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High Sensitivity Visible-Near Infrared Organic Photodetector Based on Non-fullerene Acceptor
摘要： Highly sensitive solution-processed organic photodetectors (OPDs) with a broadband response ranging from visible to near infrared (NIR) and excellent overall device performance are demonstrated. The OPDs were fabricated from a blend consisting of a wide bandgap polymer donor and a newly developed fused octacylic small-molecule electron acceptor with acceptor–donor–acceptor structure, which shows relatively high and balanced hole/electron mobility and allow for thicker photoactive layer (~300 nm). In conjunction with the use of an optimized inverted device structure, the dark current density of the OPDs was suppressed to an ultralow level of (8.3±5.5)×10-10A cm-2 at bias of –1 V and the capability to directly weak light intensity is down to 0.24 pW cm?2, both are among the lowest reported values for OPDs. Owing to the low shot noise enabled by the inverted structure and the low thermal noise due to the high shunt resistance of the device, the obtained OPDs shows spectrally flat photoresponse in the range of 350–950 nm (UV-Vis-NIR) and a maximal specific detectivity (D*) of (2.1±0.1)×1013 Jones at 800–900 nm, which is among the best results of NIR OPDs reported to date and represents a highly sensitive photodetector for weak optical signal detection. Besides, the OPDs shows a wide bandwidth of 30 kHz, fast temporal response time around 12 us ~14 us and a large linear dynamic range of 106 dB.
关键词： dark current density,specific detectivity,non-fullerene acceptors,weak optical signal detection,organic photodetectors
更新于2025-09-23 15:19:57
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MSM-photodetector with ZnSe/ZnS/GaAs Bragg reflector
摘要： The effect of a ZnSe/ZnS/GaAs distributed Bragg reflector on the spectral response of a metal–semiconductor–metal (MSM)-diode is investigated. Good agreement is obtained between the calculated and experimental reflection spectra of the ZnSe/ZnS/GaAs heterostructure forming a distributed Bragg reflector in the MSM-diode. The MSM-detector provides a two-color response at 420 and 472 nm, a sharp decrease in photosensitivity in the long-wave part of the response signal, high quantum efficiency of 53%, and low dark current of 5 × 10?10 A. The two-color response of the detector can be adjusted to the desired wavelength by appropriately selecting the heterostructure parameters.
关键词： Metal–semiconductor–metal (MSM) diode,Dark current,Heterostructure,Infrared detectors,Bragg reflector,Spectral response
更新于2025-09-19 17:13:59
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Flexible solar blind Ga2O3 ultraviolet photodetectors with high responsivity and photo-to-dark current ratio
摘要： In this work, flexible solar blind Ga2O3 ultraviolet photodetectors with high responsivity and photo-to-dark current ratio are demonstrated. The Ga2O3 films are obtained by the RF magnetron sputtering method on flexible polyimide (PI) substrates and the results demonstrate that all the films grown under various temperatures are amorphous. When the incident light wavelength is less than 254 nm, the incident light is effectively absorbed by the Ga2O3 film. By controlling the growth temperature of the material, the responsivity and photo-to-dark current ratio of the corresponding metal-semiconductor-metal photodetectors are significantly improved. At growth temperature of 200 oC, the current under 254 nm illumination obtains 396 nA at voltage of 20 V (corresponding responsivity is 52.6 A/W), the photo-to-dark current ratio is more than 105, and the external quantum efficiency reaches 2.6×10 4 %, which is among the best reported Ga2O3 ultraviolet photodetectors including the devices on the rigid substrates. After the bending and fatigue tests, the flexible detectors have negligible performance degradation, showing excellent mechanical and electrical stability.
关键词： solar blind photodetector,responsivity,photo-to-dark current ratio,Ga2O3,flexible device
更新于2025-09-19 17:13:59
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Investigation of electrical values of low-efficiency dye-sensitized solar cells (DSSCs)
摘要： Indium-tin-oxide (ITO)/density (d)- titanium dioxide (TiO2)/nonporous (nonp)-TiO2 is a TiO2-based bilayer photoanode. These photoanodes coated for dye-sensitized solar cells (DSSCs) were with nonp-TiO2 surface and had very thick ITO layer. DSSCs were fabricated with these photoanodes. After their current density-voltage (J-V) were analyzed, ?t was seen that they were low efficiency and the shape of their J-V curve was linear line instead of rectangle. In this study, it was examined the relationship between the dark current (IDC), the series resistance (Rs) and the shunt resistance (Rsh) were examined for evaluating the fill factor (FF) of low-efficiency DSSCs because of the photoanodes with nonp-TiO2 surfaces and very thick ITO for contact layer. It was seen in the J-V graph of DSSCs which had low FF value due to their IDC and low Rsh. The J-V graph of low-efficiency DSSCs is linear due to their low Rsh and high Rs values. Moreover, the too thick ITO layer decreases the resistance of photoanodes; however, electrons in these photoanodes can not efficiently transferred to external circuit from ITO contact layer of DSSCs.
关键词： Fill factor,Linear,Nonporous,Back electron,Low-efficiency,Dark current,Cell resistance
更新于2025-09-19 17:13:59
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Enhancing Small-Molecule Organic Photodetector Performance for Reflectance-Mode Photoplethysmography Sensor Applications
摘要： Organic photodetector performance for enhancing the sensing abilities of an organic photoplethysmography sensor was investigated. Optimized organic photodetector with an anode interlayer and a cathode interlayer showed reverse dark current density of 22 nA cm-2 at ?2 V and the external quantum efficiency of 53.3% at 0 V. This organic photodetector was fabricated monolithically with an organic light emitting diode on a glass substrate to achieve a reflectance-mode photoplethysmography sensor, demonstrating the impact of organic photodetector device performance on the measured photoplethysmography signal for sensing applications. Furthermore, we estimated the optimal sensor design for circular geometry in terms of device area and distance between organic light emitting diode and organic photodetector to maximize the signal-noise ratio and lower the power consumption of organic photoplethysmography sensor devices. For most favorable photoplethysmography sensor design, signal strength of 130 mV with 600 μW power consumption was measured.
关键词： detectivity,Organic photodetector,OLED,Interlayer,dark current density,signal to noise ratio (SNR),PPG Sensor
更新于2025-09-19 17:13:59
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A facile method to synthesize two-dimensional CsPb2Br5 nano-/micro-sheets for high-performance solution-processed photodetectors
摘要： In this paper, a facile method to synthesize two-dimentional (2D) all-inorganic CsPb2Br5 nano-/micro-sheets at room temperature and their application as the active layer in solution-processed high-performance photodetectors are presented. The obtained CsPb2Br5 nano-/micro-sheets showed a photoluminescence emission peak at 522 nm with a narrow full-width-at-half-maximum of ~17 nm, showing its high color purity, and an absorption peak at 307 nm with a shoulder peak at 339 nm. Then, the obtained CsPb2Br5 nano-/micro-sheets were used as the active layer in photoconductive photodetector and a high specific detectivity of 1.0×1012 Jones with a photoresponsivity of 0.02 A/W and an ultra-low dark current of ~10-12 A under 16 μW/cm2 405 nm illumination were obtained from photoconductive photodetector Au/CsPb2Br5(85μm)/Au. Further, the physical mechanism for the enhanced performance is discussed. Therefore, it provides a new method to suppress dark current for high-performance CsPb2Br5 photodetectors.
关键词： Solution-processed,Low dark-current,CsPb2Br5 nano-/micro-sheets,Photodetector
更新于2025-09-16 10:30:52
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Type-II superlattice photodetectors versus HgCdTe photodiodes
摘要： The development of the HgCdTe alloy as the most important intrinsic semiconductor for infrared (IR) technology is well established and recognized. In spite of the achievements in material and device quality, the drawbacks still exist due to bulk and surface instability, lower yields and higher costs particularly in fabrication of long wavelength infrared arrays. The dif?culties with this material encouraged to research on other compounds to improve device performance. Since the ?rst paper published by Sakaki and Esaki in 1978 it is well known that InAs and GaSb constitute a nearly lattice-matched material system offering great ?exibility in the design of IR optoelectronic devices. After four decades, the III-V type-II superlattice (T2SL) detector technology is under strong development as a possible alternative to HgCdTe. The novel ideas coming in design of detectors have enhanced the position of T2SLs in IR materials detector technology. It appears that T2SLs are especially helpful in the design of unipolar barriers. In this paper fundamental physical properties of two material systems, HgCdTe and T2SLs, are compared together with their in?uence on detector performance: dark current density, RA product, quantum ef?ciency, and noise equivalent different temperature. In comparison with HgCdTe, fundamental properties of T2SLs are inferior. On the other hand, T2SL and barrier detectors have several advantages to include lower tunnelling and surface leakage currents, and suppressed Auger recombination mechanism. Up to date, the promise of superior performance of these detectors has not been realized yet. In the paper we present that the performance of T2SL detectors (dark current, current responsivity, and noise equivalent difference temperature) is lower than bulk HgCdTe photodiodes. Due to stronger, less ionic chemical bonding of III-V semiconductors, these materials are attractive due to manufacturability and stability. It is also predicted that the interband T2SL quantum cascade devices will outperform the performance of the high operating temperature HgCdTe detectors.
关键词： Type-II superlattices,Responsivity,HgCdTe,Operability,Dark current,Interband cascade infrared detectors,Carrier lifetime
更新于2025-09-16 10:30:52
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The Effect of Inductively Coupled Plasma Etching on the I–V Curves of the APD with GaN/AlN Periodically‐Stacked‐STRUCTURE
摘要： Inductively Coupled Plasma (ICP) is widely used in dry etching of III-nitride materials, wherein the etching parameters of GaN and AlN are very different. In this paper, the ICP dry etching process parameters of GaN/AlN periodically-stacked-structure (PSS) for avalanche photodiode fabrication have been intensively studied and optimized. The flow rate ratio of Cl2/BCl3/Ar plasma, bias voltage, and the GaN-to-SiNx selectivity of ICP etching were optimized to achieve excellent surface morphology and nearly vertical sidewalls. It was found that the etching rate and the etched surface roughness of GaN/AlN material were significantly influenced by the flow rate of Cl2. After optimizing the etching procedure, the root-mean-square roughness (RMS) of the etched surface was measured to be 1.46 nm, which is close to the as grown surface. By employing the optimized ICP dry etching in the fabrication of the GaN/AlN PSS avalanche photodiode (APD), the dark current was suppressed from 3.6 A/cm2 to 8.2×10-3 A/cm2 at -90 V.
关键词： GaN/AlN,dark current,molecular beam epitaxy,inductively coupled plasma,avalanche photodiode
更新于2025-09-12 10:27:22
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Organic Photodetectors and their Application in Large Area and Flexible Image Sensors: The Role of Dark Current
摘要： Organic photodetectors (OPDs) have gained increasing interest as they offer cost-effective fabrication methods using low temperature processes, making them particularly attractive for large area image detectors on lightweight flexible plastic substrates. Moreover, their photophysical and optoelectronic properties can be tuned both at a material and device level. Visible-light OPDs are proposed for use in indirect-conversion X-ray detectors, fingerprint scanners, and intelligent surfaces for gesture recognition. Near-infrared OPDs find applications in biomedical imaging and optical communications. For most applications, minimizing the OPD dark current density (Jd) is crucial to improve important figures of merits such as the signal-to-noise ratio, the linear dynamic range, and the specific detectivity (D*). Here, a quantitative analysis of the intrinsic dark current processes shows that charge injection from the electrodes is the dominant contribution to Jd in OPDs. Jd reduction is typically addressed by fine-tuning the active layer energetics and stratification or by using charge blocking layers. Yet, most experimental Jd values are higher than the calculated intrinsic limit. Possible reasons for this deviation are discussed, including extrinsic defects in the photoactive layer and the presence of trap states. This provides the reader with guidelines to improve the OPD performances in view of imaging applications.
关键词： large area image sensors,charge injection,trap states,dark current,flexible image sensors,organic photodetectors
更新于2025-09-12 10:27:22
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An Amateur's Guide to Observing and Imaging the Heavens || Imaging with Cooled CCD Cameras
摘要： The latest DSLR cameras can do a very good job of astro-imaging and can, of course, be used for general photography as well, so why go to the expense of buying a cooled CCD camera? The main reason lies in the word ‘cooled’. All imaging chips produce dark current noise which increases with exposure time and is also highly dependent on its temperature, that of a typical chip dropping by half for each drop of 6 degrees Celsius in temperature. So, if the chip is cooled by 30 degrees below ambient temperature, the dark current noise will have dropped by about 5 times, so allowing longer exposures to be taken before dark current noise becomes a problem. Given dark skies that do not suffer from light pollution, this can allow images to reveal faint nebulosity that would otherwise be lost in the noise. When significant light pollution is present, the exposure times, and hence the dark current contribution, have to be less, before the skylight becomes obtrusive, and so cooling does not confer as great an advantage. The latest chips have very low dark currents, and it is rarely worth cooling them down below about –20 C. This temperature can normally be reached with the single-stage Peltier cooling employed in CCD cameras aimed at the amateur market.
关键词： Peltier cooling,light pollution,cooled CCD cameras,dark current noise,astro-imaging
更新于2025-09-12 10:27:22