A parylene/graphene UV photodetector with ultrahigh responsivity and long term stability.

Long term stability, high responsivity, and fast response speed are essential for the commercialization of graphene photodetectors (GPDs). In this work, a parylene/graphene UV photodetector with long term stability, ultrahigh responsivity and fast response speed, is demonstrated. Parylene as a stable physical and chemical insulating layer reduces the environmental sensitivity of graphene, and enhances the performances of GPDs. In addition, utilizing bilayer electrodes reduces the buckling and damage of graphene after transferring. The parylene/graphene UV photodetector exhibits an ultrahigh responsivity of 5.82 × 105AW-1under 325 nm light irradiation at 1 V bias. Additionally, it shows a fast response speed with a rise time of 80µs and a fall time of 17µs, and a long term stability at 405 nm wavelength which is absent in the device without parylene. The parylene/graphene UV photodetector possesses superior performances. This paves the way for the commercial application of the high-performance graphene hybrid photodetectors, and provides a practical method for maintaining the long term stability of two dimensional (2D) materials.

High responsivity photodetector based on MEH-PPV/CsPbBr3heterojunction.

Perovskite quantum dots (QDs) and organic materials have great research potential in the field of optoelectronic devices. In this paper, MEH-PPV/CsPbBr3heterojunction photodetectors (PDs) are prepared by spin coating method based on the good photoelectric properties of CsPbBr3perovskite QDs and MEH-PPV. The MEH-PPV/CsPbBr3heterojunction improves the energy level arrangement, and CsPbBr3QDs can passivate the surface defects of MEH-PPV films to achieve effective charge separation and transfer, thus inhibiting the dark current and improving the photoelectric performance of the device. Under 532 nm laser irradiation, the responsivity (R) of MEH-PPV/CsPbBr3heterojunction PD is 11.98 A W-1, the specific detectivity (D*) is 6.98 × 1011Jones, and the response time is 15/16 ms. This work provides experience for the study of perovskite QDs and organic materials heterojunction optoelectronic devices.

Sol-Gel Synthesized Amorphous (InxGa1-x)2O3 for UV Photodetection with High Responsivity.

ß-Ga2O3 photodetectors have the advantages of low dark current and strong radiation resistance in UV detection. However, the limited photocurrent has restricted their applications. Herein, MSM UV photodetectors based on (InxGa1-x)2O3 (x = 0, 0.1, 0.2, 0.3) by a sol-gel method were fabricated and studied. The doping of indium ions in Ga2O3 leads to lattice distortion and promotes the formation of oxygen vacancies. The oxygen vacancies in (InxGa1-x)2O3 can be modulated by various proportions of indium, and the increased oxygen vacancies contribute to the enhancement of electron concentration. The results show that the amorphous In0.4Ga1.6O3 photodetector exhibited improved performances, including a high light-to-dark current ratio (2.8 × 103) and high responsivity (739.2 A/W). This work provides a promising semiconductor material In0.4Ga1.6O3 for high-performance MSM UV photodetectors.

Achieving High Responsivity and Detectivity in a Quantum-Dot-in-Perovskite Photodetector.

This work reports on quantum dots (QDs) in perovskite photodetectors showing high optoelectronic performance via quantum-dot-assisted charge transmission. The self-powered broad-band photodetector constructed with SnS QDs in FAPb0.5Sn0.5I3 perovskite can capture incoming optical signals directly at zero bias. The QDs-in-perovskite photodetector exhibits a high sensitivity in the wavelength range from 300 to 1000 nm. Its responsivity at 850 nm reaches 521.7 mA W-1, and a high specific detectivity of 2.57 × 1012 jones can be achieved, which is well beyond the level of previous self-powered broad-band photodetectors. The capability of quantum-dot-in-perovskite photodetectors as data receivers has been further demonstrated in a visible-light communication application.

Highly Responsive and Self-Powered Photodetector Based on PtSe2/MoS2 Heterostructure.

In recent years, 2D materials and their heterostructures have started to offer an ideal platform for high-performance photodetection devices. In this work, a highly responsive, self-powered photodetector based on PtSe2/MoS2 van der Waals heterostructure is demonstrated. The device achieves a noteworthy wide band spectral response from visible (405 nm) range to the near infrared region (980 nm). The remarkable photoresponsivity and external quantum efficiency up to 4.52 A/W, and 1880% are achieved, respectively, at 405 nm illumination with fast response time of 20 ms. In addition, the photodetector exhibits a decent photoresponsivity of 33.4 mA/W at zero bias, revealing the photodetector works well in the self-driven mode. Our work suggests that a PtSe2/MoS2 heterostructure could be a potential candidate for the high-performance photodetection applications.

CMOS-Compatible Tellurium/Silicon Ultra-Fast Near-Infrared Photodetector.

High-quality photodetectors are always the main way to obtain external information, especially near-infrared sensors play an important role in remote sensing communication. However, due to the limitation of Silicon (Si) wide bandgap and the incompatibility of most near infrared photoelectric materials with traditional integrated circuits, the development of high performance and wide detection spectrum near infrared detectors suitable for miniaturization and integration is still facing many obstacles. Herein, the monolithic integration of large area tellurium optoelectronic functional units is realized by magnetron sputtering technology. Taking advantage of the type II heterojunction constructed by tellurium (Te) and silicon (Si), the photogenerated carriers are effectively separated, which prolongs the carrier lifetime and improves the photoresponse by several orders of magnitude. The tellurium/silicon (Te/Si) heterojunction photodetector demonstrates excellent detectivity and ultra-fast turn-on time. Importantly, an imaging array (20 × 20 pixels) based on the Te/Si heterojunction is demonstrated and high-contrast photoelectric imaging is realized. Because of the high contrast obtained by the Te/Si array, in comparison with the Si arrays, it significantly improve the efficiency and accuracy of the subsequent processing tasks when the electronic pictures are applied to artificial neural network (ANN) to simulate the artificial vision system.

Manipulating Nanowire Structures for an Enhanced Broad-Band Flexible Photothermoelectric Photodetector.

The photothermoelectric effect, directly converting light energy into electrical energy, shows promising prospects in self-powered broad-band optical detection, which can extend to various applications, such as sensing, optoelectronic communications, and wide-temperature-range measurements. However, the low photosensitivity, narrow-band response, and rapid performance degeneration under continuous illumination restrict its broad application. Herein, we propose a simple bottom-up strategy to manipulate nanowires (NWs) into a well-defined multilayer Te-Ag2Te-Ag NW film, resulting in a high-performance photothermoelectric photodetector with a broad-band responsivity (4.1 V/W), large detectivity (944 MHz1/2 W-1), and fast response speed (0.4-0.7 s from 365 to 1200 nm). In addition, the ultrathin structure endows this device with slow and weak transverse heat conduction, enabling a stable voltage without an obvious degeneration over 1500 s. The highly anisotropic arrangement of NWs gives this device a prominent polarization sensitivity. Prospectively, this hierarchically designed nanowire film provides a promising pathway toward engineering photodetectors with high performance.

Upconversion under Photon Trapping in ZnO/BN Nanoarray: An Ultrahigh Responsivity Solar-Blind Photodetecting Paper.

Solar-blind photodetectors (PDs) are widely applicable in special, military, medical, environmental, and commercial fields. However, high performance and flexible PD for deep ultraviolet (UV) range is still a challenge. Here, it is demonstrated that an upconversion of photon absorption beyond the energy bandgap is achieved in the ZnO nanoarray/h-BN heterostructure, which enables the ultrahigh responsivity of a solar-blind photodetecting paper. The direct growth of ultralong ZnO nanoarray on polycrystalline copper paper induced by h-BN 2D interlayer is obtained. Meanwhile, strong photon trapping takes place within the ZnO nanoarray forest through the cyclic state transition of surface oxygen ions, resulting in an extremely high absorption efficiency (> 99.5%). A flexible photodetecting paper is fabricated for switchable detections between near UV and deep UV signals by critical external bias. The device shows robust reliability, ultrahigh responsivity up to 700 A W-1 @ 265-276 nm, and high photoconductive gain of ≈2 × 103 . A negative differential resistance effect is revealed for driving the rapid transfer of up-converted electrons between adjacent energy valleys (Γ to A) above the critical bias (3.9 V). The discovered rationale and device structure are expected to bring high-efficiency deep UV detecting and future wearable applications.

Substantially Improving Device Performance of All-Inorganic Perovskite-Based Phototransistors via Indium Tin Oxide Nanowire Incorporation.

All-inorganic halide perovskites (IHPs) have attracted enormous attention due to their intrinsically high optical absorption coefficient and superior ambient stabilities. However, the photosensitivity of IHP-based photodetectors is still restricted by their poor conductivities. Here, a facile design of hybrid phototransistors based on the CsPbBr3 thin film and indium tin oxide (ITO) nanowires (NWs) integrated into a InGaZnO channel in order to achieve both high photoresponsivity and fast response is reported. The metallic ITO NWs are employed as electron pumps and expressways to efficiently extract photocarriers from CsPbBr3 and inject electrons into InGaZnO. The obtained device exhibits the outstanding responsivity of 4.9 × 106 A W-1 , which is about 100-fold better than the previous best results of CsPbBr3 -based photodetectors, together with the fast response (0.45/0.55 s), long-term stability (200 h in ambient), and excellent mechanical flexibility. By operating the phototransistor in the depletion regime, an ultrahigh specific detectivity up to 7.6 × 1013 Jones is achieved. More importantly, the optimized spin-coating manufacturing process is highly beneficial for achieving uniform InGaZnO-ITO/perovskite hybrid films for high-performance flexible detector arrays. All these results can not only indicate the potential of these hybrid phototransistors but also provide a valuable insight into the design of hybrid material systems for high-performance photodetection.

Ultra-Broadband Flexible Photodetector Based on Topological Crystalline Insulator SnTe with High Responsivity.

Topological crystalline insulators (TCIs) are predicted to be a promising candidate material for ultra-broadband photodetectors ranging from ultraviolet (UV) to terahertz (THz) due to its gapless surface state and narrow bulk bandgap. However, the low responsivity of TCIs-based photodetectors limits their further applications. In this regard, a high-performance photodetector based on SnTe, a recently developed TCI, working in a broadband wavelength range from deep UV to mid-IR with high responsivity is reported. By taking advantage of the strong light absorption and small bandgap of SnTe, photodetectors based on the as-grown SnTe crystalline nanoflakes as well as specific short channel length achieve a high responsivity (71.11 A W-1 at 254 nm, 49.03 A W-1 at 635 nm, 10.91 A W-1 at 1550 nm, and 4.17 A W-1 at 4650 nm) and an ultra-broad spectral response (254-4650 nm) simultaneously. Moreover, for the first time, a durable flexible SnTe photodetector fabricated directly on a polyethylene terephthalate film is demonstrated. These results prove the great potential of TCIs as a promising material for integrated and flexible optoelectronic devices.

2D Printed Plasmonic Nanoparticle Array Incorporated Formamidinium-Based High-Performance Self-Biased Perovskite Photodetector.

Utilizing noble metal nanoparticles through novel technologies is a promising avenue for enhancing the performance of organic/inorganic photodetectors. This study investigates the performance enhancement of Formamidinium-based perovskite (Pe) photodetectors (PDs) through the incorporation of plasmonic silver nanoparticles (Ag NPs) arrays using a 2D printing technique. The incorporation of plasmonic Ag NPs leads to a major improvement in the performance of the planar PD device, which is attributed to increased light absorption, hot electron generation, and more efficient charge extraction and transport. The unique aspect of this study lies in the method of incorporating plasmonic NPs using a two-dimensional printing technology. This approach offers several advantages over traditional methods, including lower cost, nonvacuum operation, and compatibility with room temperature fabrication. The printed plasmon-enhanced optimized perovskite PD exhibits remarkable performance metrics, including a peak responsivity of 1.03 A/W at 5 V external bias, which is significantly high compared to the reported devices. Moreover, the PD demonstrates exceptional detectivity with a peak value of 3.7 × 1012 Jones at 5 V, highlighting its capability to detect ultralow light signals with high precision. The device can be reversibly switched between low and high conductance states, yielding a stable and repeatable Ilight/Idark ratio of 1.06 × 104. In addition, the integration of plasmonic nanoparticles imparts remarkable photovoltaic characteristics to the perovskite photodetector, enabling it to function as a self-biased device. The hybrid device demonstrates a peak responsivity of 15 mA/W, a high detectivity of 2.15 × 1011 Jones, and a significant on-off ratio of 2.23 × 103, all achieved at zero external bias. Overall, this study presents a significant advancement in the field of plasmon-enhanced Pe photodetection technology. By utilizing the benefits of printing technology to incorporate NPs, we have developed a high-performance PD that combines cost-effectiveness with exceptional performance. Thus, we believe that this study will pave the way for the development of a low-cost, high-performance plasmon-enhanced Pe-based PD.

Printed MoSe2/GaAs Photodetector Enabling Ultrafast and Broadband Photodetection up to 1.5 µm.

The development of high-performance and low-cost photodetectors (PDs) capable of detecting a broad range of wavelengths, from ultraviolet (UV) to near-infrared (NIR), is crucial for applications in sensing, imaging, and communication systems. This work presents a novel approach for printing a broadband PD based on a heterostructure of two-dimensional (2D) molybdenum diselenide (MoSe2) and gallium arsenide (GaAs). The fabrication process involves a precise technique to print MoSe2 nanoflower (NF) ink onto a prepatterned GaAs substrate. The resulting heterostructure exhibits unique properties, leveraging the exceptional electronic and optical characteristics of both GaAs and 2D MoSe2. The fabricated PD achieves an astounding on-off ratio of ∼105 at 5 V bias while demonstrating an exceptional on-off ratio of ∼104 at 0 V. The depletion region between GaAs and MoSe2 facilitates efficient charge generation and separation and collection of photogenerated carriers. This significantly improves the performance of the PD, resulting in a notably high responsivity across the spectrum. The peak responsivity of the device is 5.25 A/W at 5 V bias under 808 nm laser excitation, which is more than an order of magnitude higher than that of any commercial NIR PDs. Furthermore, the device demonstrates an exceptional responsivity of 0.36 A/W under an external bias of 0 V. The printing technology used here offers several advantages including simplicity, scalability, and compatibility with large-scale production. Additionally, it enables precise control over the placement and integration of the MoSe2 NF onto the GaAs substrate, ensuring uniformity and reliability in device performance. The exceptional responsivity across a broad spectral range (360-1550 nm) and the success of the printing technique make our MoSe2/GaAs heterostructure PD promising for future low-cost and efficient optoelectronic devices.

p-Type Schottky Contacts for Graphene Adjustable-Barrier Phototransistors.

The graphene adjustable-barriers phototransistor is an attractive novel device for potential high speed and high responsivity dual-band photodetection. In this device, graphene is embedded between the semiconductors silicon and germanium. Both n-type and p-type Schottky contacts between graphene and the semiconductors are required for this device. While n-type Schottky contacts are widely investigated, reports about p-type Schottky contacts between graphene and the two involved semiconductors are scarce. In this study, we demonstrate a p-type Schottky contact between graphene and p-germanium. A clear rectification with on-off ratios of close to 103 (±5 V) and a distinct photoresponse at telecommunication wavelengths in the infrared are achieved. Further, p-type silicon is transferred to or deposited on graphene, and we also observe rectification and photoresponse in the visible range for some of these p-type Schottky junctions. These results are an important step toward the realization of functional graphene adjustable-barrier phototransistors.

Bolometric IR photoresponse based on a 3D micro-nano integrated CNT architecture.

A new 3D micro-nano integrated M-shaped carbon nanotube (CNT) architecture was designed and fabricated. It is based on vertically aligned carbon nanotube arrays composed of low-density, mainly double-walled CNTs with simple lateral external contacts to the surroundings. Standard optical lithography techniques were used to locally tailor the width of the vertical block structure. The complete sensor system, based on a broadband blackbody absorber region and a high-resistance thermistor region, can be fabricated in a single chemical vapor deposition process step. The thermistor resistance is mainly determined by the high junction resistances of the adjacent aligned CNTs. This configuration also provides low lateral thermal conductivity and a high temperature coefficient of resistance (TCR). These properties are advantageous for new bolometric sensors with high voltage responsivity and broadband absorption from the infrared (IR) to the terahertz spectrum. Preliminary performance evaluations have shown current and voltage responsivities of 2 mA/W and 30 V/W, respectively, in response to IR (980 nm) absorption for a 20 × 20 µm2 device. The device exhibits an exceptionally fast response time of ≈0.15 ms, coupled with a TCR of -0.91 %/K. These attributes underscore its high operating speed and responsivity, respectively. In particular, the device maintains excellent thermal stability and reliable operation at elevated temperatures in excess of 200 °C, extending its potential utility in challenging environmental conditions. This design allows for further device miniaturization using optical lithography techniques. Its unique properties for mass production through large-scale integration techniques make it important for real-time broadband imaging systems.

Negative Photoconductivity of Fe3GeTe2 Crystal with Native Heterostructure for Ultraviolet to Terahertz Ultra-Broadband Photodetection.

Gaining insight into the photoelectric behavior of ferromagnetic materials is significant for comprehensively grasping their intrinsic properties and broadening future application fields. Here, through a specially designed Fe3GeTe2/O-Fe3GeTe2 heterostructure, first, the broad-spectrum negative photoconductivity phenomenon of ferromagnetic nodal line semimetal Fe3GeTe2 is reported that covers UV-vis-infrared-terahertz bands (355 nm to 3000 µm), promising to compensate for the inadequacies of traditional optoelectronic devices. The significant suppression of photoexcitation conductivity is revealed to arise from the semimetal/oxidation (sMO) interface-assisted dual-response mechanism, in which the electron excitation origins from the semiconductor photoconductivity effect in high-energy photon region, and semimetal topological band-transition in low-energy photon region. High responsivities ranging from 103 to 100 mA W-1 are acquired within ultraviolet-terahertz bands under ±0.1 V bias voltage at room temperature. Notably, the responsivity of 2.572 A W-1 at 3000 µm (0.1 THz) and the low noise equivalent power of 26 pW Hz-1/2 surpass most state-of-the-art mainstream terahertz detectors. This research provides a new perspective for revealing the photoelectric conversion properties of Fe3GeTe2 crystal and paves the way for the development of spin-optoelectronic devices.

A Broadband Photodetector Based on PbS Quantum Dots and Graphene with High Responsivity and Detectivity.

A high-efficiency photodetector consisting of colloidal PbS quantum dots (QDs) and single-layer graphene was prepared in this research. In the early stage, PbS QDs were synthesized and characterized, and the results showed that the product conformed with the characteristics of high-quality PbS QDs. Afterwards, the photodetector was derived through steps, including the photolithography and etching of indium tin oxide (ITO) electrodes and the graphene active region, as well as the spin coating and ligand substitution of the PbS QDs. After application testing, the photodetector, which was prepared in this research, exhibited outstanding properties. Under visible and near-infrared light, the highest responsivities were up to 202 A/W and 183 mA/W, respectively, and the highest detectivities were up to 2.24 × 1011 Jones and 2.47 × 108 Jones, respectively, with light densities of 0.56 mW/cm2 and 1.22 W/cm2, respectively. In addition to these results, the response of the device and the rise and fall times for the on/off illumination cycles showed its superior performance, and the fastest response times were approximately 0.03 s and 1.0 s for the rise and fall times, respectively. All the results illustrated that the photodetector based on PbS and graphene, which was prepared in this research, possesses the potential to be applied in reality.

High-Responsivity and Broadband MoS2 Photodetector Using Interfacial Engineering.

Combining MoS2 with mature silicon technology is an effective method for preparing high-performance photodetectors. However, the previously studied MoS2/silicon-based heterojunction photodetectors cannot simultaneously demonstrate high responsivity, a fast response time, and broad spectral detection. We constructed a broad spectral n-type MoS2/p-type silicon-based heterojunction photodetector. The SiO2 dielectric layer on the silicon substrate was pretreated with soft plasma to change its thickness and surface state. The pretreated SiO2 dielectric layer and the silicon substrate constitute a multilayer heterostructure with a high carrier concentration and responsiveness. Taking silicon-based and n-type MoS2 heterojunction photodetectors as examples, its responsivity can reach 4.05 × 104 A W1- at 637 nm wavelength with a power density of 2 µW mm-2, and the detectable spectral range is measured from 447 to 1600 nm. This pretreated substrate was proven applicable to other n-type TMDCs, such as MoTe2, ReS2, etc., with certain versatility.

Highly Efficient Van Der Waals Heterojunction on Graphdiyne toward the High-Performance Photodetector.

Graphdiyne (GDY), a new 2D material, has recently proven excellent performance in photodetector applications due to its direct bandgap and high mobility. Different from the zero-gap of graphene, these preeminent properties made GDY emerge as a rising star for solving the bottleneck of graphene-based inefficient heterojunction. Herein, a highly effective graphdiyne/molybdenum (GDY/MoS2 ) type-II heterojunction in a charge separation is reported toward a high-performance photodetector. Characterized by robust electron repulsion of alkyne-rich skeleton, the GDY based junction facilitates the effective electron-hole pairs separation and transfer. This results in significant suppression of Auger recombination up to six times at the GDY/MoS2 interface compared with the pristine materials owing to an ultrafast hot hole transfer from MoS2 to GDY. GDY/MoS2 device demonstrates notable photovoltaic behavior with a short-circuit current of -1.3 × 10-5 A and a large open-circuit voltage of 0.23 V under visible irradiation. As a positive-charge-attracting magnet, under illumination, alkyne-rich framework induces positive photogating effect on the neighboring MoS2 , further enhancing photocurrent. Consequently, the device exhibits broadband detection (453-1064 nm) with a maximum responsivity of 78.5 A W-1 and a high speed of 50 µs. Results open up a new promising strategy using GDY toward effective junction for future optoelectronic applications.

Organic Photodiodes with Thermally Reliable Dark Current and Excellent Detectivity Enabled by Low Donor Concentration.

Reducing the dark current (Jd) under reverse bias while maintaining a high external quantum efficiency (EQE) is essential for the practical application of organic photodiodes (OPDs). However, the high Jd of OPDs is generally difficult to reduce because its origin in organic photodiodes is still not well understood and is strongly temperature dependent. To address the issues related to high Jd in typical OPDs, we investigate fullerene-based OPDs with various donor concentrations. It is surprising that OPDs with a low donor concentration in the active layer can achieve a very low Jd of 1.68 × 10-7 mA cm-2 at a reverse bias of -2 V, which is almost temperature-independent owing to the low polymer content. More importantly, the fullerene-based OPDs with a low donor concentration of 5 wt % can still achieve an external quantum efficiency (EQE) as high as 40%, resulting in a promisingly high detectivity of above 1013 Jones at 300-800 nm compared to the OPDs with a standard donor/acceptor ratio. The presented optimized OPD device can also be used for real-time heart rate detection, indicating its potential for practical photon-sensing applications.

Deep-Ultraviolet Transparent Electrode Design for High-Performance and Self-Powered Perovskite Photodetector.

In this study, a highly crystalline and transparent indium-tin-oxide (ITO) thin film was prepared on a quartz substrate via RF sputtering to fabricate an efficient bottom-to-top illuminated electrode for an ultraviolet C (UVC) photodetector. Accordingly, the 26.6 nm thick ITO thin film, which was deposited using the sputtering method followed by post-annealing treatment, exhibited good transparency to deep-UV spectra (67% at a wavelength of 254 nm), along with high electrical conductivity (11.3 S/cm). Under 254 nm UVC illumination, the lead-halide-perovskite-based photodetector developed on the prepared ITO electrode in a vertical structure exhibited an excellent on/off ratio of 1.05 × 104, a superb responsivity of 250.98 mA/W, and a high specific detectivity of 4.71 × 1012 Jones without external energy consumption. This study indicates that post-annealed ITO ultrathin films can be used as electrodes that satisfy both the electrical conductivity and deep-UV transparency requirements for high-performance bottom-illuminated optoelectronic devices, particularly for use in UVC photodetectors.