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n-ZnO/p-GaN heterojunction ultraviolet (UV) photo detectors with high responsivity and fast response time grown by chemical vapor deposition technique
摘要： High quality c-axis oriented n-type ZnO epitaxial films are grown on p-type c-GaN/sapphire templates using a chemical vapor deposition technique where metallic zinc is used as the Zn source. n-ZnO/p-GaN heterojunctions were thus formed and show rectifying behaviour with a turn-on voltage of ～2.4 V and a very low leakage current of 1 × 10?11 A. Study of the spectral distribution of the photo response properties of these heterostructures shows a maximum at a wavelength of 366 nm with a peak responsivity of ～0.4 mA/W at zero bias condition. The peak responsivity increases further with the applied forward bias and reaches ～191 mA/W at 1 V. The spectral profile shows a sharp reduction in responsivity for wavelengths larger than ≈400 nm, making these devices suitable for application in solar blind UV detection. These devices are also found to show a fast response with a rise/decay time of only a few milliseconds. The study also reveals that the photo-responsivity of these devices depends crucially on the microcrystalline quality of the ZnO layers.
关键词： UV detector,photoresponse,n-ZnO/p-GaN heterojunction,epitaxial films
更新于2025-09-23 15:21:01
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Squaramide-Based Pt(II) Complexes as Potential Oxygen-Regulated Light-Triggered Photocages
摘要： Two new squaramide-based platinum(II) complexes C1 and C2 have been synthesized and fully characterized. Their photoresponse has been assessed and is discussed. A remarkable enhancement in the DNA binding activity has been observed for both complexes, up on irradiation. For C2, the release of Pt(II) provoked by its irradiation has been studied. The response of C2 has been found to be regulated by the presence of oxygen. In vitro cytotoxicity tests show an enhancement in the activity of complex C2 after selective irradiation under hypoxic conditions. Resulting Pt(II) species have been isolated and characterized by various analytical methods establishing this type of squaramido-based complexes as a proof of concept for new Pt(II) photocages.
关键词： photocages,squaramide-based platinum(II) complexes,photoresponse,DNA binding activity,oxygen-regulated
更新于2025-09-23 15:21:01
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Carrier transport and recombination dynamics of InAs/GaAs sub-monolayer quantum dot near infrared photodetector
摘要： Here, we present a relative study of tunnel-induced photocarrier escape processes in a laterally coupled InAs sub-monolayer quantum dot-based photodetector (SML QD-PD) as a function of fractional coverage from 0.4 ML to 0.8 ML. Both by simulation and experiment, we have quantitatively described the temperature dependent interband photoresponse spectrally tuned in the near infrared region (835 nm–890 nm) on the basis of mutual competition between the interband carrier recombination and interdot tunneling lifetime with varying SML coverage. The progressively increasing recombination lifetime and decreasing interdot tunneling lifetime with increasing SML coverage has attributed to a faster photoresponse and greater responsivity. At higher coverage fraction, tunnel induced fast speed photocarrier transit through lateral array of SML QDs has been found to be capable of offering a faster temporal response (100 μs) with faithful reproducibility up to higher frequencies (1.3 KHz). Here, we report a powerful strategy to simultaneously tune responsivity, speed of time response and detectivity by externally controlling the SML coverage. This time response is measured to be nine times faster than a conventional SK QD photodetector. With increased coverage, inhibition of dark current due to trapping of injected charge carriers up to higher temperatures have resulted in high sustainable photodetectivity of 8 × 1011 cm Hz1/2 w?1 at ~250 K that offers near room temperature photodetection.
关键词： photoconductive gain,quantum dot photodetector,inter-dot tunneling,submonolayer coverage,near-infrared photoresponse,recombination dynamics,temporal photoresponse
更新于2025-09-23 15:19:57
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CdS core-Au/MXene-based photodetectors: Positive deep-UV photoresponse and negative UVa??Vis-NIR photoresponse
摘要： 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.
关键词： broader spectrum,positive photoresponse,negative photoresponse,photodetector,CdS core-Au
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Water Free Cleaning Solution: Environmental Durability of Electrodynamic Screen (EDS) Films in Water-Free Cleaning of Solar Collectors
摘要： We demonstrate the performance enhancement of field-effect transistor (FET)-based plasmonic terahertz (THz) detector with monolithic integrated antenna in low-impedance regime and report the experimental results of Si MOSFET impedance in THz regime using 0.2-THz measurement system. By designing FET with low-impedance ranges (<1 kΩ) and integrating antennas with impedances of 50 and 100 Ω, we found that our low-impedance MOSFETs have the input impedance criterion of 50 Ω at 0.2 THz and the MOSFETs with thinner gate oxide show the highly enhanced plasmonic photoresponses at 50-Ω antenna by 325 times from the result of the detector without antenna.
关键词： terahertz,impedance,photoresponse,MOSFET,detector,plasmonic
更新于2025-09-23 15:19:57
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Graphene-Nanowalls/Silicon Hybrid Heterojunction Photodetectors
摘要： We study and fabricate graphene nanowalls /silicon hybrid heterojunction photoconductive detector to provide process technology of the device and theoretical foundation for the purpose of preparation of high-performance photodetectors. The graphene nanowalls (GNWs) film is patterned by double-layered photoresist-based photolithography and reactive ion etching (RIE) process to achieve high quality GNWs channel and fabricate three different GNWs/Si heterojunction photoconductive detectors with n-doped, intrinsic and p-doped silicon substrates (n-Si, i-Si, p-Si), respectively. The GNWs film not only acts as a photoconductive channel for carrier transport, but also constructs a Schottky heterojunction with the silicon to participate in the separation and transport of photogenerated carriers. Since the injection of holes needs to pass through the Schottky junction region, the height of the Schottky barrier determines the injection ability of photogenerated carriers, which directly affects the photoconductive gain of the GNWs and silicon. In addition, under low bias VDS, the GNWs/n-Si photoresponse current is maximum and the GNWs/p-Si photoresponse current is minimum. The photoresponse is attributed to the barrier heights of the GNWs/n-Si, GNWs/i-Si, and GNWs/p-Si with values of 0.73 eV, 0.69 eV, and 0.63 eV, respectively. The higher the barrier, the more the number of photogenerated carriers injected into the GNWs will be, and the photoresponse current is large as well.
关键词： photoresponse,Schottky barrier,photoconductive,graphene nanowalls
更新于2025-09-23 15:19:57
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Polarization-Sensitive Self-Powered Type-II GeSe/MoS2 Van der Waals Heterojunction Photodetector
摘要： Polarization-sensitive photodetectors are highly desirable for high performance optical signal capture and stray light shielding in order to enhance the capability for detection and identification of targets in the dark, haze and other complex environments. Usually, filters and polarizers are utilized for conventional devices to achieve polarization-sensitive detection. Herein, to simplify the optical system, a 2-D self-powered polarization-sensitive photodetector is fabricated based on a stacked GeSe/MoS2 van der Waals (vdWs) heterojunction which facilitates efficient separation and transportation of the photogenerated carriers, due to type-II band alignment. Accordingly, a high performance self-powered photodetector is achieved with merits of a very large on-off ratio photocurrent at zero bias of currently 104 and a high responsivity (Rλ) of 105 mA/W with the external quantum efficiency (EQE) of 24.2%. Furthermore, a broad spectral photoresponse is extended from 380 nm to 1064 nm owing to the high absorption coefficient in a wide spectral region. One of the key benefits from these highly anisotropic orthorhombic structures of layered GeSe is self-powered polarization sensitive detection with a peak/valley ratio up to 2.95. This is realized irradiating with a 532 nm wavelength laser with which a maximum photoresponsivity of up to 590 mA/W is reached when the input polarization is parallel to the armchair direction. This work provides a facile route to fabricate self-powered polarization-sensitive photodetectors from GeSe/MoS2 vdW heterojunctions for integrated optoelectronic devices.
关键词： polarization sensitive photodetector,self-powered,type-II band alignment,GeSe/MoS2 heterojunction,broad spectral photoresponse
更新于2025-09-23 15:19:57
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Integrated Perovskite/Organic Photovoltaics with Ultrahigh Photocurrent and Photoresponse Approaching 1000a??nm
摘要： To enhance photoresponse of common-used perovskite materials in the near-infrared (NIR) region, a fused-ring electron acceptor (F8IC) with strong NIR absorption and high electron mobility was used to blend with a narrow-bandgap polymer donor (PTB7-Th) to construct organic bulk heterojunction (OBHJ), and this OBHJ was then integrated with the perovskite solar cells. The integrated perovskite/OBHJ solar cells exhibit strong photoresponse approaching 1000 nm and an ultrahigh short-circuit current density of 28.2 mA cm-2, which is much higher than the traditional perovskite solar cells and organic solar cells.
关键词： integrated solar cell,perovskite solar cell,ultrahigh photocurrent,NIR photoresponse,organic solar cell
更新于2025-09-23 15:19:57
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Structural and optoelectronic characterization of Cu2CoSnS4 quaternary functional photodetectors
摘要： Al/p-Si/Cu2CoSnS4/Al quaternary functional semiconductor photodetectors showing solar detector properties were produced via sol-gel method. SEM, EDS and XRD techniques were used in the confirmation of the chemical composition of the photodiodes where nanoparticle like characteristics of Cu2CoSnS4 was seen. UV-vis spectroscopy was used in the investigation of optoelectronic characteristics. It was seen that photodiodes have a high absorption rate with minimum reflectance, bandgap energy was calculated as 1.19 eV. Current – time and current – voltage characteristics of the photodiodes revealed that photodiodes are sensitive to daylight; photodiodes present rectifying characteristics. Thermionic emission theory was used in the calculation of barrier height, ideality factor, photoresponse, photosensitivity, and linear dynamic rate characteristics. Capacitance – voltage, conductance – voltage, corrective capacitance – voltage, corrective conductance – voltage graphs were used to investigate the electrical properties of the Al/p-Si/Cu2CoSnS4/Al photodiodes. The electrical characteristics of the photodiodes reflect frequency dependent characteristics. Such a behaviour was found to be an indication of the existence of interface states. The density of interface (Dit) calculations revealed that the density of interface states strongly depends on AC signal frequency where diminished Dit was seen for increased signal frequency.
关键词： photodetector,photoresponse,Cu2NiSnS4 photodiodes,quaternary functional photodiodes,solar detectors
更新于2025-09-23 15:19:57
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Three-dimensional Lead Iodide Perovskitoid Hybrids with High X-ray Photoresponse
摘要： Large organic A cations cannot stabilize the 3D perovskite AMX3 structure because they cannot be accommodated in the cubo-octhedral cage (do not follow the Goldschmidt tolerance factor rule), and they generally template low-dimensional structures. Here we report that the large di-cation aminomethylpyridinium (AMPY), can template novel 3D structures which resemble conventional perovskites. They have the formula (xAMPY)M2I6 (x = 3 or 4, M = Sn2+ or Pb2+) which is doubled the AMX3 formula. However, because of the steric requirement of the Goldschmidt tolerance factor rule, it is impossible for (xAMPY)M2I6 to form proper perovskite structures. Instead, a combination of corner-sharing and edge-sharing connectivity is adopted in these compounds leading to the new 3D structures. DFT calculations reveal that the compounds are indirect-bandgap semiconductors with direct bandgaps presenting at slightly higher energies and dispersive electronic bands. The bandgaps of the Sn and Pb compounds are ~ 1.7 eV and 2.0 eV, respectively, which is slightly higher than the corresponding AMI3 3D perovskites. The Raman spectra for the compounds are diffuse, with a broad rising central peak at very low frequencies around 0 cm-1, a feature that is characteristic of dynamical lattices, highly anharmonic, and dissipative vibrations very similar to the 3D AMX3 perovskites. Devices of (3AMPY)Pb2I6 crystals exhibit clear photoresponse under ambient light without applied bias, reflecting a high carrier mobility (μ) and long carrier lifetime (τ). The devices also exhibit sizable X-ray generated photocurrent with a high μτ product of ~1.2×10-4 cm2 /V and an X-ray sensitivity of 207 μC·Gy-1·cm-2.
关键词： Metal halide hybrids,mixed cations,photoresponse,X-ray detector,anomalous bandgap behavior
更新于2025-09-23 15:19:57