Broad Spectral Photodetectors Research Articles

Broad spectral photodetectors based on BiOCl@boronate polymer core-shell heterojunctions

BiOCl has been actively explored as a promising material for photodetectors (PDs), but inefficient charge separation and narrow response spectral range limit the further development of BiOCl-based PDs. Herein, we show that coating BiOCl with a boronate polymer (BP) shell may provide a simple route to overcome the above limitations. The migration of Bi3+ from BiOCl to BP changes the energy level and enhances the light absorption of BP shell. Violent coordination at the core–shell interface, as well as Bi3+ migration induces the generation of Bi3+-O·-Bi3+ defects. Also, BP shell can reduce the darkcurrent of BiOCl@BPs PDs. The optimized PD assembled with BiOCl@BP1.9 (the subscript represents the shell thickness) shows fast photoresponse (rise time: 32, decay time: 52 ms, respectively), high on/off ratio, and responsivity of 119.77 μA/W under 365 nm light at 15 V. Moreover, BiOCl@BP PDs exhibit a gradually broadened spectral response range with the increase of BP shell thickness and show much higher photodetection performances. For example, under 940 nm light stimulation, the optimized PD (BiOCl@BP20.1) exhibits a high responsivity of 22.18 μA/W, 28 times that of BP PD. Our findings may provide a guideline for the design of high-performance PDs based on the precise construction of polymer-inorganic heterostructures.

Enhancing Photodetectivity of Si/Perovskite Heterojunction-Based Broad Spectral Photodiodes by Introducing C60 Hole Blocking Layer

The applications of broad spectral photodetectors in the fields of biological imaging and environmental remote sensing have received considerable attention in the past decades. However, the specific photodetectivity representing the lowest optical signal that can be detected by a photodetector remains unsatisfactory. Here. we reported the unprecedent enhancement of specific photodetectivity of broad spectral photodiodes based on the heterojunction of p-Si/polyvinyl pyrrolidone (PVP)-modified perovskite by introducing fullerene (C60) as the hole blocking layer (HBL). The results showed that, by inserting a C60 HBL between the PVP-perovskite and the top electrode, the dark current is significantly reduced and strongly dependent on C60 thickness. The dark current reaches a minimum at C60 thickness of 10 nm, which is only roughly one-thirtieth of that without the C60 layer. At the optimized C60 thickness, the specific photodetectivity is enhanced about an order of magnitude due to significantly reduced dark current, while the photoresponsivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}$ </tex-math></inline-formula> ) only slightly reduced.

UV–Vis–NIR broad spectral photodetectors facilely fabricated with nonmetal plasmonic WO3−x nanosheets

Plasmonic metal nanostructures have been widely applied in photodetectors for the enhanced light response range and sensitivity. In contrast, photodetection based on surface plasmon effect of the emerging plasmonic nonmetals has not been investigated. Here, single nonmetal plasmonic WO3−x nanosheets were used as the sensing material for UV–Vis–NIR broad spectral photodetectors. The plasmonic WO3−x nanosheets were synthesized by solvothermal and follow-up thermal treatment in a hydrogen-containing atmosphere, which exhibited a localized surface plasmon resonance (LSPR) band centered at 899 nm with broad spectral absorption spanned from UV to NIR. Then photodetectors fabricated facilely by depositing Au electrodes on a film of WO3−x nanosheets showed sensitive response for the regulation of conductance through the plasmonic hot free charge carriers. The responsivity and detectivity were 52 mA/W and 1.46 × 108 Jones under an incident light with a wavelength of 980 nm with an ultralow bias of 0.01 V, and went up to 538 mA/W and 4.75 × 108 Jones under 0.1 V. The results demonstrate the great potential of nonmetal plasmonic materials for photodetection.

UV-vis-IR Broad Spectral Photodetectors Based on VO2-ZnO Nanocrystal Films.

As a narrow band semiconductor at room temperature and a metallic material above ∼68 °C, functional VO2 films are widely investigated for smart windows, whereas their potential for ultraviolet–visible–infrared (UV–vis–IR) broad spectral photodetectors has not been efficiently studied. In this report, photodetectors based on VO2–ZnO nanocrystal composite films were prepared by nanocrystal-mist (NC-mist) deposition. An enhanced photodetection switching ratio was achieved covering the ultraviolet to infrared wavelength. Due to the synergetic effect of nanosize, surface, phase transition, percolation threshold, and the band structure of the heterojunction, the transfer and transport of photogenerated carriers modulate the device performance. This study probes new chances of applying VO2-semiconductor-based nanocomposites for broad spectral photodetectors.

CdS core-Au/MXene-based photodetectors: Positive deep-UV photoresponse and negative UV–Vis-NIR photoresponse

Exploring photodetectors with higher responsitivity and broader spectral response is crucial for optoelectronic applications. Inverse photoresponse is discovered from photodetectors based on cadmium sulfide modified by Au (CdS core-Au). The devices are capable of detecting photons with a broader spectrum from deep-ultraviolet to near-infrared. Under the illumination of visible light at 405 nm, negative photoresponse with higher responsivity (86 mA/W) and larger specific detectivity (1.34 × 1011 Jones) are observed owing to the thermal mechanism. Upon deep-ultraviolet light illumination, the photodetectors exhibit positive photoresponse. These findings provide a new approach to broad spectral photodetectors and other inventive optoelectronic devices.

Defects induced broad spectral photoresponse of PVT-grown bulk AlN crystals

Aluminum nitride (AlN) is a wide bandgap semiconductor with promising application prospect in deep ultraviolet optoelectronic devices. Here, bulk AlN crystals in millimeter size were grown using an improved physical vapor transport technique. Schottky diodes based on these crystals demonstrated good photoresponse to a broad spectral range from 261 nm to 1064 nm. The photoresponse is attributed to the defects induced midgap energy states. The device demonstrated a photo responsivity up to 3.7 AW−1 at 360 nm with bias voltage of −10 V. This research paves a new way for broad spectral photodetectors.

Ultrasensitivity broadband photodetectors based on perovskite: Research on film crystallization and electrode optimization

Broad absorption bandwidth photodetectors based on organo-metal halide perovskite absorbers is an attractive means of resolving the narrow absorption of organic semiconductors. Here we report the achievement and characterization of broad spectral photodetectors based on CH3NH3PbI3−xClx, which has been optimized with four different electrodes and a specially modified highly crystallized active layer. This work use six different lasers which wavelength range from ∼405 nm to ∼808 nm as the illuminations, and shows clearly that the Au electrode devices have ultrahigh photosensitivity (P=IphIdark=Iill−IdarkIdark, up to 3.5 × 106 at incident light power of 38 mW/cm2) and such low dark current of ∼0.01 nA at −10 V. In addition, we achieved a relatively high photoresponsivity of 11.5 A/W at incident optical power ∼0.8 μW/cm2 for Ag electrode devices. Furthermore, this work demonstrates that the devices of Al electrode have an unexpected low performance, which has been proved to be caused by serious oxidization through XPS test results, this unpopularity may due to the roughness morphology at the interface and instability of Al chemical property. Our work will provide a strategy to fabricate facile and ultrasensitive broadband photodetectors with perovskite as absorber and several familiar metals as electrodes.

Design and construction of ultra-thin MoSe2 nanosheet-based heterojunction for high-speed and low-noise photodetection

Advances in the photocurrent conversion of two-dimensional (2D) transition metal dichalcogenides have enabled the realization and application of ultrasensitive and broad-spectral photodetectors. The requirements of previous devices constantly drive for complex technological implementation, resulting in limits in scale and complexity. Furthermore, the development of large-area and low-cost photodetectors would be beneficial for applications. Therefore, we demonstrate a novel design of a heterojunction photodetector based on solution-processed ultrathin MoSe2 nanosheets to satisfy the requirements of its application. The photodetector exhibits a high sensitivity to visible–near infrared light, with a linear dynamic range over 124 decibels (dB), a detectivity of ~1.2 × 1012 Jones, and noise current approaching 0.1 pA·Hz–1/2 at zero bias. Significantly, the device shows an ultra-high response speed up to 30 ns with a 3-dB predicted bandwidth over 32 MHz, which is far better than that of most of the 2D nanostructured and solution-processable photodetectors reported thus far and is comparable to that of commercial Si photodetectors. Combining our results with material-preparation methods, together with the methodology of device fabrication presented herein, can provide a pathway for the large-area integration of low-cost, high-speed photodetectors.

Quantum dots based broad spectral photodetectors with wavelength detecting ability

Board spectral photodetectors are required for varied scientific and industrial applications, yet the studies of such devices are limited. In this work a CdSe/ZnS quantum dots (QDs) based photodetector with broad spectral detecting ability was fabricated through a simple approach. Due to the discrete electronic states of QDs, the photodetector was more sensitive to incident wavelengths than incident power densities, and the photocurrent decreased monotonously with increasing incident wavelength, which could also realize the wavelength detection of incident light. This character provides a new way to achieve color or image sensing, and it could also broaden the photodetection and photosensing applications of QDs and semiconductor detectors.

Iron Pyrite (FeS2) Broad Spectral and Magnetically Responsive Photodetectors

Earth‐abundant iron pyrite (FeS2) nanocrystals show great potential in broad photosensing applications due to their high photoabsorption coefficient (&gt;105 cm−1) and ideal bandgap (0.95 eV). However, broad spectral photodetectors using the FeS2 nanojunctions and external stimuli‐driven photoresponse have not been demonstrated yet. Here, broad spectral FeS2/CdS bulk nanojunction photodetectors are demonstrated, covering the UV‐Vis‐NIR wavelength range. This is the first time shape‐dependent FeS2 nanocrystals and a dilute magnetic semiconductor phase exhibiting fast photoresponse time (10 ms) and high responsitivity (174.9 A/W) is demonstrated. Tunable photocurrent (73% change) is observed under the magnetic field effect due to the interdiffusion‐controlled diluted magnetic semiconductor CdFeS phase. The broad spectral FeS2‐based photodetectors open up a new tactic for solution‐processed next generation efficient and sustainable photosensing devices.