we successfully eliminate variables independent of λ, thus determining λ. Subsequently, I is determined by the calibrated responsivity relationship using obtained λ. Our PTE detector achieves a broadband spectrum from 400 to 950 nm and high accuracy, with deviations as low as ∼2.63 and ∼0.53% for deciphered λ and I, respectively. This method allows for self-powered broadband decipherable photodetection without a complex device architecture or computational assistance, which could boost the research enthusiasm and promote the commercialization of PTE broadband detectors.

2D Gr/WSe2/MoTe2 vertical heterojunction for self-powered photodiode with ultrafast response and high sensitivity

Two-dimensional materials without lattice constraints can be combined into form heterojunctions via van der Waals forces, providing opportunities for the future development of novel high-performance photodetectors. In non-vertical heterojunction devices with long carrier transport channels, SRH recombination due to defect and interface states in the heterojunction and Langevin recombination due to Coulomb interactions induce large amounts of photogenerated carrier recombination, leading to low quantum efficiencies of the heterojunction. At the same time, defect and interface trap states, as well as the long channel of the non-vertical heterojunction device, lead to a slow response speed of the device. In this work, a 2D WSe2/MoTe2 vertical heterojunction photodiode with a transparent graphene top electrode has been designed to simultaneously achieve high sensitivity and fast response speed of photodetectors. Benefiting from the vertical device structure, high-quality interface and low contact resistance, the photogenerated electron-hole pairs can be efficiently separated and transported. The photodiode exhibits remarkable rectification characteristics with a rectification ratio as high as 1.4 × 104, and provides a broadband and self-powered photodetection from the visible to NIR bands (405–1064 nm) with a maximum responsivity of 0.33 A/W at 785 nm. In particular, the photodiode achieves an ultra-fast rise/fall time of 6.49/6.22 μs at 0 V and a further reduction of the response time to 1.68/1.2 μs at a reverse bias of −1 V. This ultra-fast response allows the photodiode to detect switching signals with a cutoff frequency of more than 70 kHz and 200 kHz at 0 V and −1 V, respectively. This work opens up new opportunities for the development of integrated 2D photodetectors with low power consumption, high sensitivity, and high speed.