Showing papers on "Responsivity published in 2021"

Self-Powered MXene/GaN van der Waals Heterojunction Ultraviolet Photodiodes with Superhigh Efficiency and Stable Current Outputs

Abstract: A self-powered, high-performance Ti3 C2 Tx MXene/GaN van der Waals heterojunction (vdWH)-based ultraviolet (UV) photodiode is reported. Such integration creates a Schottky junction depth that is larger than the UV absorption depth to sufficiently separate the photoinduced electron/hole pairs, boosting the peak internal quantum efficiency over the unity and the external quantum efficiency over 99% under weak UV light without bias. The proposed Ti3 C2 Tx /GaN vdWH UV photodiode demonstrates pronounced photoelectric performances working in self-powered mode, including a large responsivity (284 mA W-1 ), a high specific detectivity (7.06 × 1013 Jones), and fast response speed (rise/decay time of 7.55 µs/1.67 ms). Furthermore, the remarkable photovoltaic behavior leads to an impressive power conversion efficiency of 7.33% under 355 nm UV light illumination. Additionally, this work presents an easy-processing spray-deposition route for the fabrication of large-area UV photodiode arrays that exhibit highly uniform cell-to-cell performance. The MXene/GaN photodiode arrays with high-efficiency and self-powered ability show high potential for many applications, such as energy-saving communication, imaging, and sensing networks.

Ultrabroadband and High-Detectivity Photodetector Based on WS2/Ge Heterojunction through Defect Engineering and Interface Passivation.

Abstract: Broadband photodetectors are of great importance for numerous optoelectronic applications. Two-dimensional (2D) tungsten disulfide (WS2), an important family member of transition-metal dichalcogenides (TMDs), has shown great potential for high-sensitivity photodetection due to its extraordinary properties. However, the inherent large bandgap of WS2 and the strong interface recombination impede the actualization of high-sensitivity broadband photodetectors. Here, we demonstrate the fabrication of an ultrabroadband WS2/Ge heterojunction photodetector through defect engineering and interface passivation. Thanks to the narrowed bandgap of WS2 induced by the vacancy defects, the effective surface modification with an ultrathin AlOx layer, and the well-designed vertical n-n heterojunction structure, the WS2/AlOx/Ge photodetector exhibits an excellent device performance in terms of a high responsivity of 634.5 mA/W, a large specific detectivity up to 4.3 × 1011 Jones, and an ultrafast response speed. Significantly, the device possesses an ultrawide spectral response spanning from deep ultraviolet (200 nm) to mid-wave infrared (MWIR) of 4.6 μm, along with a superior MWIR imaging capability at room temperature. The detection range has surpassed the WS2-based photodetectors in previous reports and is among the broadest for TMD-based photodetectors. Our work provides a strategy for the fabrication of high-performance ultrabroadband photodetectors based on 2D TMD materials.

Highly sensitive solar-blind deep ultraviolet photodetector based on graphene/PtSe2/β-Ga2O3 2D/3D Schottky junction with ultrafast speed

Abstract: There is an emerging need for high-sensitivity solar-blind deep ultraviolet (DUV) photodetectors with an ultra-fast response speed. Although nanoscale devices based on Ga2O3 nanostructures have been developed, their practical applications are greatly limited by their slow response speed as well as low specific detectivity. Here, the successful fabrication of two-/three-dimensional (2D/3D) graphene (Gr)/PtSe2/β-Ga2O3 Schottky junction devices for high-sensitivity solar-blind DUV photodetectors is demonstrated. Benefitting from the high-quality 2D/3D Schottky junction, the vertically stacked structure, and the superior-quality transparent graphene electrode for effective carrier collection, the photodetector is highly sensitive to DUV light illumination and achieves a high responsivity of 76.2 mA/W, a large on/off current ratio of ~ 105, along with an ultra-high ultraviolet (UV)/visible rejection ratio of 1.8 × 104. More importantly, it has an ultra-fast response time of 12 µs and a remarkable specific detectivity of ~ 1013 Jones. Finally, an excellent DUV imaging capability has been identified based on the Gr/PtSe2/β-Ga2O3 Schottky junction photodetector, demonstrating its great potential application in DUV imaging systems.

Ultra-fast germanium photodiode with 3-dB bandwidth of 265 GHz

Abstract: On a scalable silicon technology platform, we demonstrate photodetectors matching or even surpassing state-of-the-art III–V devices. As key components in high-speed optoelectronics, photodetectors with bandwidths greater than 100 GHz have been a topic of intense research for several decades. Solely InP-based detectors could satisfy the highest performance specifications. Devices based on other materials, such as germanium-on-silicon devices, used to lag behind in speed, but enabled complex photonic integrated circuits and co-integration with silicon electronics. Here we demonstrate waveguide-coupled germanium photodiodes with optoelectrical 3-dB bandwidths of 265 GHz and 240 GHz at a photocurrent of 1 mA. This outstanding performance is achieved by a novel device concept in which a germanium fin is sandwiched between complementary in situ-doped silicon layers. Our photodetectors show internal responsivities of 0.3 A W−1 (265 GHz) and 0.45 A W−1 (240 GHz) at a wavelength of 1,550 nm. The internal bandwidth–efficiency product of the latter device is 86 GHz. Low dark currents of 100–200 nA are obtained from these ultra-fast photodetectors. By sandwiching a germanium fin between complementary in situ-doped silicon layers, a waveguide-coupled germanium photodiode with a 3-dB bandwidth of 265 GHz, accompanied by high responsivity and low dark current, is realized.

Pt/AlGaN Nanoarchitecture: Toward High Responsivity, Self-Powered Ultraviolet-Sensitive Photodetection

Abstract: Energy-saving photodetectors are the key components in future photonic systems. Particularly, self-powered photoelectrochemical-type photodetectors (PEC-PDs), which depart completely from the classical solid-state junction device, have lately intrigued intensive interest to meet next-generation power-independent and environment-sensitive photodetection. Herein, we construct, for the first time, solar-blind PEC PDs based on self-assembled AlGaN nanostructures on silicon. Importantly, with the proper surface platinum (Pt) decoration, a significant boost of photon responsivity by more than an order of magnitude was achieved in the newly built Pt/AlGaN nanoarchitectures, demonstrating strikingly high responsivity of 45 mA/W and record fast response/recovery time of 47/20 ms without external power source. Such high solar-blind photodetection originates from the unparalleled material quality, fast interfacial kinetics, as well as high carrier separation efficiency which suggests that embracement of defect-free wide-bandgap semiconductor nanostructures with appropriate surface decoration offers an unprecedented opportunity for designing future energy-efficient and large-scale optoelectronic systems on a silicon platform.

Blackbody-sensitive room-temperature infrared photodetectors based on low-dimensional tellurium grown by chemical vapor deposition.

Abstract: Blackbody-sensitive room-temperature infrared detection is a notable development direction for future low-dimensional infrared photodetectors. However, because of the limitations of responsivity and spectral response range for low-dimensional narrow bandgap semiconductors, few low-dimensional infrared photodetectors exhibit blackbody sensitivity. Here, highly crystalline tellurium (Te) nanowires and two-dimensional nanosheets were synthesized by using chemical vapor deposition. The low-dimensional Te shows high hole mobility and broadband detection. The blackbody-sensitive infrared detection of Te devices was demonstrated. A high responsivity of 6650 A W-1 (at 1550-nm laser) and the blackbody responsivity of 5.19 A W-1 were achieved. High-resolution imaging based on Te photodetectors was successfully obtained. All the results suggest that the chemical vapor deposition-grown low-dimensional Te is one of the competitive candidates for sensitive focal-plane-array infrared photodetectors at room temperature.

Broadband Ultraviolet Self-Powered Photodetector Constructed on Exfoliated β-Ga2O3/CuI Core-Shell Microwire Heterojunction with Superior Reliability.

Abstract: A heterojunction is an essential strategy for multispectral energy-conservation photodetection for its ability to separate photogenerated electron-hole pairs and tune the absorption edge by selecting semiconductors with appropriate bandgaps. A broadband ultraviolet (200-410 nm) self-powered photodetector is constructed on the exfoliated β-Ga2O3/CuI core-shell microwire heterostructure. Benefiting from the photovoltaic and photoconductive effects, our device performs an excellent ultraviolet (UV) discriminability with a UVC/visible rejection ratio (R225/R600) of 8.8 × 103 and a UVA/visible rejection ratio (R400/R600) of 2.7 × 102, and a self-powered photodetection with a responsivity of 8.46 mA/W, a detectivity of 7.75 × 1011 Jones, an on/off switching ratio of 4.0 × 103, and a raise/decay speed of 97.8/28.9 ms under UVC light. Even without encapsulation, the photodetector keeps a superior stability over ten months. The intrinsically physical insights of the device behaviors are investigated via energy band diagrams, and the charge carrier transfer characteristics of the β-Ga2O3/CuI interface are predicted by first principle calculation.

Fabrication of 1D Te/2D ReS2 Mixed-Dimensional van der Waals p-n Heterojunction for High-Performance Phototransistor.

Abstract: The superior optical and electronic properties of the two-dimensional (2D) rhenium disulfide (ReS2) makes it suitable for nanoelectronic and optoelectronic applications. However, the internal defects coupled with with the low mobility and light-absorbing capability of ReS2 impede its utilization in high-performance photodetectors. Fabrication of mixed-dimensional heterojunctions is an alternative method for designing high-performance hybrid photodetectors. This study proposes a mixed-dimensional van der Waals (vdW) heterojunction photodetector, containing high-performance one-dimensional (1D) p-type tellurium (Te) and 2D n-type ReS2, developed by depositing Te nanowires on ReS2 nanoflake using the dry transfer method. It can improve the injection and separation efficiency of photoexcited electron-hole pairs due to the type II p-n heterojunction formed at the ReS2 and Te interface. The proposed heterojunction device is sensitive to visible-light sensitivity (632 nm) with an ultrafast photoresponse (5 ms), high responsivity (180 A/W), and specific detectivity (109), which is superior to the pristine Te and ReS2 photodetectors. As compared to the ReS2 device, the responsivity and response speed is better by an order of magnitude. These results demonstrate the fabrication and application potential of Te/ReS2 mixed-dimensional heterojunction for high-performance optoelectronic devices and sensors.

High and flat spectral responsivity of quartz tuning fork used as infrared photodetector in tunable diode laser spectroscopy

Abstract: Infrared laser technology over the last decades has led to an increasing demand for optical detectors with high sensitivity and a wide operative spectral range suitable for spectroscopic applications. In this work, we report on the performance of a custom quartz tuning fork used as a sensitive and broadband infrared photodetector for absorption spectroscopy. The photodetection process is based on light impacting on the tuning fork and creating a local temperature increase that generates a strain field. This light-induced, thermoelastic conversion produces an electrical signal proportional to the absorbed light intensity due to quartz piezoelectricity. A finite-element-method analysis was used to relate the energy release with the induced thermal distribution. To efficiently exploit the photo-induced thermoelastic effects in the low-absorbance spectral region of quartz also, chromium/gold layers, acting as opaque surface, have been deposited on the quartz surface. To demonstrate the flat response as photodetectors, a custom tuning fork, having a fundamental resonance frequency of 9.78 kHz and quality factor of 11 500 at atmospheric pressure, was employed as photodetector in a tunable diode laser absorption spectroscopy setup and tested with five different lasers with emission wavelength in the 1.65–10.34 μm range. A spectrally flat responsivity of ∼2.2 kV/W was demonstrated, corresponding to a noise-equivalent power of 1.5 nW/√Hz, without employing any thermoelectrical cooling systems. Finally, a heterodyne detection scheme was implemented in the tunable diode laser absorption spectroscopy setup to retrieve the resonance properties of the quartz tuning fork together with the gas concentration in a single, fast measurement.

Inch-sized high-quality perovskite single crystals by suppressing phase segregation for light-powered integrated circuits

Abstract: The triple-cation mixed-halide perovskite (FA x MA y Cs1-x-y )Pb(IzBr1-z )3 (FAMACs) is the best composition for thin-film solar cells Unfortunately, there is no effective method to prepare large single crystals (SCs) for more advanced applications Here, we report an effective additive strategy to grow 2-inch-sized high-quality FAMACs SCs It is found that the judiciously selected reductant [formic acid (FAH)] effectively minimizes iodide oxidation and cation deprotonation responsible for phase segregation Consequently, the FAMACs SC shows more than fivefold enhancement in carrier lifetimes, high charge mobility, long carrier diffusion distance, as well as superior uniformity and long-term stability, making it possible for us to design high-performance self-powered integrated circuit photodetector The device exhibits large responsivity, high photoconductive gain, excellent detectivity, and fast response speed; all values are among the highest reported to date for planar-type single-crystalline perovskite photodetectors Furthermore, an integrated imaging system is fabricated on the basis of 12 × 12 pixelated matrixes of the single-crystal photodetectors

Demonstration of AlGaN/GaN-based ultraviolet phototransistor with a record high responsivity over 3.6 × 107 A/W

Abstract: In this work, we demonstrate a high-performance ultraviolet phototransistor (UVPT) based on the AlGaN/GaN high-electron mobility transistor (HEMT) configuration. When the device is biased at off state, the peak photoresponsivity (R) of 3.6 × 107 A/W under 265 nm illumination and 1.0 × 106 A/W under 365 nm illumination can be obtained. Those two R values are one of the highest among the reported UVPTs at the same detection wavelength under off-state conditions. In addition, we investigate the gate-bias (VGS) dependent photoresponse of the fabricated device with the assistance of band structure analysis. It was found that a more negative VGS can significantly reduce the rise/decay time for 265 nm detection, especially under weak illumination. This can be attributed to a largely enhanced electric field in the absorptive AlGaN barrier that pushes the photo-generated carriers rapidly into the GaN channel. In contrast, the VGS has little impact on the switching time for 365 nm photodetection, since the GaN channel has a larger absorption depth and the entire UVPT simply acts as a photoconductive-type device. In short, the proposed AlGaN/GaN HEMT structure with the superior photodetection performance paves the way for the development of next generation UVPTs.

High-Performance Harsh-Environment-Resistant GaOX Solar-Blind Photodetectors via Defect and Doping Engineering.

Abstract: Gallium oxide (Ga2 O3 ), with an ultrawide bandgap, is currently regarded as one of the most promising materials for solar-blind photodetectors (SBPDs), which are greatly demanded in harsh environment, such as the situations of space exploration and flame prewarning. However, realization of high-performance SBPDs with high tolerance towards harsh environments based on low-cost Ga2 O3 material faces great challenges. Here, defect and doping (DD) engineering towards amorphous GaOX (a-GaOX ) has been proposed to obtain ultrasensitive SBPDs for harsh condition application. Serious oxygen deficiency and doping compensation of the engineered a-GaOX film ensure the high response currents and low dark currents, respectively. Annealing item in nitrogen of DD engineering also incurs the recrystallization of material, formation of nanopores by oxygen escape, and suppression of sub-bandgap defect states. As a result, the tailored GaOX SBPD based on DD engineering not only harvests a record-high responsivity rejection ratio (R254 nm /R365 nm ) of 1.8×107 , 102 times higher detectivity, and 2×102 times faster decay speed than the control device, but also keeps a high responsivity, high photo-to-dark current ratio, and sharp imaging capability even at high temperature (280°C) or high bias (100 V). The proposed DD engineering provides an effective strategy towards highly harsh-environment-resistant GaOX SBPDs. This article is protected by copyright. All rights reserved.

Tunnel field-effect transistors for sensitive terahertz detection

Abstract: The rectification of electromagnetic waves to direct currents is a crucial process for energy harvesting, beyond-5G wireless communications, ultra-fast science, and observational astronomy. As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. Here, we address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG’s electrically tunable band structure, we create a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation is then down-converted by the tunnel junction nonlinearity, resulting in high responsivity (>4 kV/W) and low-noise (0.2 pW/ $$\sqrt{{\rm{Hz}}}$$ ) detection. We demonstrate how switching from intraband Ohmic to interband tunneling regime can raise detectors’ responsivity by few orders of magnitude, in agreement with the developed theory. Our work demonstrates a potential application of tunnel transistors for THz detection and reveals BLG as a promising platform therefor. Here, a strong nonlinearity of the gate-induced tunnel junction in bilayer graphene is used for efficient terahertz detection. The improved signal-to-noise ratio, as compared to conventional detectors, offers the application of steep-switching transistors in terahertz technology.

Moisture-Triggered Self-Healing Flexible Perovskite Photodetectors with Excellent Mechanical Stability.

Abstract: Flexible devices are urgently required to meet the demands of next-generation optoelectronic devices and metal halide perovskites are proven to be suitable materials for realizing flexible photovoltaic devices. However, the tolerance to moisture corrosion and repeated mechanical bending remains a critical challenge for flexible perovskite devices. Herein, a self-healing formamidinium lead iodide (FAPbI3 ) film is fabricated to cure mechanical damage by absorbing moisture from the surrounding environment. A poly(vinyl alcohol) microscaffold is designed not only to stabilize the black phase of the FAPbI3 film but also to endow it with self-healing ability in a humid environment. The photodetector based on a self-healing film exhibits a high responsivity of 11.3 A W-1 and recovers to over 90% of the initial responsivity after the self-healing process. This work provides an effective self-healing strategy to stabilize the operation of flexible perovskite devices under normal high-humidity environmental conditions.

Oxygen vacancies modulating the photodetector performances in ε-Ga2O3 thin films

Abstract: By acting as the trapping centers during charge carrier transfer, oxygen vacancy (VO) plays a critical role in oxide photoelectric devices. Herein, a post-annealing method was introduced to perfect the photodetection performances of e-Ga2O3 photodetectors (PDs) by improving the film quality and modulating the VO defect concentration. The native oxygen-deficient e-Ga2O3 epitaxial films fabricated via metal–organic chemical vapor deposition become highly dense and VO-less after oxidation annealing, leading to an enhanced performance, while they become VO-rich after reduction annealing to depress the PD property. Compared with the pristine PD, the crucial parameters of the devices with a lower VO concentration have been improved by 1–6 magnitude with a high photo-to-dark current ratio of 1.06 × 108, a large responsivity of 1.368 A W−1, an excellent detectivity of 9.13 × 1014 Jones, a superior linear dynamic range of 176.7 dB and an outstanding external quantum efficiency of 666.5% and a record-high rejection ratio (R240/R400) of 1.80 × 107. As the VO defect is commonly ubiquitous in oxide materials, our investigation of regulating the VO concentrations in e-Ga2O3 and then exerting influences on the PD capabilities will provide principles for designing high-performance photoelectric devices.

MoS2 Based Photodetectors: A Review.

Abstract: Photodetectors based on transition metal dichalcogenides (TMDs) have been widely reported in the literature and molybdenum disulfide (MoS2) has been the most extensively explored for photodetection applications. The properties of MoS2, such as direct band gap transition in low dimensional structures, strong light-matter interaction and good carrier mobility, combined with the possibility of fabricating thin MoS2 films, have attracted interest for this material in the field of optoelectronics. In this work, MoS2-based photodetectors are reviewed in terms of their main performance metrics, namely responsivity, detectivity, response time and dark current. Although neat MoS2-based detectors already show remarkable characteristics in the visible spectral range, MoS2 can be advantageously coupled with other materials to further improve the detector performance Nanoparticles (NPs) and quantum dots (QDs) have been exploited in combination with MoS2 to boost the response of the devices in the near ultraviolet (NUV) and infrared (IR) spectral range. Moreover, heterostructures with different materials (e.g., other TMDs, Graphene) can speed up the response of the photodetectors through the creation of built-in electric fields and the faster transport of charge carriers. Finally, in order to enhance the stability of the devices, perovskites have been exploited both as passivation layers and as electron reservoirs.

Solution-processed and self-powered photodetector in vertical architecture using mixed-halide perovskite for highly sensitive UVC detection

Abstract: In this study, a self-powered lead-halide perovskite-based deep-ultraviolet (UV) photodetector was prepared using a solution process. A heterojunction of mixed (FAPbI3)0.97(MAPbBr3)0.03 perovskite was utilized as the photo-absorber layer, and spiro-OMeTAD was utilized as the hole injection layer in a vertical structure. The device exhibited an outstanding on/off photocurrent ratio of more than 103, a good responsivity of 52.68 mA W−1, and a high detectivity of 4.65 × 1011 Jones under 254 nm UV illumination without an external bias. Moreover, the detector demonstrated superior stability while retaining a quick response speed after three weeks of storage in ambient air without encapsulation. Thus, the present study has developed a promising photodetector for several applications in the deep-UV region.

Ultrahigh Deep-Ultraviolet Responsivity of a β-Ga2O3/MgO Heterostructure-Based Phototransistor

Abstract: Deep-ultraviolet (DUV) photodetectors based on wide-band-gap semiconductors have attracted significant interest across a wide range of applications in the industrial, biological, environmental, and...

An Ultrafast WSe2 Photodiode Based on a Lateral p-i-n Homojunction.

Abstract: High-quality homogeneous junctions are of great significance for developing transition metal dichalcogenides (TMDs) based electronic and optoelectronic devices. Here, we demonstrate a lateral p-type/intrinsic/n-type (p-i-n) homojunction based multilayer WSe2 diode. The photodiode is formed through selective doping, more specifically by utilizing self-aligning surface plasma treatment at the contact regions, while keeping the WSe2 channel intrinsic. Electrical measurements of such a diode reveal an ideal rectifying behavior with a current on/off ratio as high as 1.2 × 106 and an ideality factor of 1.14. While operating in the photovoltaic mode, the diode presents an excellent photodetecting performance under 450 nm light illumination, including an open-circuit voltage of 340 mV, a responsivity of 0.1 A W-1, and a specific detectivity of 2.2 × 1013 Jones. Furthermore, benefiting from the lateral p-i-n configuration, the slow photoresponse dynamics including the photocarrier diffusion in undepleted regions and photocarrier trapping/detrapping due to dopants or doping process induced defect states are significantly suppressed. Consequently, a record-breaking response time of 264 ns and a 3 dB bandwidth of 1.9 MHz are realized, compared with the previously reported TMDs based photodetectors. The above-mentioned desirable properties, together with CMOS compatible processes, make this WSe2p-i-n junction diode promising for future applications in self-powered high-frequency weak signal photodetection.

Sensitivity of Field-Effect Transistor-Based Terahertz Detectors

Abstract: This paper presents an overview of the different methods used for sensitivity (i.e., responsivity and noise equivalent power) determination of state-of-the-art field-effect transistor-based THz detectors/sensors. We point out that the reported result may depend very much on the method used to determine the effective area of the sensor, often leading to discrepancies of up to orders of magnitude. The challenges that arise when selecting a proper method for characterisation are demonstrated using the example of a 2×7 detector array. This array utilises field-effect transistors and monolithically integrated patch antennas at 620 GHz. The directivities of the individual antennas were simulated and determined from the measured angle dependence of the rectified voltage, as a function of tilting in the E- and H-planes. Furthermore, this study shows that the experimentally determined directivity and simulations imply that the part of radiation might still propagate in the substrate, resulting in modification of the sensor effective area. Our work summarises the methods for determining sensitivity which are paving the way towards the unified scientific metrology of FET-based THz sensors, which is important for both researchers competing for records, potential users, and system designers.

Photoresponse improvement of mixed-dimensional 1D–2D GaAs photodetectors by incorporating constructive interface states

Abstract: Mixed-dimensional optoelectronic devices bring new challenges and opportunities over the design of conventional low-dimensional devices. In this work, we develop unreported mixed-dimensional GaAs photodetectors by utilizing 1D GaAs nanowires (NWs) and 2D GaAs non-layered sheets (2DNLSs) as active device materials. The fabricated photodetector exhibits a responsivity of 677 A W-1 and a detectivity of 8.69 × 1012 cm Hz0.5 W-1 under 532 nm irradiation, which are already much better than those of state-of-the-art low-dimensional GaAs photodetectors. It is found that this unique device structure is capable of converting the notoriously harmful surface states of NWs and 2DNLSs into their constructive interface states, which contribute to the formation of quasi-type-II band structures and electron wells in the device channel for the substantial performance enhancement. More importantly, these interface states are demonstrated to be insensitive to ambient environments, indicating the superior stability of the device. All these results evidently illustrate a simple but effective way to utilize the surface states of nanomaterials to achieve the high-performance photodetectors.

Broadband and sensitive two-dimensional halide perovskite photodetector for full-spectrum underwater optical communication

Abstract: Full-spectrum underwater optical communication (UOC) is of great significance for major strategic needs including resource development, scientific exploration, and homeland security. As the core of the full-spectrum UOC system, photodetectors (PDs) are plagued by stringent requirements including a broadband response, intrinsic water resistance, and a high detectivity. In this work, two-dimensional (2D) halide perovskites (HPs) and corresponding PDs are constructed by stearamine (SA), representing the rarely explored long-chain aliphatic amine series, to own waterproofness, ultralow noise, and superior optoelectronic performance, which consequently enable a high suitability for UOC. By dimensionality and composition modulations to extend the absorption onset down to 1.5 eV, a broadband response covering the entire transmission window of water (> 1.55 eV) for full- spectrum UOC can be obtained. Besides, featuring a high responsivity of 3.27 A·W−1, a peak external quantum efficiency (EQE) of 630%, fast rise/decay times of 0.35 ms/0.54 ms, a superior detectivity up to 1.35 × 1012 Jones and the capability to distinguish various waveforms and light intensities, the PDs present sensitive and persistent photoresponse underwater. As a result, proof-of-concept wireless transmission of ASCII codes in water is demonstrated.

A Flexible Self‐Powered UV Photodetector and Optical UV Filter Based on β‐Bi 2 O 3 /SnO 2 Quantum Dots Schottky Heterojunction

Abstract: Recently reported ultraviolet (UV) detectors majorly focus on exploration of photodetection properties like photon absorption and electron-hole pair generation to improve the photoresponsivity. However, UV sensors also have a potential advantage of monitoring the excessive UV exposure on skin. In this work, bismuth oxide/SnO2 quantum dots (QDs) vertical-junction-based self-powered UV photodetector and optical UV filter are demonstrated. β-Bi2O3 nanofibers are synthesized via electrospinning technique and SnO2 QDs are synthesized using a facile, single step hydrothermal process. Detailed morphological studies reveal the formation of 1D-Bi2O3 and 0D-SnO2. The fabricated self-powered Bi2O2/SnO2-based p–n heterojunction device exhibits a maximum responsivity of 62.5 µA W−1 and specific detectivity (D*) of 4.5 × 109 Jones attributing to the high absorption coefficient of β-Bi2O2 nanofibers and SnO2 QDs in the UV region. Further, the 1D β-Bi2O3 nanofibers and 0D SnO2 QDs are coated onto disposable cloth substrate to fabricate the UV optical filter which exhibits an exceptional ultraviolet protection factor of 159 and the photodetector device demonstrates high stability and reproducibility even after 1000 bending cycles. The strategy outlined here paves the way for development of bifunctional, cost-effective design and construction of wearable UV sensors and protective devices for advanced nano-electronic applications.