Visible-blind Ultraviolet Photodetector Research Articles

Self-powered visible-blind ultraviolet photodetectors based on SnO2 nanowire cotton synthesized using thermal chemical vapor deposition

Self-powered visible-blind ultraviolet photodetectors based on SnO2 nanowire cotton synthesized using thermal chemical vapor deposition

P-NiO/n-ZnO heterojunctions for visible-blind UV and IR photodetectors: A low-temperature fabrication approach

We investigate the design and characterization of stacked semiconductor structures, specifically p-NiO on n-ZnO, for achieving a multispectral photo-response. This device is fabricated by depositing a thin film of NiO on ZnO using a simple, low-temperature spray pyrolysis technique. The resulting heterojunction device, formed on a glass substrate at 250 °C and annealed at 500 °C, exhibits visible-blind characteristics and demonstrates remarkable stability for ultraviolet (UV) and infrared (IR) detection with a low dark current of 22 nA. The Ag/p-NiO/n-ZnO/Ag device shows enhanced photo-response only at wavelengths of 253 nm and 900 nm with a quick response time (Tr = 4.6 ms and Td = 20.3 ms). The observed photo-current is attributed to defect-mediated charge transport at the interface. These promising results highlight the potential of p-NiO/n-ZnO heterojunction-based device for applications demanding robust performance as visible blind IR and UV photodetectors.

Epitaxial Growth of the Large-Scale, Highly-Ordered 3D GaN-Truncated Pyramid Array Toward an Ultrahigh Rejection Ratio and Responsivity Visible-Blind Ultraviolet Photodetection.

The micro- and nanostructures of III-nitride semiconductors captivate strong interest owing to their distinctive properties and myriad potential applications. Nevertheless, challenges endure in managing the damage inflicted on crystals through top-down processes or achieving extensive control over the large-area growth of these microstructures via bottom-up methods, thereby impacting their optical and electronic properties. Here, we present novel epitaxially grown 3D GaN truncated pyramid arrays (TPAs) on patterned Si substrates, devoid of any catalyst. These GaN TPAs feature highly ordered, large-scale structures, attributed to the utilization of 3D Si substrates and thin AlN interlayers to alleviate epitaxial strains and limit dislocation formation. Comprehensive characterization via scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and cathodoluminescence attests to the superior structural and optical attributes of these crystals. Furthermore, photoluminescence and ultraviolet (UV)-visible diffuse reflectance spectroscopy reveal sharp band-edge emission and significant light trapping in the UV bands. Employing these GaN TPAs, we constructed metal-semiconductor-metal visible-blind UV photodetectors (PDs) incorporating Ti3C2 MXene as Schottky electrodes. These PDs display exceptional responsivity, achieving 5.32 × 103 mA/W at 255 nm and an ultrahigh UV/visible rejection ratio (R255nm/R450nm) approaching 106, which are 1-2 orders of magnitude higher than most recently reported works. This exploration showcases novel GaN-based microstructures characterized by uniformity, ordered geometry, and exemplary crystalline integrity, paving the way for developing optoelectronic applications.

Self-Powered Visible-Blind Ultraviolet Photodetector Based on Organic-Inorganic Hybrid Copper Halide [N(C2H5)4]2[Cu2Br4

Organic-inorganic hybrid ternary copper halides offer a broader spectrum of structural possibilities for finely tuning their optoelectronic properties. Herein, we demonstrate for the first time the potential of [N(C2H5)4]2[Cu2Br4], a zero-dimensional hybrid copper halide [(TEA)2Cu2Br4], for ultraviolet (UV) photodetection. A self-powered, visible-blind UV photodetector based on a (TEA)2Cu2Br4/GaN heterojunction architecture is developed, exhibiting a high responsivity, a high detectivity, and fast response speeds. The device demonstrates exceptional stability against environmental oxygen/moisture, heat, and UV light illumination, surpassing the stability of reported copper-based UV photodetectors. Our work highlights the significant potential of (TEA)2Cu2Br4 as a lead-free, stable, and efficient material for next-generation UV photodetection technology.

Electrospun vanadium oxide hollow nanofibers based supercapacitor inspired triboelectric nanogenerator as self-powered visible-blind ultraviolet photodetector

Self-powered visible-blind ultraviolet (UV) photodetectors have emerged as sustainable alternatives in various sectors, including security, surveillance, and environmental monitoring. So, we report a vanadium oxide (V2O5) hollow nanofibers-based supercapacitor-inspired triboelectric nanogenerator (STENG) as a self-powered visible-blind UV photodetector. A novel designed STENG is fabricated using electrospun V2O5 hollow nanofibers-based coated on indium tin oxide coated polyethylene terephthalate sheet (ITO/PET) on top side and a layer of polyvinyl alcohol (PVA) & sulphuric acid over multi-walled carbon nanotubes (MWCNT) coated graphite sheet on bottom side. The optimized STENG demonstrates 34 V peak-to-peak open circuit voltage (Voc) and 2 μA of peak-to-peak short circuit current (Isc) by applying force via finger tapping. However, STENG's performance improves significantly to deliver 280 V Voc (peak-to-peak), and 6 μA Isc (peak-to-peak) with 0.49 W/m2 power density at 100 MΩ load resistance due to electrochemical charging. The output voltage of the STENG increases by 400 % under UV light, which refers to the excellent performance of STENG as a self-powered visible-blind UV photodetector with 266 V/W responsivity at 2.5 mW/cm2 intensity. Hence, the as-fabricated V2O5 hollow nanofibers-based STENG not only paves the way to fabricate a high-performance energy harvester, but can also be used as a self-powered UV-photodetector.

The enhanced responsivity and response speed of SnO2 visible-blind transparent photodetectors via the SiO2 passivation layer.

Recently, transparent ultraviolet (UV) photodetectors have gained wide attention for their giant potential in integrated transparent electronics applications. SnO2 films as a common candidate for visible-blind transparent ultraviolet photodetectors have attracted increasing attention. In this work, high-performance visible-blind transparent UV photodetectors based on SnO2 thin film and a SiO2 passivation layer were successfully synthesized by the sol-gel spin coating method for the first time. The obtained SnO2/SiO2 hybrid device has a transmittance of nearly 80% in the visible band at 400-700 nm and demonstrates a high responsivity of 769 mA W-1 and a detection sensitivity of 1.24 × 1014 Jones under UV light illumination. The UV-C/UV-A rejection ratio is greater than 106, indicating that the device has good photo-selectivity. In addition, after the introdution of the SiO2 layer, the response speed is 2 times higher than that of pure SnO2. The presence of the SiO2 layer reduces the exposed area of SnO2, passivates the oxygen vacancies on the surface of SnO2 and inhibits the surface chemical adsorption. The above results provide a new perspective for improving the performance of SnO2 thin film for visible-blind transparent ultraviolet photodetectors.

Conductance modification of molybdenum oxide thin films through oxygen-vacancy engineering for visible-blind ultraviolet photodetection

We propose a simple approach to locally modify the conductance of molybdenum oxide thin films with thermal annealing in oxygen atmosphere at relatively low temperature for constructing a visible-blind ultraviolet photoconductor. The amorphous MoO x is grown by remote plasma enhanced atomic layer deposition (RPALD), and then crystallized into α-MoO x at 500 °C in argon atmosphere, which exhibits good conductance with resistivity of 3.9 × 10−3 Ω cm due to the formation of oxygen vacancies. Good ohmic contact between Ti and the crystallized MoO x is demonstrated with specific contact resistance of 9.74 × 10−4 Ω cm2. The lateral Au/Ti-MoO x -Ti/Au structures are defined and the conductance of the exposed MoO x channel is significantly modified by thermal annealing in oxygen atmosphere to form a photodetector, which shows obvious photoresponse at the wavelength of less than 372 nm with low dark current of 0.9 pA at 5 V, and the remarkable responsivity of 0.75 mA W−1 at 280 nm is achieved with a high ultravoilet/visible rejection ratio. The low dark current and incredible responsivity can be attributed to the good ohmic contacts of untreated MoO x and the reduction of number of oxygen vacancies in the MoO x channel. The key role of oxygen vacancy on the conductance of MoO x has been demonstrated. Those results suggest that the MoO x thin films are promising candidate for visible-blind ultraviolet photodetectors in a simple complementary metal oxide semiconductor (CMOS)-compatible process.

Achieving High-Performance Self-Powered Visible-Blind Ultraviolet Photodetection Using Alloy Engineering.

The exploration and development of self-powered visible-blind ultraviolet photodetectors (VBUV PDs) with high responsivity and wavelength selectivity have far-reaching significance for versatile applications. Although In2O3 shows potential for UV detection due to good UV absorption and electrical transport properties, the poor wavelength selectivity impedes further application in VBUV PDs. Here, a self-powered photoelectrochemical-type (PEC) VBUV PD is demonstrated by using gallium-indium oxide alloys (Ga-In OAs). The self-powered Ga-In OAs-based PEC VBUV PDs exhibit good VBUV photodetection performance, including a high responsivity of 50.04 mA/W and a high detectivity of 6.03 × 1010 Jones under 254 nm light irradiation, a good wavelength selectivity (UV/visible light rejection ratio of 262.45), and a fast response time (0.45/0.38 s). The good self-powered VBUV detection performance of Ga-In OAs is attributed to the larger band gap and smaller charge-transfer resistance induced by alloy engineering, which not only suppresses the absorption of visible light but also accelerates interfacial charge transfer. Moreover, an underwater optical communication system is demonstrated by using the self-powered Ga-In OAs PEC VBUV PDs. This study demonstrates that alloy engineering is a powerful tool to improve the performance of In2O3-based PEC PDs, and Ga-In OAs have great application potential for underwater optoelectronic devices.

Spherulitic Crystallization of CsCu2I3 for High Performance Ultraviolet Photodetectors.

Ternary copper halides have become promising materials for UV photodetection due to their stability and eco-friendliness. However, the uncontrollable crystallization induces high-concentration defects in these films, inherently limiting further improvement in device performance. Herein, we reveal the antisolvent-assisted crystallization kinetics mechanism of CsCu2I3 during the film-forming process. The nucleation rate is manipulated by adjusting precursor supersaturation using different antisolvents, resulting in decreased density and preferential orientation of the nuclei within the wet film. Subsequent annealing leads to a homogeneous and low-defect CsCu2I3 film with 40-μm-scale spherulites. A resulting visible-blind ultraviolet photodetector exhibits a responsivity of 8.73 A W-1, a specific detectivity of 5.28 × 1012 jones, and a response speed of 1.12 ms. The unencapsulated photodetector shows negligible degradation of responsivity in ambient air (∼70% humidity) for one month. Moreover, the flexible device with a responsivity of 420.2 mA W-1 and a detectivity of 1.18 × 1012 jones also shows excellent bending stability.

Ultrafast self-powered visible blind UV photodetectors based on MgZnO vertical Schottky junction in crossbar geometry

In order to achieve ultrafast response in MgZnO based self-powered Schottky type photodetectors, it is crucial to decrease both the junction capacitance and carrier transit time. To meet these criteria, Au/MgZnO/ITO Schottky junction photodetectors have been realised in crossbar pattern, wherein the thickness of the MgZnO thin film deposited on patterned ITO-glass substrate is ∼ 200 nm and the cross-sectional area of the devices is 0.032 mm2. The semi-transparent 10 nm Au electrode on top of the MgZnO film serves as the Schottky electrode through which light enters the devices. The vertical geometry of the crossbar pattern and the associated small device cross-section results in a low junction capacitance of the devices of ∼ 27 pF at zero bias, which in turn produces very fast visible blind self-powered ultraviolet (UV) photoresponse with both the rise and fall times of ∼ 1.5 μs, that is hitherto unreported for MgZnO based Schottky junction photodetectors. The devices also demonstrate a peak responsivity of ∼ 49 mA/W at ∼ 280 nm with a cut-off wavelength of 336 nm. These Au/MgZnO/ITO Schottky photodetectors in crossbar pattern, with optimized device area, could be useful in applications requiring fast response, such as UV communication and UV imaging.

Highly Efficient Visible-Blind Ultraviolet Photodetector Based on Scalably Produced Titanium Dioxide Nanowire Arrays.

Here, we report a novel, feasible, and cost-effective method for the preparation of one-dimensional TiO2 nanowire arrays using a super-aligned carbon nanotube film as a template. Pure-anatase-phase TiO2 nanowires were scalably prepared in a suspended manner, and a high-performance ultraviolet (UV) photodetector was realized on a flexible substrate. The large surface area and one-dimensional nanostructure of the TiO2 nanowire array led to a high detectivity (1.35 × 1016 Jones) and an ultrahigh photo gain (2.6 × 104), respectively. A high photoresponsivity of 7.7 × 103 A/W was achieved under 7 μW/cm2 UV (λ = 365 nm) illumination at a 10 V bias voltage, which is much higher than those of commercial UV photodetectors. Additionally, by taking advantage of its anisotropic geometry, we found the TiO2 nanowire array showed polarized photodetection. The concept of using nanomaterial systems shows the potential for realization of nanostructured photodetectors for practical applications.

Fabrication of High-Performance Visible-Blind Ultraviolet Photodetectors Using Electro-ionic Conducting Supramolecular Nanofibers.

The detection of ultraviolet (UV) light is vital for various applications, such as chemical-biological analysis, communications, astronomical studies, and also for its adverse effects on human health. Organic UV photodetectors are gaining much attention in this scenario because they possess properties such as high spectral selectivity and mechanical flexibility. However, the achieved performance parameters are much more inferior than the inorganic counterparts because of the lower mobility of charge carriers in organic systems. Here, we report the fabrication of a high-performance visible-blind UV photodetector, using 1D supramolecular nanofibers. The nanofibers are visibly inactive and exhibit highly responsive behavior mainly for UV wavelengths (275-375 nm), the highest response being at ∼275 nm. The fabricated photodetectors demonstrate desired features, such as high responsivity and detectivity, high selectivity, low power consumption, and good mechanical flexibility, because of their unique electro-ionic behavior and 1D structure. The device performance is shown to be improved by several orders through the tweaking of both electronic and ionic conduction pathways while optimizing the electrode material, external humidity, applied voltage bias, and by introducing additional ions. We have achieved optimum responsivity and detectivity values of around 6265 A W-1 and 1.54 × 1014 Jones, respectively, which stand out compared with the previous organic UV photodetector reports. The present nanofiber system has great potential for integration in future generations of electronic gadgets.

Ultrathin In2 O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection.

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In2 O3 ) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In2 O3 NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36mA W-1 and a high specific detectivity of 4.43 × 1011 Jones under 254nm irradiation, which originates from the smaller charge transfer resistance (Rct ) at the In2 O3 NSs/electrolyte interface. The light absorption of In2 O3 NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In2 O3 NSs PEC PDs is 1567, which is 30 times higher than that of In2 O3 nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In2 O3 NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In2 O3 NSs have potential in underwater optoelectronic devices.

A self-powered, visible-blind ultraviolet photodetector based on ZnO nanorods/ZnS core–shell​ structure

In this paper, ZnO nanorods (NRs)/ZnS core–shell structure was prepared by the hydrothermal method to construct a self-powered, visible-blind ultraviolet (UV) photodetector. After covered by ZnS shell, the light absorption edge of ZnO NRs blue-shifts, which is positive for UV photodetection. Under UV illumination, ZnO NRs/ZnS-based photodetector with the shell thickness about 10 nm shows an obvious self-powered characteristics and its photocurrent is greatly enhanced compared with that of ZnO NRs-based device. The favorable energy band alignment is contributed to enhance the charge transfer ability and thus the photocurrent. Moreover, the photodetector shows a relatively high UV-visible responsivity ratio and detectivity (1.62 × 1012 Jones) under UV illumination.

Orientation Regulation of One-Dimensional CsCu2I3 Perovskites for Visible-Blind Ultraviolet Photodetectors.

Ternary copper halides with a formula of CsCu2X3 (X = Cl, Br, I) have been considered as prospective materials for ultraviolet (UV) photodetectors, due to their suitable band gaps, environmental stability, eco-friendliness, and low cost. However, the crystal orientation of one-dimensional (1D) CsCu2X3 perovskites significantly affects the exciton/carrier transport in the films and thus the photodetector performance. Here, we tune the crystal orientation and exciton/charge transport of 1D CsCu2I3 perovskite films by using antisolvents during the film formation process. Compared to the randomly oriented film treated by ethyl acetate, the CsCu2I3 film using toluene as antisolvent exhibits preferential (221)-oriented growth, which induces enhanced vertical exciton diffusion/charge transport and suppressed nonradiative recombination. On the basis of this strategy, we demonstrate a self-powered, stable, and visible-blind UV photodetector with significantly enhanced response speed and detectivity. Our work clarifies that tuning the crystal orientation of 1D CsCu2X3 perovskites is the key to achieve efficient exciton diffusion/charge transport and thus high-performance lead-free perovskite optoelectronic devices.

Hybrid visible-blind ultraviolet photodetector based on NiO thin-film phototransistor and p-NiO/n-Si heterojunction diode

A hybrid visible-blind ultraviolet (UV) photodetector, which combines a p-NiO/n-Si heterojunction diode and NiO-based thin-film phototransistor, was proposed, and its optoelectronic properties were studied. The hybrid photodetector exhibited a high quantum efficiency and photocurrent gain. The p-NiO/n-Si heterojunction separates the photogenerated electron–hole pairs, thereby reducing the recombination probability of the electron–hole pairs and enhancing photocurrent gain. In the hybrid photodetector, the ratio of the photo current to dark current (IP/ID) increased with an increase in the drain source voltage (VDS) because more photogenerated holes were extracted. Responsivity decreased with increasing positive gate voltage (VG) owing to the depleted channel layer. Conversely, the responsivity increases with increasing negative VG because more holes are accumulated at the surface of the NiO channel layer. The UV (280 nm)/visible (500 nm) rejection ratio is as high as 700–850, indicating that the prepared hybrid device is a good visible-blind photodetector. Detectivity increased from 6.72 × 1012 to 2.23 × 1013 Jones by decreasing VG from 10 to −10 V. Band diagrams of p-NiO/n-Si heterojunction diodes and NiO-based thin-film phototransistors were proposed to elucidate the mechanism of the photocurrent gain in the prepared hybrid photodetector.

A Self-Powered, Visible-Blind Ultraviolet Photodetector Based on Zno Nanorods/Zns Core-Shell Structure

A Self-Powered, Visible-Blind Ultraviolet Photodetector Based on Zno Nanorods/Zns Core-Shell Structure

High-performance self-powered visible-blind ultraviolet photodetection achieved by ferroelectric PbZr0.52Ti0.48O3 thin films

Self-powered visible-blind ultraviolet (UV) photodetection has been generally achieved based on the built-in electric field formed within the complicated devices such as pn or Schottky junctions, which involves a complicated device fabrication process. In contrast, employing the ferroelectric materials featured with unique bulk photovoltaic effect as absorbers will simplify the device structure and the subsequent device fabrication process without losing the performance of self-powered photodetection. In the current work, the fabrication of high-performance self-powered visible-blind UV photodetectors based on ferroelectric PbZr0.52Ti0.48O3 (PZT) thin films has been reported. The results showed that the spin-coated PZT thin films exhibited superior ferroelectric properties. On this basis, an efficient, stable, and repeatable self-powered UV photodetection has been achieved in the Au/PZT/FTO (fluorine-doped tin oxide) structured devices with the responsivity and detectivity as high as 0.092 A/W and 1.2 × 1012 Jones, respectively. More interestingly, the self-powered photocurrent has been further enhanced when downward polarizing the PZT thin film. The results reported in this work highlight the superiorities of ferroelectric PZT-based self-powered visible-blind UV photodetectors and provide valuable strategies for the fabrication of high-performance self-powered photodetectors with a simplified device structure in the future.

Self-powered UV photodetectors based on CsPbCl3 nanowires enabled by the synergistic effect of acetate and lanthanide ion passivation

Recently, photodetectors based on perovskite nanomaterials have attracted considerable attention in the visible spectral region owing to their large absorption coefficients, long diffusion lengths and high optical gains. However, the fabrication of self-powered visible-blind ultraviolet (UV) photodetectors is still challenging for the perovskite nanomaterials. This work developed the self-powered UV photodetector based on the Eu(AcO)3 promoted CsPbCl3 nanowires (NWs), enabled by the great separation efficiency of electron-hole pairs and high electron mobility of the one-dimentional (1D) morphology of perovskite materials. The perovskite CsPbCl3 NWs were synthesized by a modified hot-injection method with assistant of Eu(AcO)3 additive. As supported by the experimental investigations and DFT calculations, the adsorption of Eu3+ and AcO− ions to the surface of perovskite not only promotes the anisotropic growth of perovskite in (200) orientation, but also efficently passivates the halide defect of the perovskite nanomaterials. Moreover, the self-powered UV photodetector based on the Eu(AcO)3 promoted CsPbCl3 NWs displays a high responsivity of 398 mA W−1, detectivity up to 3.3 × 1011 Jones and fast response speed (24 ms) at 360 nm without external bias. The responsivity and detectivity of the device based on CsPbCl3 NWs are improved 8 and 205 times, comparing with the device based on bare CsPbCl3 NCs without passivation, respectively. In addition, the detectivity is comparable to some previous reports about perovskite NC-based UV photodetectors with additional bias. Our findings demonstrate the promising potential of 1D perovskite NWs for developing the next-generation self-powered UV photodetectors.

Heteroepitaxial growth of high Mg-content single-phased W-MgZnO on ZnO matrixes in various nucleation states for solar-blind and visible-blind dual-band UV photodetectors

High Mg-content single-phase wurtzite Mg0.51Zn0.49O (W-Mg0.51Zn0.49O) films were realized by radio frequency (RF) magnetron sputtering technique on quartz (SiO2) substrates. The metal-semiconductor-metal (MSM) solar-blind (SB) and visible-blind (VB) dual-band ultraviolet (DB-UV) photodetectors (PDs) were also fabricated based on heteroepitaxial growth of W-Mg0.51Zn0.49O films on ZnO buffer layer (BL) at different nucleation states. Under 270 nm of irradiation, the Au/Mg0.51Zn0.49O/ZnO (30 min) PD exhibited an optimal external quantum efficiency (EQE, 304.4%) and specific detectivity (1012), which indicated that the ZnO BL obtained with a 30 min treatment time was most efficient to improve the detection of SB-UV wavelength. The origin of these results was attributed to the contact area and adhesion strength between MgZnO and ZnO matrices. The results showed a feasible way to obtain high Mg-content wurtzite MgZnO alloys and performance improvement through ZnO BL, which is favorable to the applicability in SB/VB DB-UV PDs.