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Improvement of Photoresponse in Organic Phototransistors through Bulk Effect of Photoresponsive Gate Insulators
摘要： In this study, we investigate the bulk effect of photoresponsive gate insulators on the photoresponse of organic phototransistors (OPTs), using OPTs with poly(4-vinylphenol) layers of two different thicknesses. For the photoresponse, the interplay between the charge accumulation (capacitance) and light-absorbance capabilities of a photoresponsive gate insulator was investigated. Although an OPT with a thicker gate insulator exhibits a lower capacitance and hence a lower accumulation capability of photogenerating charges, a thicker poly(4-vinylphenol) layer, in contrast to a thinner one, absorbs more photons to generate more electron–hole pairs, resulting in a higher photoresponse of the device. That is, in these two cases, the degree of light absorption by the photoresponsive gate insulators dominantly governed the photoresponse of the device. Our physical description of the bulk effect of photoresponsive insulators on the performance of OPTs will provide a useful guideline for designing and constructing high-performance organic-based photosensing devices and systems.
关键词： polymer gate insulator,photoresponsive polymer,organic phototransistor,bulk effect,poly(4-vinylphenol)
更新于2025-09-19 17:13:59
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A 4H-SiC UV Phototransistor With Excellent Optical Gain Based on Controlled Potential Barrier
摘要： In this article, we report the experimental results of a visible-light-blind 4H-polytype silicon carbide phototransistor able to detect ultraviolet (UV) radiations for wavelengths lower than 380 nm with a significative improvement in the optical gain compared with the state-of-the-art of 4H-SiC UV phototransistors. From the electro-optical measurements, the device shows a dark current of 0.62 pA, an ON-/OFF-current ratio of seven orders of magnitude up to bias voltage of ?0.5 V, and an excellent optical gain of 1.14·105 at 300 nm, whereas it is only 2.6·10?3 at 400 nm demonstrating a good rejection of visible radiations. Besides having high optical gain, the phototransistor is also more sensitive than the conventional 4H-SiC UV detectors for wavelengths with low penetration depths, because its structure is designed to have the electric field up to the radiated surface where the photogenerated electron–hole pairs are efficiently swept up before recombination occurs. The operating principle of the detector is also investigated, and we experimentally proved that differently from the conventional 4H-SiC bipolar junction transistor phototransistor, it is based on the change in the potential barrier height, which controls the current flow, due to the variation in the Fermi levels when the electron–hole pairs are photogenerated. A comparison with the state-of-the-art of 4H-SiC UV phototransistors is reported.
关键词： 4H-SiC semiconductor device,phototransistor,potential barrier,ultraviolet (UV) detector,electro-optical characterization
更新于2025-09-12 10:27:22
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SnSe2 Quantum Dots: Facile Fabrication and Application in Highly Responsive UV-Detectors
摘要： Synthesizing quantum dots (QDs) using simple methods and utilizing them in optoelectronic devices are active areas of research. In this paper, we fabricated SnSe2 QDs via sonication and a laser ablation process. Deionized water was used as a solvent, and there were no organic chemicals introduced in the process. It was a facile and environmentally-friendly method. We demonstrated an ultraviolet (UV)-detector based on monolayer graphene and SnSe2 QDs. The photoresponsivity of the detector was up to 7.5 × 106 mAW?1, and the photoresponse time was ~0.31 s. The n–n heterostructures between monolayer graphene and SnSe2 QDs improved the light absorption and the transportation of photocarriers, which could greatly increase the photoresponsivity of the device.
关键词： UV-detector,phototransistor,SnSe2 quantum dots,graphene
更新于2025-09-12 10:27:22
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Polymer Optical Fiber-Based Respiratory Sensors: Various Designs and Implementations
摘要： This research discusses the polymer optical ?ber sensor for respiratory measurements. The infrared LED that produces light will propagate along the polymer optical ?ber which will be received by the phototransistor and the di?erential ampli?er. The output voltage in the form of an analog signal will be converted to a digital signal by the Arduino Uno microcontroller and displayed on the computer. The polymer optical ?ber sensor is installed on the corset using a variety of con?guration (straight, sinusoidal, and spiral), placed in the abdomen, and a variety of positions (abdomen, chest, and back) using only a spiral con?guration. While doing the inspiration, the stomach will be enlarged so that the optical ?ber sensor will have strain. The strain will cause loss of power, the resulting light intensities received by the phototransistor are reduced, and the output voltage on the computer decreases. The result shows that the highest voltage amplitudes were in the spiral con?guration placed in the abdominal position for slow respiration measurements with the highest range, sensitivity, and resolution which are 0.119 V, 0.238 V/s, and 0.004 s, respectively. The advantages of our work are emphasized on measurement system simplicity, low cost, easy fabrication, and handy operation and can be connected with the Arduino Uno microcontroller and computer.
关键词： phototransistor,respiratory sensor,differential ampli?er,Arduino Uno microcontroller,infrared LED,polymer optical ?ber
更新于2025-09-12 10:27:22
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Solution-Processed Phototransistors Combining Organic Absorber and Charge Transporting Oxide for Visible to Infrared Light Detection
摘要： This report demonstrates high-performance infrared phototransistors that uses a broadband absorbing organic bulk heterojunction (BHJ) layer responsive from the visible to the shortwave infrared, from 500 nm to 1400 nm. The device structure is based on a bilayer transistor channel that decouples charge photogeneration and transport, enabling independent optimization of each process. The organic BHJ layer is improved by incorporating camphor, a highly polarizable additive that increases carrier lifetime. An indium zinc oxide transport layer with high electron mobility is employed for rapid charge transport. As a result, the phototransistors achieve a dynamic range of 127 dB and reach a specific detectivity of 5×1012 Jones under low power illumination of 20 nW/cm2, outperforming commercial germanium photodiodes in the spectral range below 1300 nm. The photodetector metrics are measured with respect to the applied voltage, incident light power, and temporal bandwidth, demonstrating operation at the video-frame rate of 50 Hz. In particular, the frequency and light dependence of the phototransistor characteristics are analyzed to understand the change in photoconductive gain under different working conditions.
关键词： shortwave infrared,phototransistor,indium zinc oxide,bulk heterojunction,carrier lifetime,semiconducting polymer,camphor
更新于2025-09-11 14:15:04
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Photocurrent Characteristics of Zinc-Oxide Films Prepared by Using Sputtering and Spin-Coating Methods
摘要： The photocurrent characteristics of zinc-oxide (ZnO) thin-film transistors (TFTs) prepared using radio-frequency sputtering and spin-coating methods were investigated. Various characterization methods were used to compare the physical and the chemical properties of the sputtered and the spin-coated ZnO films. X-ray photoelectron spectroscopy was used to investigate the chemical composition and state of the ZnO films. The transmittance and the optical band gap were measured by using UV-vis spectrometry. The crystal structures of the prepared ZnO films were examined by using an X-ray diffractometer, and the surfaces of the films were investigated by using scanning electron microscopy. ZnO TFTs were prepared using both sputter and solution processes, both of which showed photocurrent characteristics when illuminated by light. The sputtered ZnO TFTs had a photoresponsivity of 3.08 mA/W under illumination with 405-nm light while the solution-processed ZnO TFTs had a photoresponsivity of 5.56 mA/W. This study provides useful information for the development of optoelectronics based on ZnO.
关键词： Phototransistor,Sputter,Thin film transistor,Solution process,Zinc Oxide
更新于2025-09-10 09:29:36
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Enhanced Detectivity and Suppressed Dark Current of Perovskite-InGaZnO Phototransistor via PCBM Interlayer
摘要： Hybrid phototransistors based on InGaZnO (IGZO) metal oxide thin film transistor (TFT) and photoabsorbing capping layer such as perovskite (MAPbI3) is a promising low-cost device for developing advanced X-ray and UV flat panel imager. However, it is found that the introduction of MAPbI3 inevitably damages the IGZO channel layer during fabrication, leading to deteriorated TFT characteristics such as off current rising and threshold voltage shift. Here, we report an effective approach for improving the performance of the perovskite-IGZO phototransistor by inserting a PCBM or PCBM:PMMA interlayer between the patterned MAPbI3 and the IGZO. The interlayer effectively prevents the IGZO from damaging by the perovskite fabrication process, while allowing efficient charge transfer for photo sensing. In this configuration, we have achieved a high detectivity (1.35 × 1012 Jones) perovskite-IGZO phototransistor with suppressed off-state drain current (~10 pA) in the dark. This work points out the importance of interface engineering for realizing higher performance and reliable heterogeneous phototransistors.
关键词： IGZO,interlayer,phototransistor,perovskite,photodetector
更新于2025-09-10 09:29:36
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Organic single-crystal phototransistor with unique wavelength-detection characteristics; 具有独特波长检测特性的有机单晶光电晶体管;
摘要： Organic phototransistors based on high-quality 2,8-dichloro-5,11-dihexyl-indolo[3,2-b]carbazo (CHICZ) single show the highest photoresponsivity of 3×103 A W?1, photosensitivity of 2×104 and the detectivity can achieve 8.4×1014 Jones. We also discovered good linear dependence of log(photosensitivity) versus the wavelength when the devices were illuminated with a series of same-intensity but different-wavelength lights. The organic phototransistors based on CHICZ single crystal have potential applications in wavelength-detection.
关键词： photo-responsivity,photosensitivity,wavelength-detection,organic phototransistor,single crystal
更新于2025-09-10 09:29:36
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Performance analysis of photoresistor and phototransistor for automotive’s halogen and xenon bulbs light output
摘要： Illumination of any light is measured using a different kind of calibrated equipment’s available in the market such as a goniometer, spectral radiometer, photometer, Lux meter and camera based systems which directly display the illumination of automotive headlights light distribution in the unit of lux, foot-candles, lumens/sq. ft. and Lambert etc., In this research, we dealt with evaluating the photo resistor or Light Dependent Resistor (LDR) and phototransistor whether it is useful for sensing light patterns of Automotive Halogen and Xenon bulbs. The experiments are conducted during night hours under complete dark space. We have used the headlamp setup available in TATA SUMO VICTA vehicle in the Indian market and conducted the experiments separately for Halogen and Xenon bulbs under low and high beam operations at various degrees and test points within ten meters of distance. Also, we have compared the light intensity of halogen and xenon bulbs to prove the highest light intensity between halogen and Xenon bulbs. After doing a rigorous test with these two sensors it is understood both are good to sensing beam pattern of automotive bulbs and even it is good if we use an array of sensors or a mixed combination of sensors for measuring illumination purposes under perfect calibrations.
关键词： automotive,light output,xenon bulbs,phototransistor,halogen bulbs,photoresistor
更新于2025-09-10 09:29:36
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Noise Analysis of Group IV Material-Based Heterojunction Phototransistor for Fiber-Optic Telecommunication Networks
摘要： This paper presents an analytical study of noise behavior and spectral responsivity of Ge1?xSnx alloy-based heterojunction phototransistors (HPTs) for different Sn compositions and base doping concentrations. The structure consists of n-Ge/p-Ge1?xSnx layers pseudomorphically grown on Si substrate via Ge virtual substrate, compatible with complementary metal-oxide-semiconductor technology. The high absorption coefficient of the alloy in base significantly improves signal-to-noise ratio in the high-frequency region, leading to efficient photodetection in the C- and L-bands of fiber-optic telecommunication window. A comparison is made between the theoretical findings for GeSn HPTs and the available data for currently employed group III–V compound-based HPTs, to examine if GeSn-based HPT can be a good alternative.
关键词： GeSn alloys,absorption coefficient,spectral responsivity,heterojunction phototransistor,signal-to-noise ratio
更新于2025-09-09 09:28:46