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Solution-processed upconversion photodetectors based on quantum dots
摘要： Upconversion photodetectors convert photons from the infrared to the visible light spectrum and are of use in applications such as infrared detection and imaging. High-performance upconversion devices are, however, typically based on vacuum-deposited materials, which are expensive and require high operating voltages, which limits their implementation in flexible systems. Here we report solution-processed optical upconversion photodetectors with a high photon-to-photon conversion efficiency of 6.5% and a low turn-on voltage of 2.5 V. Our devices consist of a colloidal lead sulfide quantum dot layer for harvesting infrared light that is monolithically coupled to a cadmium selenide/zinc selenide quantum dot layer for visible-light emission. We optimized the charge-extraction layers in these devices by incorporating silver nanoparticles into the electron transport layers to enable carrier tunnelling. Our photodetectors exhibit a low dark current, high detectivity (6.4 × 1012 Jones) and millisecond response time, and are compatible with flexible substrates. We also show that the devices can be used for in vitro bioimaging.
关键词： quantum dots,infrared detection,bioimaging,flexible electronics,upconversion photodetectors
更新于2025-09-23 15:21:01
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Mid-Wavelength Infrared Responsivity of Colloidal Quantum Dot/Organic Hybrid Photodetectors
摘要： Colloidal quantum dot/organic hybrid materials approach offer a path toward engineering solution-processed photodetectors with extended spectral responsivity in the infrared. We demonstrate this approach in the technologically important thermal infrared region of mid-wavelength infrared, utilizing a solution blend of Ag2Se colloidal quantum dots and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We report on the device fabrication and their room temperature optical, electrical, and optoelectronic properties. At room temperature, a responsivity of 0.2 mA/W was measured under 5 μm irradiation and 5 V bias. The new hybrid optoelectronic film demonstrated the advantage of cost-effectiveness and greater fabrication versatility than the single crystal or epitaxial semiconductors that comprise today’s infrared technologies.
关键词： Colloidal quantum dots,Photodetectors,Mid-wavelength infrared,Organic hybrid,Responsivity
更新于2025-09-23 15:21:01
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27 GHz Silicon-contacted waveguide-coupled Ge/Si avalanche photodiode
摘要： We report a silicon-contacted Ge/Si avalanche photodiode with RF gain of 11 and a bandwidth of 27 GHz at -12 V operating at 1310 nm. The device is fabricated in an established Si photonics platform without additional process complexity and contacts only on Si. Wafer-scale performance data are presented confirming the reproducibility and the manufacturability of the device. Wide open eye diagrams are for 25, 40 and 50 Gbps data-rates. The demonstration of such avalanche photodiode shows great potential for improving optical link margins for optical transceivers operating at 400 Gb/s and beyond.
关键词： Silicon Photonics,Optical Interconnection,Germanium,Photodetectors
更新于2025-09-23 15:21:01
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An Electrically Modulated Singlea??Color/Duala??Color Imaging Photodetector
摘要： An electrically modulated single-/dual-color imaging photodetector with fast response speed is developed based on a small molecule (COi8DFIC)/perovskite (CH3NH3PbBr3) hybrid film. Owing to the type-I heterojunction, the device can facilely transform dual-color images to single-color images by applying a small bias voltage. The photodetector exhibits two distinct cut-off wavelengths at ≈544 nm (visible region) and ≈920 nm (near-infrared region), respectively, without any power supply. Its two peak responsivities are 0.16 A W?1 at ≈525 nm and 0.041 A W?1 at ≈860 nm with a fast response speed (≈102 ns). Under 0.6 V bias, the photodetector can operate in a single-color mode with a peak responsivity of 0.09 A W?1 at ≈475 nm, showing a fast response speed (≈102 ns). A physical model based on band energy theory is developed to illustrate the origin of the tunable single-/dual-color photodetection. This work will stimulate new approaches for developing solution-processed multifunctional photodetectors for imaging photodetection in complex circumstances.
关键词： organic/perovskite photodetectors,response speed,dual-color imaging
更新于2025-09-23 15:21:01
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Mid-infrared dual-comb spectroscopy with room-temperature bi-functional interband cascade lasers and detectors
摘要： Interband cascade (IC) laser structures offer attractive potential for operation at room temperature as both broadband coherent sources of mid-infrared light and fast photodetectors. This makes the realization of extremely compact spectrometers on a monolithic platform possible, and even dual-comb spectroscopy (DCS) configurations. IC comb devices are perfect candidates for this configuration, since they develop near-THz-wide optical frequency comb spectra from a millimeter-sized cavity, using a multi-stage structure that can also function as a very fast photodetector. In this work, we leverage IC photodetectors with a gigahertz bandwidth to demonstrate a self-contained, free-running, room-temperature DCS system in the mid-infrared. The DCS system used detection by the same bi-functional IC device structure to measure 1,1-difluoroethane over (cid:2)600 GHz of optical coverage around 3.6 mm. These results show that the IC platform is suitable for full integration as a broadband, high-resolution on-chip spectrometer in a future chemical sensing system.
关键词： mid-infrared,photodetectors,dual-comb spectroscopy,interband cascade lasers,room-temperature
更新于2025-09-23 15:21:01
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Structural Design and Pyroelectric Property of SnS/CdS Heterojunctions Contrived for Low-Temperature Visible Photodetectors
摘要： The traditional photodetectors based on photoelectric effect exhibit inferior response or even out of operation with the decrease of temperature. However, cryogenic visible light detection is increasingly demanded in deep space and polar exploration. Herein, a self-powered visible photodetector coupling pyroelectricity and photoelectricity to optimize the cryogenic detecting performance is designed in which hydrothermally grown CdS nanorod array is covered by SnS nanoflakes. The choice of SnS allows the detector with strong visible light absorption and great photoelectric conversion efficiency, while the CdS nanorod structure with pyroelectricity can effectively modulate the behavior of photogenerated carriers at low temperatures. It is found that the response characteristics of the photodetector are dominated by the combination of pyroelectric and photoelectric effects, which becomes more significant with the reduced temperature. Specifically, at 130 K temperature, the photoresponse current under 650 nm light is improved by 7.5 times as that at room temperature, while the ratio of pyroelectric current to photocurrent can be increased to 400%. Meanwhile, the responsivity and detectivity are as high as 10.4 mA W?1 and 3.56 × 1011 Jones, respectively. This work provides a promising approach to develop high-performance self-powered visible photodetectors with low-temperature operating capability.
关键词： pyroelectric,CdS,photodetectors,self-powered,low temperature
更新于2025-09-23 15:21:01
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[IEEE 2019 Device Research Conference (DRC) - Ann Arbor, MI, USA (2019.6.23-2019.6.26)] 2019 Device Research Conference (DRC) - High-Responsivity Flexible Photodetectors based on MOVPE-MoS <sub/>2</sub>
摘要： We have presented flexible MSM photodetectors based on MOVPE-MoS2. These photosensing devices with high dynamic ranges up to 83dB and high responsivities of up to 550 A/W at low bias make this scalable approach a perfect candidate for future optical sensors in the medical field in which bendable electronics is highly desired. The MOVPE-MoS2 on wafer scale is also interesting for MoS2 FETs with high current on/off ratios of six orders of magnitude, fabricated with standard contact lithography enabling large-scale flexible electronic circuits.
关键词： 2D materials,MoS2,MOVPE,photodetectors,flexible electronics
更新于2025-09-23 15:21:01
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CMOS Nanophotonic Sensor with Integrated Readout System
摘要： The measurement of nanophotonic sensors currently requires the use of external measuring equipment for their read-out such as an optical spectrum analyzer, spectrophotometer, or detectors. This requirement of external laboratory-based measuring equipment creates a 'chip-in-a-lab' dilemma and hinders the use of nanophotonic sensors in practical applications. Making nanophotonic sensors usable in everyday life requires miniaturization of not only the sensor chip itself but also the equipment used for its measurement. In this paper, we have removed the need of external measuring equipment by monolithically integrating 1-D grating structures with a complementary metal-oxide-semiconductor (CMOS) integrated circuit having an array of photodiodes. By doing so, we get a direct electrical read-out of the refractive index changes induced when applying different analytes to grating structures. The gratings are made of CMOS compatible silicon nitride. Employing a nanophotonic sensor made of CMOS compatible material allows fabrication of the integrated sensor chip in a commercial CMOS foundry, enabling mass production for commercialization with low cost. Our results present a significant step toward transforming present laboratory-based nanophotonic sensors into practical portable devices to enable applications away from the analytical laboratory. We anticipate the work will have a major impact on technology for personalized medicine, environmental, and industrial sensing.
关键词： Diffraction gratings,nanophotonics,photodetectors,optoelectronics,sensors
更新于2025-09-23 15:21:01
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Optimizing the performance of ZnO/Au/MgZnO/SiO2 sandwich structured UV photodetectors by surface plasmons in Ag nanoparticles
摘要： The dual-wavelength UV photodetector (PD) with sandwich structure of ZnO/Au/MgZnO/SiO2 was fabricated and investigated with an emphasis on the effects of the Ag nanoparticles localized surface plasmons (LSPs). The results demonstrated that the modification in Ag nanoparticle (NP) position played a remarkable influence on the performance of dual-wavelength UV photodetectors. In comparison with decorating Ag NPs on the surface of the PDs, embedding Ag NPs between the MgZnO and ZnO films could improve two peak responsivities (caused by MgZnO and ZnO layers) significantly. By calculating the responsivities enhancement ratio of double layers (MgZnO and ZnO), the results indicated that the enhancement ratio of MgZnO is higher than that of ZnO. This was ascribed to LSPs of energy match with MgZnO which was superior to ZnO. This work described a creative method for increasing the performance of dual-wavelength UV PDs.
关键词： MgZnO,Ag nanoparticles,Dual wavelength,ZnO,Surface plasmons,UV photodetectors
更新于2025-09-23 15:21:01
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Effects of Size and Localized States in Charge Carrier Dynamics and Performance of Solution Processed Graphene Quantum Dots/Silicon Heterojunction near-UV Photodetectors
摘要： Influence of size and localized defect states on photogenerated carrier recombination dynamics, which affects the performance of graphene quantum dots (GQDs) based Si-compatible near-UV heterojunction photodetectors, is reported. GQDs of varying size from ~3.0 to ~8.0 nm have been prepared by a top down method of oxidative cutting of graphene oxide followed by hydrothermal reduction and gradient centrifugation at different speeds. Structural, compositional, photophysical characteristics and photocarrier dynamics of different sized samples have been studied. Spectroscopic features and carrier dynamics of GQDs are effectively controlled by their size and localized surface states, which also determine the average recombination lifetime of photo-generated carriers. Two-terminal vertical heterojunction photodetector devices fabricated using solution processed quantum dots exhibit superior performance over a broad spectrum with a peak response in the near UV (380 nm) region. The device fabricated using ~6.0 nm diameter GQDs displayed highest peak responsivity of 3.5 A/W showing an interesting correlation with carrier dynamics. To our best knowledge, this is the only report in graphene quantum dots or carbon nanostructure genre, showing the direct correlation between size of the quantum dots and localized surface states on photocarrier dynamics and consequential performance of photodetector devices.
关键词： Graphene quantum dots,carrier dynamics,heterojunction,Si-compatible,near-UV photodetectors
更新于2025-09-23 15:21:01