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Showing papers on "Photodiode published in 2020"


Journal ArticleDOI
TL;DR: Organic photodetectors based on a novel ultranarrow-bandgap nonfullerene acceptor, CO1-4Cl, are presented, showcasing a remarkable responsivity over 0.5 A W-1 in the NIR spectral region (920-960 nm), which is the highest among organic photodiodes.
Abstract: Sensitive detection of near-infrared (NIR) light enables many important applications in both research and industry. Current organic photodetectors suffer from low NIR sensitivity typically due to early absorption cutoff, low responsivity, and/or large dark/noise current under bias. Herein, organic photodetectors based on a novel ultranarrow-bandgap nonfullerene acceptor, CO1-4Cl, are presented, showcasing a remarkable responsivity over 0.5 A W-1 in the NIR spectral region (920-960 nm), which is the highest among organic photodiodes. By effectively delaying the onset of the space charge limited current and suppressing the shunt leakage current, the optimized devices show a large specific detectivity around 1012 Jones for NIR spectral region up to 1010 nm, close to that of a commercial Si photodiode. The presented photodetectors can also be integrated in photoplethysmography for real-time heart-rate monitoring, suggesting its potential for practical applications.

228 citations


Journal ArticleDOI
06 Nov 2020-Science
TL;DR: The performance of optimized organic photodiodes is found to rival that of low-noise silicon photodidaes in all metrics within the visible spectral range, except response time, which is still video-rate compatible.
Abstract: Silicon photodiodes are the foundation of light-detection technology; yet their rigid structure and limited area scaling at low cost hamper their use in several emerging applications. A detailed methodology for the characterization of organic photodiodes based on polymeric bulk heterojunctions reveals the influence that charge-collecting electrodes have on the electronic noise at low frequency. The performance of optimized organic photodiodes is found to rival that of low-noise silicon photodiodes in all metrics within the visible spectral range, except response time, which is still video-rate compatible. Solution-processed organic photodiodes offer several design opportunities exemplified in a biometric monitoring application that uses ring-shaped, large-area, flexible, organic photodiodes with silicon-level performance.

170 citations


Journal ArticleDOI
TL;DR: Direct CPL detection by a photodiode using a helical one-dimensional structure of lead halide perovskites composed of naphthylethylamine-based chiral organic cations is reported, which largely surpasses the direct detecting CPL devices (<4) using chiral plasmonic metamaterials and organic materials.
Abstract: Detection of circularly polarized light (CPL) has a high potential for development of various optical technologies. Conventional photodetectors require optical polarizers on the device to detect polarized light, and this causes substantial losses of sensitivity and resolution in light detection. Here, we report direct CPL detection by a photodiode using a helical one-dimensional (1D) structure of lead halide perovskites composed of naphthylethylamine-based chiral organic cations. The 1D structure with face-sharing (PbI6)4− octahedral chains whose helicity is largely affected by chiral cations shows intense circular dichroism (CD) signals over 3000 mdeg at 395 nm with the highly anisotropy factor (gCD) of 0.04. This high CD enables photocurrent detection with effective discrimination between left-handed and right-handed CPLs. The CPL detector based on this 1D perovskite achieved the highest polarization discrimination ratio of 25.4, which largely surpasses the direct detecting CPL devices (

120 citations



Journal ArticleDOI
TL;DR: In this article, different types of laser source modulation techniques have been used in various applications depending on the objective, as optical systems extract the laws and the best solutions from experiments and simulations, using simulation software with different modulation types so the output signals can be compared.
Abstract: Different types of laser source modulation techniques have been used in various applications depending on the objective. As optical systems extract the laws and the best solutions from experiments and simulations, the present study uses simulation software with different modulation types so the output signals can be compared. The modulators used are Mach-Zehnder, which is an external modulator, and electro-absorption modulator and laser rate equation modulator, which are direct modulators. All these types have an optical link multimode (MM) fiber with a photodiode in the receiver end that can be modeled. The input and output signals are analyzed using different types of modulations.

83 citations


Journal ArticleDOI
TL;DR: This work introduces a general solution for printing wavelength-selective bulk-heterojunction photodetectors through engineering of the ink formulation that effectively decouples the optical response from the viscoelastic ink properties, simplifying process development.
Abstract: Future lightweight, flexible, and wearable electronics will employ visible-light-communication schemes to interact within indoor environments. Organic photodiodes are particularly well suited for such technologies as they enable chemically tailored optoelectronic performance and fabrication by printing techniques on thin and flexible substrates. However, previous methods have failed to address versatile functionality regarding wavelength selectivity without increasing fabrication complexity. This work introduces a general solution for printing wavelength-selective bulk-heterojunction photodetectors through engineering of the ink formulation. Nonfullerene acceptors are incorporated in a transparent polymer donor matrix to narrow and tune the response in the visible range without optical filters or light-management techniques. This approach effectively decouples the optical response from the viscoelastic ink properties, simplifying process development. A thorough morphological and spectroscopic investigation finds excellent charge-carrier dynamics enabling state-of-the-art responsivities >102 mA W-1 and cutoff frequencies >1.5 MHz. Finally, the color selectivity and high performance are demonstrated in a filterless visible-light-communication system capable of demultiplexing intermixed optical signals.

74 citations


Journal ArticleDOI
01 Sep 2020
TL;DR: In this article, an aquatic-vision-inspired camera that consists of a single monocentric lens and a hemispherical silicon nanorod photodiode array is presented.
Abstract: Conventional wide-field-of-view cameras consist of multi-lens optics and flat image sensor arrays, which makes them bulky and heavy As a result, they are poorly suited to advanced mobile applications such as drones and autonomous vehicles In nature, the eyes of aquatic animals consist of a single spherical lens and a highly sensitive hemispherical retina, an approach that could be beneficial in the development of synthetic wide-field-of-view imaging systems Here, we report an aquatic-vision-inspired camera that consists of a single monocentric lens and a hemispherical silicon nanorod photodiode array The imaging system features a wide field of view, miniaturized design, low optical aberration, deep depth of field and simple visual accommodation Furthermore, under vignetting, the photodiode array enables high-quality panoramic imaging due to the enhanced photodetection properties of the silicon nanorod photodiodes By integrating a single monocentric lens with a hemispherical silicon nanorod photodiode array, a wide-field-of-view camera is created that offers low optical aberration, deep depth of field and simple visual accommodation

73 citations


Journal ArticleDOI
TL;DR: In this article, a quantitative relationship between the magnitude of the dark current density under reverse bias (Jd) and the properties of the bulk heterojunction active layer has so far not been established.
Abstract: Minimizing the reverse bias dark current while retaining external quantum efficiency is crucial if the light detection sensitivity of organic photodiodes (OPDs) is to compete with inorganic photodetectors. However, a quantitative relationship between the magnitude of the dark current density under reverse bias (Jd) and the properties of the bulk heterojunction (BHJ) active layer has so far not been established. Here, a systematic analysis of Jd in state-of-the-art BHJ OPDs using five polymers with a range of energy levels and charge transport characteristics is presented. The magnitude and activation energy of Jd are explained using a model that assumes charge injection from the metal contacts into an energetically disordered semiconductor. By relating Jd to material parameters, insights into the origin of Jd are obtained that enable the future selection of successful OPD materials.

69 citations


Journal ArticleDOI
01 Dec 2020-PhotoniX
TL;DR: In this paper, a Si3N4/Si detector with an open-circuit voltage of 0.41 V is fabricated by chemical vapor deposition methods, and exhibits good performance with repeatability.
Abstract: For a practical photodetector, fast switching speed and high on-off ratio are essential, and more importantly, the integration capability of the device finally determines its application level. In this work, the judiciously engineered Si3N4/Si detector with an open-circuit voltage of 0.41 V is fabricated by chemical vapor deposition methods, and exhibits good performance with repeatability. The advanced integration technology of Si3N4 and Si is the foundation for imaging functions in the near future. Compare to the current commercial Si p-i-n photodiodes, the detector cuts off the long-wavelength UV light over 260 nm, realizing the spectrum selectivity without filters or complexed accessories. The stability of this detector is further characterized by cycling response, temperature and light intensity dependence tests. In addition, we also analyze and explain the inherent mechanisms that govern the different operations of two types of Si3N4/Si photodetectors.

69 citations


Journal ArticleDOI
TL;DR: The uni-traveling-carrier photodiode (UTC-PD) is a kind of pin junction photodiodes that selectively uses electrons as active carriers as mentioned in this paper.
Abstract: The uni-traveling-carrier photodiode (UTC-PD) is a kind of pin junction photodiode that selectively uses electrons as active carriers. The diode structure has a relatively thin p-type absorber where electrons are generated as minority carriers, and then they diffuse and/or field-accelerate toward the collector. Since the electrons travel in the depleted collector at a ballistically high velocity, the photoresponse performance of a UTC-PD is superior to that of a conventional pin-PD. In this tutorial, the basics of the current response in a UTC-PD, the electron transport in the p-type absorber, and the performance of a terahertz-wave UTC photomixer, as a representative, are described.

64 citations


Journal ArticleDOI
TL;DR: In this article, the photon-trapping microstructures were introduced into GeSn-based photodetectors for the first time, and achieved high-efficiency photo detection at 2 µm with a responsivity of 0.11 A/W.
Abstract: We introduced photon-trapping microstructures into GeSn-based photodetectors for the first time, and achieved high-efficiency photo detection at 2 µm with a responsivity of 0.11 A/W. The demonstration was realized by a GeSn/Ge multiple-quantum-well (MQW) p-i-n photodiode on a GeOI architecture. Compared with the non-photon-trapping counterparts, the patterning and etching of photon-trapping microstructure can be processed in the same step with mesa structure at no additional cost. A four-fold enhancement of photo response was achieved at 2 µm. Although the incorporation of photo-trapping microstructure degrades the dark current density which increases from 31.5 to 45.2 mA/cm2 at -1 V, it benefits an improved 3-dB bandwidth of 2.7 GHz at bias voltage at -5 V. The optical performance of GeSn/Ge MQW photon-trapping photodetector manifests its great potential as a candidate for efficient 2 µm communication. Additionally, the underlying GeOI platform enables its feasibility of monolithic integration with other photonic components such as waveguide, modulator and (de)multiplexer for optoelectronic integrated circuits (OEICs) operating at 2 µm.

Journal ArticleDOI
TL;DR: In this article, a dual-mode β-Ga2O3 metal-oxide-semiconductor (MOS)-structured photodiode solar-blind detector is introduced, which shows a rectifying ratio of 2 × 103 at ±10 V with a low reverse leakage current of 1.05 pA.
Abstract: Sensitive, high photoresponse and energy-saving detectors are urgently required to monitor solar-blind UV signals. The impressive advantages of Ga2O3 in this field give rise to extensive research and studies. A high-performance dual-mode β-Ga2O3 metal–oxide–semiconductor (MOS)-structured photodiode solar-blind detector is introduced. The device shows a rectifying ratio of 2 × 103 at ±10 V with a low reverse leakage current of 1.05 pA. Under 1.1 μW cm−2 254 nm light illumination, it provides a specific detectivity (D*) of ∼1013 Jones, a high responsivity (R) of 189.89/3.96 A W−1 and a high external quantum efficiency (EQE) of 92 879%/1936% at 10/−10 V, suggesting a high-resolution and sensitive detection in the dual operating (photoconductive/depletion) mode. At zero bias, it exhibits an ultralow dark current of 4.2 pA, an R of 33.48 mA W−1, an EQE of 16.37% and a D* of 1.83 × 1011 Jones, yielding a self-powered operation owing to the enhanced built-in electrical field. Moreover, at ±200 V, the device still avoids breakdown and displays an R of 3930.55 A W−1 and a D* of 1015 Jones, allowing harsh environmental operation. In addition, no obvious degeneration was observed after two months storage. The dual-mode photodiode promises to perform solar-blind detection along with sensitive, stable and self-powered performances.

Journal ArticleDOI
30 Mar 2020-ACS Nano
TL;DR: It is demonstrated that in this specific configuration, the signal to noise ratio for infrared photodetection can be enhanced by two orders of magnitude, and that photovoltaic operation can be achieved.
Abstract: Nanocrystals are promising building blocks for the development of low-cost infrared optoelectronics. Gating a nanocrystal film in a phototransistor geometry is commonly proposed as a strategy to tune the signal-to-noise ratio by carefully controlling the carrier density within the semiconductor. However, the performance improvement has so far been quite marginal. With metallic electrodes, the gate dependence of the photocurrent follows the gate-induced change of the dark current. Graphene presents key advantages: (i) infrared transparency that allows back-side illumination, (ii) vertical electric field transparency, and (iii) carrier selectivity under gate bias. Here, we investigate a configuration of 2D/0D infrared photodetectors taking advantage of a high capacitance ionic glass gate, large-scale graphene electrodes, and a HgTe nanocrystals layer of high carrier mobility. The introduction of graphene electrodes combined with ionic glass enables one to reconfigure selectively the HgTe nanocrystals and the graphene electrodes between electron-doped (n) and hole-doped (p) states. We unveil that this functionality enables the design a 2D/0D p-n junction that expands throughout the device, with a built-in electric field that assists charge dissociation. We demonstrate that, in this specific configuration, the signal-to-noise ratio for infrared photodetection can be enhanced by 2 orders of magnitude, and that photovoltaic operation can be achieved. The detectivity now reaches 109 Jones, whereas the device only absorbs 8% of the incident light. Additionally, the time response of the device is fast (<10 μs), which strongly contrasts with the slow response commonly observed for 2D/0D mixed-dimensional heterostructures, where larger photoconduction gains come at the cost of slower response.

Journal ArticleDOI
TL;DR: The proposed CT states are non-equilibrium mid-gap traps which contribute to photocurrent by a non-linear process of optical release, upconverting them to the CT state which motivates the implementation of a two-diode model often used in emissive inorganic semiconductors.
Abstract: Detailed balance is a cornerstone of our understanding of artificial light-harvesting systems. For next generation organic solar cells, this involves intermolecular charge-transfer (CT) states whose energies set the maximum open circuit voltage VOC. We have directly observed sub-gap states significantly lower in energy than the CT states in the external quantum efficiency spectra of a significant number of organic semiconductor blends. Taking these states into account and using the principle of reciprocity between emission and absorption results in non-physical radiative limits for the VOC. We propose and provide compelling evidence for these states being non-equilibrium mid-gap traps which contribute to photocurrent by a non-linear process of optical release, upconverting them to the CT state. This motivates the implementation of a two-diode model which is often used in emissive inorganic semiconductors. The model accurately describes the dark current, VOC and the long-debated ideality factor in organic solar cells. Additionally, the charge-generating mid-gap traps have important consequences for our current understanding of both solar cells and photodiodes – in the latter case defining a detectivity limit several orders of magnitude lower than previously thought. The inability to accurately measure the charge-generating energy states in organic solar cells makes elucidating the photovoltaic effect in these devices difficult. Here, the authors report charge-generating mid-gap trap states in organic solar cells via ultra-sensitive photovoltaic measurements.

Journal ArticleDOI
TL;DR: A novel van der Waals (vdW) TMDs heterojunction photo-diode composed of black phosphorus (p-BP) and palladium diselenide (n-PdSe2) which establish a high and tunable rectification and photoresponsivity and demonstrates extraordinary values of detectivity and external quantum efficiency.
Abstract: Van der Waals heterostructures composed of transition-metal dichalcogenide (TMD) materials have become a remarkable compact system that could offer an innovative architecture for advanced engineering in high-performance energy-harvesting and optoelectronic devices. Here, we report a novel van der Waals (vdW) TMD heterojunction photodiode composed of black phosphorus (p-BP) and palladium diselenide (n-PdSe2), which establish a high and tunable rectification and photoresponsivity. A high rectification up to ≈7.1 × 105 is achieved, which is successfully tuned by employing the back-gate voltage to the heterostructure devices. Besides, the device significantly shows the high and gate-controlled photoresponsivity of R = 9.6 × 105, 4.53 × 105 and 1.63 × 105 A W-1 under the influence of light of different wavelengths (λ = 532, 1064, and 1310 nm) in visible and near-infrared regions, respectively, because of interlayer optical transition and low Schottky. The device also demonstrates extraordinary values of detectivity (D = 5.8 × 1013 Jones) and external quantum efficiency (EQE ≈ 9.4 × 106), which are an order of magnitude higher than the currently reported values. The effective enhancement of photovoltaic characteristics in visible and infrared regions of this TMD heterostructure-based system has a huge potential in the field of optoelectronics to realize high-performance infrared photodetectors.

Journal ArticleDOI
01 Jan 2020-Small
TL;DR: In this article, a dual-gated (DG) MoS2 phototransistor operating based on the interface coupling effect (ICE) was demonstrated, and the results showed that the ICE plays an important role in the modulation of photoelectric performances.
Abstract: 2D transition metal dichalcogenides (TMDs) based photodetectors have shown great potential for the next generation optoelectronics. However, most of the reported MoS2 photodetectors function under the photogating effect originated from the charge-trap mechanism, which is difficult for quantitative control. Such devices generally suffer from a poor compromise between response speed and responsivity (R) and large dark current. Here, a dual-gated (DG) MoS2 phototransistor operating based on the interface coupling effect (ICE) is demonstrated. By simultaneously applying a negative top-gate voltage (VTG ) and positive back-gate voltage (VBG ) to the MoS2 channel, the photogenerated holes can be effectively trapped in the depleted region under TG. An ultrahigh R of ≈105 A W-1 and detectivity (D*) of ≈1014 Jones are achieved in several devices with different thickness under Pin of 53 µW cm-2 at VTG = -5 V. Moreover, the response time of the DG phototransistor can also be modulated based on the ICE. Based on these systematic measurements of MoS2 DG phototransistors, the results show that the ICE plays an important role in the modulation of photoelectric performances. The results also pave the way for the future optoelectrical application of 2D TMDs materials and prompt for further investigation in the DG structured phototransistors.

Journal ArticleDOI
TL;DR: In this article, a WZO/Si photodiode exhibits current rectifying behaviour (with rectification ratio 155 at 15 V), self-powered photodetection, improved photoresponsivity and detectivity in broad in spectral range 390-1080nm and higher electrical stability in dark and under illumination.

Journal ArticleDOI
TL;DR: In this article, an experimental comparison of the two most established optoelectronic emitters for continuous-wave (cw) terahertz generation: a uni-traveling-carrier photodiode (UTC-PD) and a pin-photodiode(PIN-PD), was carried out.
Abstract: We carried out an experimental comparison study of the two most established optoelectronic emitters for continuous-wave (cw) terahertz generation: a uni-traveling-carrier photodiode (UTC-PD) and a pin-photodiode (PIN-PD). Both diodes are commercially available and feature a similar package (fiber-pigtailed housings with a hyper-hemispherical silicon lens). We measured the terahertz output as a function of optical illumination power and bias voltage from 50 GHz up to 1 THz, using a precisely calibrated terahertz power detector. We found that both emitters were comparable in their spectral power under the operating conditions specified by the manufacturers. While the PIN-PD turned out to be more robust against varying operating parameters, the UTC-PD showed no saturation of the emitted terahertz power even for 50 mW optical input power. In addition, we compared the terahertz transmission and infrared (IR) blocking ratio of four different filter materials. These filters are a prerequisite for correct measurements of the absolute terahertz power with thermal detectors.

Journal ArticleDOI
TL;DR: In this paper, the electrical characteristics of spin-coated PCBM:ZnO interlayered Al/PCBM: ZnO/Si diode are investigated under the aim of photodiode application.

Journal ArticleDOI
TL;DR: The thickness-modulated spontaneously formed lateral WSe2-WSe2 homojunction photodiodes are reported, which have unique band structure with a unilateral depletion region and can achieve a high detectivity and fast photoresponse speed under zero external voltage.
Abstract: Lateral homojunctions made of two-dimensional (2D) layered materials are promising for optoelectronic and electronic applications. Here, we report the lateral WSe2-WSe2 homojunction photodiodes formed spontaneously by thickness modulation in which there are unique band structures of a unilateral depletion region. The electrically tunable junctions can be switched from n-n to p-p diodes, and the corresponding rectification ratio increases from about 1 to 1.2 × 104. In addition, an obvious photovoltaic behavior is observed at zero gate voltage, which exhibits a large open voltage of 0.49 V and a short-circuit current of 0.125 nA under visible light irradiation. In addition, due to the unilateral depletion region, the diode can achieve a high detectivity of 4.4 × 1010 Jones and a fast photoresponse speed of 0.18 ms at Vg = 0 and Vds = 0. The studies not only demonstrated the great potential of the lateral homojunction photodiodes for a self-power photodetector but also allowed for the development of other functional devices, such as a nonvolatile programmable diode for logic rectifiers.

Journal ArticleDOI
TL;DR: A device with a certified external quantum efficiency above 130% in UV range without external amplification is demonstrated and it is shown that the high efficiency is based on effective utilization of multiple carrier generation by impact ionization taking place in the nanostructures.
Abstract: At present, ultraviolet sensors are utilized in numerous fields ranging from various spectroscopy applications via biotechnical innovations to industrial process control. Despite this, the performance of current UV sensors is surprisingly poor. Here, we break the theoretical one-photon--one-electron barrier and demonstrate a device with a certified external quantum efficiency above 130% in UV range without external amplification. The record high performance is obtained using a nanostructured silicon photodiode with self-induced junction. We show that the high efficiency is based on effective utilization of multiple carrier generation by impact ionization taking place in the nanostructures. While the results can readily have a significant impact on the UV-sensor industry, the underlying technological concept can be applied to other semiconductor materials, thereby extending above unity response to longer wavelengths and offering new perspectives for improving efficiencies beyond the Shockley-Queisser limit.

Journal ArticleDOI
TL;DR: A nanomechanical sensor with 80nm bandwidth, displacement imprecision of 45 fm/Hz 1/2 as well as a dynamic range greater than 30 nm with integrated photodetectors is presented.
Abstract: Optical read-out of motion is widely used in sensing applications. Recent developments in micro- and nano-optomechanical systems have given rise to on-chip mechanical sensing platforms, potentially leading to compact and integrated optical motion sensors. However, these systems typically exploit narrow spectral resonances and therefore require tuneable lasers with narrow linewidth and low spectral noise, which makes the integration of the read-out extremely challenging. Here, we report a step towards the practical application of nanomechanical sensors, by presenting a sensor with ultrawide (∼80 nm) optical bandwidth. It is based on a nanomechanical, three-dimensional directional coupler with integrated dual-channel waveguide photodiodes, and displays small displacement imprecision of only 45 fm/Hz1/2 as well as large dynamic range (>30 nm). The broad optical bandwidth releases the need for a tuneable laser and the on-chip photocurrent read-out replaces the external detector, opening the way to fully-integrated nanomechanical sensors.

Journal ArticleDOI
TL;DR: The HgTe colloidal quantum dots photodiodes achieved external quantum efficiencies above 50% and specific detectivities of 1'×'1011 at 2.2'μm at room temperature with a microsecond response time as mentioned in this paper.
Abstract: HgTe colloidal quantum dots are investigated as the active material in photodiodes for extended short-wave infrared up to 2.6 μm. The HgTe colloidal quantum dots photodiodes achieve external quantum efficiencies above 50% and specific detectivities of 1 × 1011 at 2.2 μm at room temperature with a microsecond response time and compete with commercial extended InGaAs photodiodes.

Journal ArticleDOI
TL;DR: The geometry of cavity-coupled palladium nanostructures as well as the optical system concept are systematically investigated, which enables the robust detection of hydrogen at concentrations down to 100 ppm and can be applied to any type of plasmonic sensor.
Abstract: Palladium nanoparticles have proven to be exceptionally suitable materials for the optical detection of hydrogen gas due to the dielectric function that changes with the hydrogen concentration. The development of a reliable, low-cost, and widely applicable hydrogen detector requires a simple optical readout mechanism and an optimization of the lowest detectable hydrogen concentration. The so-called "perfect absorber"-type structures, consisting of a layer of plasmonic palladium nanoantennas suspended above a metallic mirror layer, are a promising approach to realizing such sensors. The absorption of hydrogen by palladium leads to a shift of the plasmon resonance and, thus, to a change in the far-field reflectance spectrum. The spectral change can be analyzed in detail using spectroscopic measurements, while the reflectance change at a specific wavelength can be detected with a simple photometric system of a photodiode and a monochromatic light source. Here, we systematically investigate the geometry of cavity-coupled palladium nanostructures as well as the optical system concept, which enables us to formulate a set of design rules for optimizing the hydrogen sensitivity. Employing these principles, we demonstrate the robust detection of hydrogen at concentrations down to 100 ppm. Our results are not limited to hydrogen sensing but can be applied to any type of plasmonic sensor.

Journal ArticleDOI
TL;DR: A highly sensitive and flexible photoelectric detector is the key to accurate, real-time, and noninvasive monitoring of health signals, such as heart rate, for mobile health care.
Abstract: Accurate, real-time, and noninvasive monitoring of health signals, such as heart rate, is indispensable for mobile health care. A highly sensitive and flexible photoelectric detector is the key com...

Journal ArticleDOI
29 Apr 2020
TL;DR: Wu et al. as mentioned in this paper presented experimental and modeling studies on the noise current in exemplar organic bulk heterojunction photodiodes, with 10 donor-acceptor combinations spanning wavelength between 800 and 1600 nm.
Abstract: Author(s): Wu, Zhenghui; Li, Ning; Eedugurala, Naresh; Azoulay, Jason D; Leem, Dong-Seok; Ng, Tse Nga | Abstract: AbstractTo achieve high detectivity in infrared detectors, it is critical to reduce the device noise. However, for non-crystalline semiconductors, an essential framework is missing to understand and predict the effects of disorder on the dark current. This report presents experimental and modeling studies on the noise current in exemplar organic bulk heterojunction photodiodes, with 10 donor–acceptor combinations spanning wavelength between 800 and 1600 nm. A significant reduction of the noise and higher detectivity were found in devices using non-fullerene acceptors (NFAs) in comparison to those using fullerene derivatives. The low noise in NFA blends was attributed to a sharp drop off in the distribution of bandtail states, as revealed by variable-temperature density-of-states measurements. Taking disorder into account, we developed a general physical model to explain the dependence of thermal noise on the effective bandgap and bandtail spread. The model provides theoretical targets for the maximum detectivity that can be obtained at different detection wavelengths in inherently disordered infrared photodiodes.


Journal ArticleDOI
TL;DR: In this article, a high performance p-GaN/n-ZnMgO heterojunction photodiode was demonstrated and investigated, which showed a clear rectifying I-V characteristic with a turn-on voltage of 2.5 V.
Abstract: A high performance p-GaN/n-ZnMgO heterojunction photodiode was demonstrated and investigated. A high quality p-GaN film was grown on GaN/sapphire templates by plasma-assisted molecular beam epitaxy and subsequently an n-ZnMgO layer was deposited on p-GaN by a metal organic chemical vapor deposition technique. The p-GaN/n-ZnMgO heterojunction photodetector shows a clear rectifying I–V characteristic with a turn-on voltage of 2.5 V. At zero-bias voltage, the device shows a high peak responsivity of 196 mA W−1 at 362 nm. The 10–90% rise time and 90–10% decay time of the device can be as short as 1.7 ms and 3.3 ms, respectively. The excellent crystal quality and electrical properties of p-GaN play an important role in the high performance of the photodiode. This work provides a feasible way for the development of high-performance heterojunction self-powered UV detectors.

Journal ArticleDOI
Yu Song1, Gang Yu1, Boming Xie1, Kai Zhang1, Fei Huang1 
TL;DR: In this paper, a broadband organic photodiodes (OPDs) with performance comparable to that of crystalline silicon-based commercial devices was developed with a strategy of combining an NIR absorbing non-fullerene acceptor and a thick junction, with a suppressed dark current density of 0.35 nA/cm2, an enhanced spectral response covering 300-1000 nm, and external quantum efficiency over 60% el/ph.
Abstract: Photodetection in the visible and near-infrared (NIR) spectral regions offers a wide range of applications, such as image arrays of high pixel density and artificial intelligence. In this work, broadband organic photodiodes (OPDs) are developed with performance comparable to that of crystalline silicon-based commercial devices. Through the strategy of combining an NIR-absorbing non-fullerene acceptor and a thick junction, the resulting devices show significantly improved performance parameters, with a suppressed dark current density of 0.35 nA/cm2, an enhanced spectral response covering 300–1000 nm, and external quantum efficiency over 60% el/ph. Owing to the low dark current noise and high responsivity to NIR wavelengths, an unexpectedly high specific detectivity of 5.1 × 1013 Jones at 930 nm is obtained together with a linear dynamic range of 157 dB and a −3 dB cutoff frequency of 4.5 kHz. These results reveal that the NIR OPD has great potential for 2D and 3D imaging applications with a high frame rate and multiple band selection.