Showing papers on "Responsivity published in 2022"

In Situ Fabrication of PdSe2/GaN Schottky Junction for Polarization-Sensitive Ultraviolet Photodetection with High Dichroic Ratio.

Abstract: Polarization-sensitive ultraviolet (UV) photodetection is of great technological importance for both civilian and military applications. Two-dimensional (2D) group-10 transition-metal dichalcogenides (TMDs), especially palladium diselenide (PdSe2), are promising candidates for polarized photodetection due to their low-symmetric crystal structure. However, the lack of an efficient heterostructure severely restricts their applications in UV-polarized photodetection. Here, we develop a PdSe2/GaN Schottky junction by in situ van der Waals growth for highly polarization-sensitive UV photodetection. Owing to the high-quality junction, the device exhibits an appealing UV detection performance in terms of a large responsivity of 249.9 mA/W, a high specific detectivity, and a fast response speed. More importantly, thanks to the puckered structure of the PdSe2 layer, the device is highly sensitive to polarized UV light with a large dichroic ratio up to 4.5, which is among the highest for 2D TMD material-based UV polarization-sensitive photodetectors. These findings further enable the demonstration of the outstanding polarized UV imaging capability of the Schottky junction, as well as its utility as an optical receiver for secure UV optical communication. Our work offers a strategy to fabricate the PdSe2-based heterostructure for high-performance polarization-sensitive UV photodetection.

An All‐Organic Self‐Powered Photodetector with Ultraflexible Dual‐Polarity Output for Biosignal Detection

Abstract: Endowing photodetectors with mechanically flexibility and actual functionality are current research issues in developing optoelectronic devices. However, rigid metal‐based or metal‐oxide‐based electrodes remain a block to the realization of ultraflexible electronics. Thus, an ultraflexible all‐organic photodetector (all‐OPD) is designed by innovatively introducing symmetrical organic electrodes PH1000/PH1000 to substitute the widely applied indium‐doped tin oxide (ITO)/Ag electrodes. Specifically, this all‐OPD exhibits a high self‐powered responsivity (R) of over 100 mA W−1 among 500–600 nm and the photocurrent remains about 80% of the original performance after being bent 20 000 circles, and can output steady biosignals for photo‐plethysmography (PPG) application. More importantly, this all‐OPD outputs dual‐polarity photocurrent as it is flipped or folded. Benefitting from the ordered phase distribution and designed Schottky barrier heights, the photogenerated holes will be transferred and collected by nearer electrode, while electrons will be trapped in the thick bulk heterojunction (BHJ) as a result of the long channel. This work offers a new avenue toward developing a multifunctional and ultraflexible all‐OPD with a straightforward all‐solution method, and it is expected to be more compatible in complex application scenarios.

High-Performance Broadband Photoelectrochemical Photodetectors Based on Ultrathin Bi2O2S Nanosheets.

Abstract: Two-dimensional (2D) bismuth oxychalcogenide (Bi2O2X, X refers to S, Se, and Te) is one type of rising semiconductor with excellent electrical transport properties, high photoresponse, and good air stability. However, the research on 2D Bi2O2S is limited. In this work, ultrathin Bi2O2S nanosheets are synthesized by a facile and eco-friendly chemical synthesis method at room temperature. The thickness and lateral sizes are 2-4 nm and 20-40 nm, respectively. The 2D ultrathin Bi2O2S nanosheets have a broad absorption spectrum from ultraviolet (UV) to near-infrared (NIR). Photoelectrochemical (PEC) photodetectors based on 2D Bi2O2S nanosheets are fabricated by a simple drop-casting method. The 2D Bi2O2S-based PEC photodetectors show excellent photodetection performance with a broad photoresponse spectrum from 365 to 850 nm, a high responsivity of 13.0 mA/W, ultrafast response times of 10/45 ms, and good long-term stability at a bias voltage of 0.6 V, which are superior to most 2D material-based PEC photodetectors. Further, the 2D Bi2O2S PEC photodetector can function as a high-performance self-powered broadband photodetector. Moreover, the photoresponse performance can be effectively tuned by the concentration and the kind of electrolyte. Our results demonstrate that 2D Bi2O2S nanosheets hold great promise for application in high-performance optoelectronic devices.

Work‐Function‐Tunable MXenes Electrodes to Optimize p‐CsCu2I3/n‐Ca2Nb3‐xTaxO10 Junction Photodetectors for Image Sensing and Logic Electronics

Abstract: Tunable work function has a high profile for the MXene‐based optoelectronic devices, and surface modification provides the huge potential to shift its Fermi level and modulate the work function. In this work, the window of MXene's work function is engineered from 4.55 to 5.25 eV by surface modification with LiF, Se, and polyethylenimine ethoxylated (PEIE). The vertical p‐CsCu2I3/n‐Ca2Nb3‐xTaxO10 junction photodetectors are constructed on the basis of the above surface‐modified MXenes, which changes the Schottky barrier between n‐Ca2Nb3‐xTaxO10 and the electrodes. In particular, the rectification effect is significantly enhanced by utilizing PEIE‐decorated MXene electrodes, resulting in a high rectification ratio of 16 136 and improved UV responsivity of 81.3 A W–1. Such high‐performance devices based on MXenes electrodes are compatible with the standard clean room fabrication process, realizing large‐scale flexible UV detectors that maintain 80% of the original current after 5000 times bending. Meanwhile, a photodetector array stimulated with UV of different wavelengths is constructed to reveal its potential for image sensing. Finally, functional “AND” and “OR” optoelectronic logic gates are developed for UV communication using Au/CsCu2I3/Ca2Nb3‐xTaxO10/MXene–PEIE photodetectors, enriching the application of MXene‐based optoelectronic devices. This work on tuning MXene work function via surface modification demonstrates that MXene is a promising candidate for future optoelectronics.

Narrowband organic photodetectors – towards miniaturized, spectroscopic sensing

Abstract: Omnipresent quality monitoring in food products, blood-oxygen measurement in lightweight conformal wrist bands, or data-driven automated industrial production: Innovation in many fields is being empowered by sensor technology. Specifically, organic photodetectors (OPDs) promise great advances due to their beneficial properties and low-cost production. Recent research has led to rapid improvement in all performance parameters of OPDs, which are now on-par or better than their inorganic counterparts, such as silicon or indium gallium arsenide photodetectors, in several aspects. In particular, it is possible to directly design OPDs for specific wavelengths. This makes expensive and bulky optical filters obsolete and allows for miniature detector devices. In this review, recent progress of such narrowband OPDs is systematically summarized covering all aspects from narrow-photo-absorbing materials to device architecture engineering. The recent challenges for narrowband OPDs, like achieving high responsivity, low dark current, high response speed, and good dynamic range are carefully addressed. Finally, application demonstrations covering broadband and narrowband OPDs are discussed. Importantly, several exciting research perspectives, which will stimulate further research on organic-semiconductor-based photodetectors, are pointed out at the very end of this review.

Work‐Function‐Tunable MXenes Electrodes to Optimize p‐CsCu ₂ I ₃ /n‐Ca ₂ Nb _3‐ <i> _x </i> Ta <i>

Abstract: Tunable work function has a high profile for the MXene-based optoelectronic devices, and surface modification provides the huge potential to shift its Fermi level and modulate the work function. In this work, the window of MXene's work function is engineered from 4.55 to 5.25 eV by surface modification with LiF, Se, and polyethylenimine ethoxylated (PEIE). The vertical p-CsCu2I3/n-Ca2Nb3-xTaxO10 junction photodetectors are constructed on the basis of the above surface-modified MXenes, which changes the Schottky barrier between n-Ca2Nb3-xTaxO10 and the electrodes. In particular, the rectification effect is significantly enhanced by utilizing PEIE-decorated MXene electrodes, resulting in a high rectification ratio of 16 136 and improved UV responsivity of 81.3 A W–1. Such high-performance devices based on MXenes electrodes are compatible with the standard clean room fabrication process, realizing large-scale flexible UV detectors that maintain 80% of the original current after 5000 times bending. Meanwhile, a photodetector array stimulated with UV of different wavelengths is constructed to reveal its potential for image sensing. Finally, functional “AND” and “OR” optoelectronic logic gates are developed for UV communication using Au/CsCu2I3/Ca2Nb3-xTaxO10/MXene–PEIE photodetectors, enriching the application of MXene-based optoelectronic devices. This work on tuning MXene work function via surface modification demonstrates that MXene is a promising candidate for future optoelectronics.

Narrowband organic photodetectors - towards miniaturized, spectroscopic sensing.

Abstract: Omnipresent quality monitoring in food products, blood-oxygen measurement in lightweight conformal wrist bands, or data-driven automated industrial production: Innovation in many fields is being empowered by sensor technology. Specifically, organic photodetectors (OPDs) promise great advances due to their beneficial properties and low-cost production. Recent research has led to rapid improvement in all performance parameters of OPDs, which are now on-par or better than their inorganic counterparts, such as silicon or indium gallium arsenide photodetectors, in several aspects. In particular, it is possible to directly design OPDs for specific wavelengths. This makes expensive and bulky optical filters obsolete and allows for miniature detector devices. In this review, recent progress of such narrowband OPDs is systematically summarized covering all aspects from narrow-photo-absorbing materials to device architecture engineering. The recent challenges for narrowband OPDs, like achieving high responsivity, low dark current, high response speed, and good dynamic range are carefully addressed. Finally, application demonstrations covering broadband and narrowband OPDs are discussed. Importantly, several exciting research perspectives, which will stimulate further research on organic-semiconductor-based photodetectors, are pointed out at the very end of this review.

Resonance-Induced Stimuli-Responsive Capacity Modulation of Organic Ultralong Room Temperature Phosphorescence.

Abstract: Organic ultralong room temperature phosphorescence (OURTP) materials having stimuli-responsive attributes have attracted great attention due to their great potential in a wide variety of advanced applications. It is of fundamental importance but challengeable to develop stimuli-responsive OURTP materials, especially such materials with modulated optoelectronic properties in a controlled manner probably due to the lack of an authentic construction approach. Here, we propose an effective strategy for OURTP materials with controllably regulated stimuli-responsive properties by engineering the resonance linkage between flexible chain and phosphor units. A quantitative parameter to demonstrate the stimuli-responsive capacity is also established by the responsivity rate constant. The designed OURTP materials demonstrate efficient photoactivated OURTP with lifetimes up to 724 ms and tunable responsivity rate constants ranging from 0.132 to 0.308 min-1 upon continuous UV irradiation. Moreover, the applications of stimuli-responsive resonance OURTP materials have been illustrated by the rewritable paper for snapshot and Morse code for multiple information encryption. Our works, which enable the accomplishment of OURTP materials capable of on-demand manipulated optical properties, demonstrate a viable design to explore smart OURTP materials, giving deep insights into the dynamically stimuli-responsive process.

Chip-integrated van der Waals PN heterojunction photodetector with low dark current and high responsivity

Abstract: Two-dimensional materials are attractive for constructing high-performance photonic chip-integrated photodetectors because of their remarkable electronic and optical properties and dangling-bond-free surfaces. However, the reported chip-integrated two-dimensional material photodetectors were mainly implemented with the configuration of metal-semiconductor-metal, suffering from high dark currents and low responsivities at high operation speed. Here, we report a van der Waals PN heterojunction photodetector, composed of p-type black phosphorous and n-type molybdenum telluride, integrated on a silicon nitride waveguide. The built-in electric field of the PN heterojunction significantly suppresses the dark current and improves the responsivity. Under a bias of 1 V pointing from n-type molybdenum telluride to p-type black phosphorous, the dark current is lower than 7 nA, which is more than two orders of magnitude lower than those reported in other waveguide-integrated black phosphorus photodetectors. An intrinsic responsivity up to 577 mA W-1 is obtained. Remarkably, the van der Waals PN heterojunction is tunable by the electrostatic doping to further engineer its rectification and improve the photodetection, enabling an increased responsivity of 709 mA W-1. Besides, the heterojunction photodetector exhibits a response bandwidth of ~1.0 GHz and a uniform photodetection over a wide spectral range, as experimentally measured from 1500 to 1630 nm. The demonstrated chip-integrated van der Waals PN heterojunction photodetector with low dark current, high responsivity and fast response has great potentials to develop high-performance on-chip photodetectors for various photonic integrated circuits based on silicon, lithium niobate, polymer, etc.

High‐Performance Visible to Near‐Infrared Broadband Bi2O2Se Nanoribbon Photodetectors

Abstract: Owing to its suitable electronic bandgap, excellent air stability, and high carrier mobility at room temperature, low‐dimensional bismuth oxyselenide (Bi2O2Se) has become attractive in the context of visible–near‐infrared (VIS–NIR) detection. However, the high carrier concentration and bolometric effect of Bi2O2Se nanosheets are not conducive to reducing the dark current and improving the response speed, which hinders Bi2O2Se nanosheet‐based photodetectors from achieving an optimal performance. In this study, a Bi2O2Se nanoribbon is controllably synthesized on a fluorophlogopite substrate by means of the chemical vapor deposition approach. Through the use of a Bi2O2Se nanoribbon structure and the application of a Schottky barrier between the Bi2O2Se and Au electrodes, a fast response and low noise photodetector is achieved. More specifically, the response times are 2.1 and 313 µs at 650 and 1550 nm, respectively, and the corresponding optimal detectivities are 3.28 × 1013 and 8.07 × 109 Jones. Furthermore, the device reaches a −3 dB bandwidth of 81 kHz and exhibits a responsivity of 3.2 × 105 A W−1 at 650 nm under a bias of 5 V. This study provides new opportunities for the application of high‐performance VIS–NIR photodetectors.

Enhanced Performance of a Self‐Powered ZnO Photodetector by Coupling LSPR‐Inspired Pyro‐Phototronic Effect and Piezo‐Phototronic Effect

Abstract: Ultraviolet detection is overriding priority in many military and civilian fields. A photodetector can be effectively enhanced by introducing piezo‐phototronic effect, pyro‐phototronic effect, and localized surface plasmon resonance (LSPR). Coupling piezo‐phototronic, pyro‐phototronic, and LSPR effect can be realized in a self‐powered photodetector based on ZnO/CuO nanorods covered with Au nanoparticles (NPs). The influences of LSPR, pyroelectric and external pressure on the performance of devices are thoroughly investigated, respectively. ZnO/CuO/Au devices display the most attractive performance under pressure of 73.7 N. The maxima of responsivity and detectivity are obtained as 0.81 mA W‐1 and 3.3 × 1013 Jones, respectively, under pressure of 73.7 N when detecting weak ultraviolet radiation (140 nW cm‐2). Responsivity and detectivity are dramatically enhanced by 17× and 12× compared to CuO/ZnO devices. Moreover, rise time and fall time reduce from 114/75 ms of a ZnO/CuO device to 18/12 ms of a ZnO/CuO/Au device under pressure of 64.7 N. These results demonstrate that LSPR, pyro‐phototronic, and piezo‐phototronic coupled effect makes greater improvement than the individual effects in the performance of photodetectors. This work probably can be a cornerstone of designing high‐performance photodetectors using other nanomaterial systems as well.

Epitaxial Growth of Vertically Aligned Antimony Selenide Nanorod Arrays for Heterostructure Based Self‐Powered Photodetector

Abstract: Antimony selenide (Sb2Se3) has garnered significant attention with its extraordinary optical and optoelectronic properties for optical and optoelectronic devices such as broadband photodetectors. The trends emerge in the synthesis of Sb2Se3 over a semiconducting substrate for the direct formation of heterostructures, which facilitate a pn junction for self‐powered photodetector. 1D Sb2Se3 nanorods are preferred to boost the charge carrier transport along the longitudinal direction as well as the optical absorption by light trapping. Great challenges remain for the vertical growth of nanorods. In this work, the precisely vertical alignment of Sb2Se3 nanorod arrays has been achieved in an epitaxial growth manner by selecting a lattice‐matching substrate, namely, boron‐doped ZnO (110) surface. The directly grown boron‐doped ZnO/Sb2Se3 nanorod arrays heterostructure leads to a high‐performance broadband photodetector. Eventually, the device demonstrates extraordinary figure‐of‐merit parameters, i.e., responsivity, on/off ratio, and specific detectivity. Furthermore, device simulation predicts the theoretical limit of the photodetector performances on the condition of suppressed defect density of the Sb2Se3. These results may shed light on the investigation of controlled growth of low‐dimensional materials, self‐powered photodetectors, and related optic and optoelectronic devices.

High-Performance, Polarization-Sensitive, Long-Wave Infrared Photodetection via Photothermoelectric Effect with Asymmetric van der Waals Contacts.

Abstract: Long-wavelength infrared (LWIR) photodetection is important for heat-seeking technologies, such as thermal imaging, all-weather surveillance, and missile guidance. Among various detection techniques, photothermoelectric (PTE) detectors are promising in that they can realize ultra-broadband photodetection at room temperature without an external power supply. However, their performance in terms of speed, responsivity, and noise level in the LWIR regime still needs further improvement. Here, we demonstrated a high-performance PTE photodetector based on low-symmetry palladium selenide (PdSe2) with asymmetric van der Waals contacts. The temperature gradient induced by asymmetric van der Waals contacts even under global illumination drives carrier diffusion to produce a photovoltage via the PTE effect. A responsivity of over 13 V/W, a response time of ∼50 μs, and a noise equivalent power of less than 7 nW/Hz1/2 are obtained in the 4.6-10.5 μm regime at room temperature. Furthermore, due to the anisotropic absorption of PdSe2, the detector exhibits a linear polarization angle sensitive response with an anisotropy ratio of 2.06 at 4.6 μm and 1.21 at 10.5 μm, respectively. Our proposed device architecture provides an alternative strategy to design high-performance photodetectors in the LWIR regime by utilizing van der Waals layered materials.

High Responsivity Circular Polarized Light Detectors based on Quasi Two-Dimensional Chiral Perovskite Films

Abstract: Circularly polarized light (CPL) has considerable technological potential, from quantum computing to bioimaging. To maximize the opportunity, high performance photodetectors that can directly distinguish left-handed and right-handed circularly polarized light are needed. Hybrid organic–inorganic perovskites containing chiral organic ligands are an emerging candidate for the active material in CPL photodetecting devices, but current studies suggest there to be a trade-off between the ability to differentially absorb CPL and photocurrent responsivity in chiral perovskites devices. Here, we report a CPL detector based on quasi two-dimensional (quasi-2D) chiral perovskite films. We find it is possible to generate materials where the circular dichroism (CD) is comparable in both 2D and quasi-2D films, while the responsivity of the photodetector improves for the latter. Given this, we are able to showcase a CPL photodetector that exhibits both a high dissymmetry factor of 0.15 and a high responsivity of 15.7 A W–1. We believe our data further advocates the potential of chiral perovskites in CPL-dependent photonic technologies.

Polarization Sensitive Solar‐Blind Ultraviolet Photodetectors Based on Ultrawide Bandgap KNb3O8 Nanobelt with Fringe‐Like Atomic Lattice

Abstract: Low‐dimensional ultrawide bandgap semiconductors demonstrate great potential in fabricating solar‐blind ultraviolet photodetectors. However, the widespread use of detectors is still limited by the low responsivity, large noise, and dark current, and especially few detectors can fulfill the solar‐blind ultraviolet detection and the polarization dependence simultaneously. Herein, a polarization sensitive solar‐blind ultraviolet photodetector based on ultrathin KNb3O8 nanobelts synthesized via chemical vapor deposition growth, is reported. By selecting suitable substrate and tuning the growth temperature, the nonlayered KNb3O8 crystal is grown into the quasi‐1D ultrathin nanobelt with thickness in the range of 4.8–120 nm. Density functional theory calculations and experimental results indicate that the ultrathin KNb3O8 nanobelt possesses an ultrawide bandgap (4.15 eV) as well as unusual in‐plane structural anisotropy. Benefiting from the above features, the ultrathin KNb3O8 nanobelt‐based device exhibits superior photodetection performances with high responsivity (30 A W−1), high detectivity (5.95 × 1011 Jones), and ultralow dark current (7.1 × 10−15 A) in the solar‐blind ultraviolet region (230–280 nm). In addition, the KNb3O8 photodetector displays strong polarization sensitive photoresponse with a linear dichroic ratio of 1.62 at 254 nm. With these remarkable features, the ultrathin KNb3O8 nanobelt provides great opportunities for designing the next‐generation multifunctional solar‐blind ultraviolet optoelectronic devices.

Chip-integrated van der Waals PN heterojunction photodetector with low dark current and high responsivity

Abstract: Two-dimensional materials are attractive for constructing high-performance photonic chip-integrated photodetectors because of their remarkable electronic and optical properties and dangling-bond-free surfaces. However, the reported chip-integrated two-dimensional material photodetectors were mainly implemented with the configuration of metal-semiconductor-metal, suffering from high dark currents and low responsivities at high operation speed. Here, we report a van der Waals PN heterojunction photodetector, composed of p-type black phosphorous and n-type molybdenum telluride, integrated on a silicon nitride waveguide. The built-in electric field of the PN heterojunction significantly suppresses the dark current and improves the responsivity. Under a bias of 1 V pointing from n-type molybdenum telluride to p-type black phosphorous, the dark current is lower than 7 nA, which is more than two orders of magnitude lower than those reported in other waveguide-integrated black phosphorus photodetectors. An intrinsic responsivity up to 577 mA W-1 is obtained. Remarkably, the van der Waals PN heterojunction is tunable by the electrostatic doping to further engineer its rectification and improve the photodetection, enabling an increased responsivity of 709 mA W-1. Besides, the heterojunction photodetector exhibits a response bandwidth of ~1.0 GHz and a uniform photodetection over a wide spectral range, as experimentally measured from 1500 to 1630 nm. The demonstrated chip-integrated van der Waals PN heterojunction photodetector with low dark current, high responsivity and fast response has great potentials to develop high-performance on-chip photodetectors for various photonic integrated circuits based on silicon, lithium niobate, polymer, etc.

Enhanced Photogating Effect in Graphene Photodetectors via Potential Fluctuation Engineering.

Abstract: The photogating effect in hybrid structures has manifested itself as a reliable and promising approach for photodetectors with ultrahigh responsivity. A crucial factor of the photogating effect is the built-in potential at the interface, which controls the separation and harvesting of photogenerated carriers. So far, the primary efforts of designing the built-in potential rely on discovering different materials and developing multilayer structures, which may raise problems in the compatibility with the standard semiconductor production line. Here, we report an enhanced photogating effect in a monolayer graphene photodetector based on a structured substrate, where the built-in potential is established by the mechanism of potential fluctuation engineering. We find that the enhancement factor of device responsivity is related to a newly defined parameter, namely, fluctuation period rate (Pf). Compared to the device without a nanostructured substrate, the responsivity of the device with an optimized Pf is enhanced by 100 times, reaching a responsivity of 240 A/W and a specific detectivity, D*, of 3.4 × 1012 Jones at 1550 nm wavelength and room temperature. Our experimental results are supported by both theoretical analysis and numerical simulation. Since our demonstration of the graphene photodetectors leverages the engineering of structures with monolayer graphene rather than materials with a multilayer complex structure. it should be universal and applicable to other hybrid photodetectors.

High Responsivity Si-Ge Waveguide Avalanche Photodiodes Enhanced by Loop Reflector

Abstract: We present a loop reflector-assisted silicon-germanium waveguide avalanche photodiode with improved responsivity. Compared to the same APD without the reflector, it has 1.49 times higher responsivity, $\sim$ 1.12 A/W, without compromising the speed performance. It exhibits a 3 dB-bandwidth of $\sim$ 25 GHz, a build-up time limited gain-bandwidth product of $\sim$ 296 GHz, a highest gain-bandwidth product of $\sim$ 497 GHz. Clear eye diagrams are measured at both 32 Gbps NRZ and 64 Gbps PAM4 modulation, and a 1 $\sim$ 2 dB better sensitivity up to −15.7 dBm with 32 Gbps NRZ at a BER of 2.4 $\times 10^{-4}$ .

Ferro-Pyro-Phototronic Effect in Monocrystalline 2D Ferroelectric Perovskite for High-Sensitive, Self-Powered, and Stable Ultraviolet Photodetector.

Abstract: 2D hybrid perovskite ferroelectrics have drawn great attention in the field of photodetection, because the spontaneous polarization-induced built-in electric field can separate electron-hole pairs, and makes self-powered photodetection possible. However, most of the 2D hybrid perovskite-based photodetectors focused on the detection of visible light, and only a few reports realized the self-powered and sensitive ultraviolet (UV) detection using wide bandgap hybrid perovskites. Here, 2D ferroelectric PMA2PbCl4 monocrystalline microbelt (MMB)-based PDs are demonstrated. By using the ferro-pyro-phototronic effect, the self-powered Ag/Bi/2D PMA2PbCl4 MMB/Bi/Ag PDs show a high photoresponsivity up to 9 A/W under 320 nm laser illumination, which is much higher than those of previously reported self-powered UV PDs. Compared with responsivity induced by the photovoltaic effect, the responsivity induced by the ferro-pyro-phototronic effect is 128 times larger. The self-powered PD also shows fast response and recovery speed, with the rise time and fall time of 162 and 226 μs, respectively. More importantly, the 2D PMA2PbCl4 MMB-based PDs with Bi/Ag electrode exhibit significant stability when subjected to high humidity, continuous laser illumination, and thermal conditions. Our findings would shed light on the ferro-pyro-phototronic-effect-based devices, and provide a good method for high-performance UV detection.

Temperature-dependent photodetection behavior of AlGaN/GaN-based ultraviolet phototransistors

Abstract: In this work, we investigated the temperature-dependent photodetection behavior of a high-performance AlGaN/GaN-based ultraviolet phototransistor (UVPT) operating under 265 nm illumination. As the temperature continuously rises from room temperature to 250 °C, the photocurrent of a device increases in the beginning but suffers from degradation afterwards. This can be explained by the competing process between the generation and recombination rate of photo-induced carriers in the UVPT at room and high temperatures. Intriguingly, we found that the optimal operating temperature for our UVPT is around 50 °C, featuring a high peak responsivity of 1.52 × 105 A/W under a light intensity of 45 μW/cm2. Furthermore, the photoresponse time of our UVPT is also highly temperature-dependent, exhibiting the shortest rise time of 50 ms at 100 °C while the decay time is monotonically reduced as the temperature rises to 250 °C. Notably, our AlGaN/GaN-based UVPTs exhibit ultra-high responsivity at high temperatures, which have outperformed those earlier reported UV photodetectors in the form of different device architectures, highlighting the great potential of such device configurations for harsh environment applications.

Photomultiplication‐Type Organic Photodetectors for Near‐Infrared Sensing with High and Bias‐Independent Specific Detectivity

Abstract: Highly responsive organic photodetectors allow a plethora of applications in fields like imaging, health, security monitoring, etc. Photomultiplication‐type organic photodetectors (PM‐OPDs) are a desirable option due to their internal amplification mechanism. However, for such devices, significant gain and low dark currents are often mutually excluded since large operation voltages often induce high shot noise. Here, a fully vacuum‐processed PM‐OPD is demonstrated using trap‐assisted electron injection in BDP‐OMe:C60 material system. By applying only −1 V, compared with the self‐powered working condition, the responsivity is increased by one order of magnitude, resulting in an outstanding specific detectivity of ≈1013 Jones. Remarkably, the superior detectivity in the near‐infrared region is stable and almost voltage‐independent up to −10 V. Compared with two photovoltaic‐type photodetectors, these PM‐OPDs exhibit the great potential to be easily integrated with state‐of‐the‐art readout electronics in terms of their high responsivity, fast response speed, and bias‐independent specific detectivity. The employed vacuum fabrication process and the easy‐to‐adapt PM‐OPD concept enable seamless upscaling of production, paving the way to a commercially relevant photodetector technology.