High-performance UV Photodetectors Research Articles

Freestanding ZnO Nanowire Films Derived from Carbon Nanotube Template: Implications for High-Performance UV Photodetectors

Freestanding ZnO Nanowire Films Derived from Carbon Nanotube Template: Implications for High-Performance UV Photodetectors

ZnO@NiO core-shell heterojunction photoanode modified with NiOOH co-catalyst for high-performance self-powered photoelectrochemical-type UV photodetector

ZnO, a promising photoanode material, faces significant challenges in achieving high-efficient photoelectrochemical (PEC) type UV photodetectors due to inadequate charge separation and sluggish surface reaction kinetics. Constructing heterojunction nanostructures by coupling of p-NiO to n-ZnO nanowire arrays with well-aligned energy band positions presents a feasible strategy for enhancing PEC-type photodetector performance. Herein, we demonstrate that the designed ZnO@NiO core–shell nanowire arrays form a spatial charge transfer channel, facilitating efficient generation and extraction of charge carriers. The exceptional catalytic properties of NiOOH, derived from the transformation of NiO in an aqueous alkaline environment, serve as a potent co-catalyst, effectively accelerating the kinetics of the surface oxygen evolution reaction. Benefiting from the synergistic effect of the heterojunction and cocatalyst, the optimized photoanode achieves a high responsivity of 438.36 mA/W, a large detectivity of 4.85 × 1012 Jones, and rapid response time of 150.05/150.26 ms, while simultaneously exhibiting long-time PEC stability. This work highlights the critical role of nanostructure design in developing high-performance self-powered UV photodetectors.

Self-powered high performance UV photodetectors based on spin coated n-ZnO/p-Si heterostructure

Self-powered photodetectors with high responsivity and external quantum efficiency (EQE) are in great demand for various practical applications. This paper reports the fabrication and evaluation of self-powered, high-performing ultraviolet photodetectors with fast switching action. A p-n junction was formed by spin coating n-type ZnO on p-silicon substrates. The photodetector showed a responsivity of 0.15 A/W and an EQE of 52 %. The switching speed of devices was as low as 250 ms, even under zero bias. XRD analysis revealed the hexagonal wurtzite structure and AFM images confirmed the good quality of the films with roughness values as low as 2 nm. Defect analysis was done by photoluminescence studies. The molarity of the precursor solution and the annealing temperature were varied to optimize the performance. Sample with molarity 0.5 M annealed at 500 °C showed the best results.

High-performance solar-blind UV bipolar junction phototransistor based on a vertical Pt/Ga2O3/p-Si Schottky emitter structure

Solar-blind UV photodetectors are extensively applied in both military and civilian domains. In this work, a high-performance Pt/Ga2O3/p-Si Schottky emitter solar-blind UV bipolar junction phototransistor is demonstrated. It exhibits a peak responsivity (@246 nm) of 1632.8 A/W under a bias of 5 V. This responsivity is significantly enhanced compared to the Al/Ga2O3/p-Si heterojunction photodetector, while its response speed remains largely unchanged. Additionally, the device demonstrates excellent solar-blind UV spectral selectivity, with a solar-blind UV to visible-blind UV rejection ratio (R246 nm/R365 nm) reaching 2.4×104. This work provides new insights into the design and fabrication of high-performance Ga2O3-based solar-blind UV photodetectors.

Boosting deep-ultraviolet photodetector performance via ferroelectric effect based on HfAlOx@PEI composite

In this study, hafnium-aluminum oxide (HfAlOx) was used as an effective active layer in a self-powered deep-ultraviolet (UV) photodetector. For the first time, we exploited the ferroelectric properties of crystalline HfAlOx to enhance device performance. The HfAlOx powder obtained at an annealing temperature of 850 °C exhibited the highest-intensity peak for the orthorhombic phase (o-phase), representing the ferroelectric property of the material. The HfAlOx particles were reduced to a small size using mechanical treatment to facilitate the preparation of a composite thin film with a polyethyleneimine (PEI) polymer matrix. First, the HfAlOx@PEI composite film-based photodetector demonstrated a remarkable on/off ratio of more than 103 and a rapid response (trise/tfall of 0.127/2.7 s) at zero bias under 254-nm UV illumination. Second, the photocurrent of the device was dramatically boosted under an external bias owing to the injection of carriers, supported by the ferroelectric effect of the o-phase HfAlOx. As a result, the external quantum efficiency and responsivity approached 2628 % and 5.37 A/W at −1 V bias, respectively. Furthermore, the device exhibited excellent photostability, demonstrating almost no change in the photocurrent after 1000 s of UVC irradiation. Our findings provide guidance for the preparation of optoelectronic devices, particularly self-powered high-performance UV photodetectors.

One-Dimensional ZnO Nanorod Array Grown on Ag Nanowire Mesh/ZnO Composite Seed Layer for H2 Gas Sensing and UV Detection Applications.

Photodetectors and gas sensors are vital in modern technology, spanning from environmental monitoring to biomedical diagnostics. This paper explores the UV detection and gas sensing properties of a zinc oxide (ZnO) nanorod array (ZNA) grown on silver nanowire mesh (AgNM) using a hydrothermal method. We examined the impact of different zinc acetate precursor concentrations on their properties. Results show the AgNM forms a network with high transparency (79%) and low sheet resistance (7.23 Ω/□). A sol-gel ZnO thin film was coated on this mesh, providing a seed layer with a hexagonal wurtzite structure. Increasing the precursor concentration alters the diameter, length, and area density of ZNAs, affecting their performance. The ZNA-AgNM-based photodetector shows enhanced dark current and photocurrent with increasing precursor concentration, achieving a maximum photoresponsivity of 114 A/W at 374 nm and a detectivity of 6.37 × 1014 Jones at 0.05 M zinc acetate. For gas sensing, the resistance of ZNA-AgNM-based sensors decreases with temperature, with the best hydrogen response (2.71) at 300 °C and 0.04 M precursor concentration. These findings highlight the potential of ZNA-AgNM for high-performance UV photodetectors and hydrogen gas sensors, offering an alternative way for the development of future sensing devices with enhanced performance and functionality.

Enhanced ultraviolet photodetection with Ag nanoparticle-decorated ZnO nanowires and core-shell electrodes

Our study presents the synthesis and characterization of one-dimensional (1-D) zinc oxide (ZnO) nanorod (NR) arrays via low-temperature hydrothermal synthesis, followed by surface modification with silver nanoparticles (Ag NPs). Silver nanowires (AgNWs) are potential alternatives to indium-tin oxide, but their poor stability in atmospheric conditions poses a challenge. To address this, we developed ultrathin Ag/ZnO core-shell structured nanowire networks for ultraviolet-photodetectors (UV-PDs). This cost-effective solution process yielded high transmission (77 %) and low sheet resistance (8.3 Ω/sq). We comprehensively investigated surface morphology, crystalline nature, elemental composition, optical properties, and electrical performance of both synthesized nanorod arrays and NW networks. The UV photodetector exhibited a rise time of approximately 1.35 s and a decay time of 8.01 s, both faster than pristine AgNW electrodes. Additionally, the dark current decreased from 9 nA to 3.5 nA after incorporating Ag/ZnO, accompanied by a significant improvement in photocurrent. These results highlight a promising approach for high-performance UV photodetectors, leveraging the stability and conductivity of Ag/ZnO core-shell NW networks.

High performance of UV photodetectors by integration of plasmonic Ag nanoparticles on GaN

High-performance ultraviolet photodetectors have attracted much attention due to their various potential applications from household to universal. On basis of this, in this work, a high – performance and photoresponse enhancement UV photodetector based on Ag NPs/GaN heterojunction was demonstrated. By incorporating of Ag nanoparticles, light confinement determined by Ag nanostructure offers an effective approach to break through the limitation of the light-mater interaction within the photoactive layers of photodetector. Various size and elemental composition of Ag NPs are fabricated on GaN lead to significant enhancement of photocurrent in UV photodetector. Consequently, an outstanding photoresponsivity of 89 A/W, external quantum efficiency of 2.8 × 103% at low bias voltage of 0.3 V were achieved. The improve photo-response of the Ag NPs-decorated GaN-based photodetector is attributed to the simultaneous effect of strong plasmon absorption, increased injection of hot electrons into the conduction band of GaN. This study will open up the direction to fabricate the high-performance UV photodetector.

High-performance Ga2O3 solar-blind UV photodetectors via film growth regulation and surface state engineering

Gallium oxide (Ga2O3) with a wide bandgap is emerging as one of the most promising candidates for solar-blind photodetectors (SBPDs). However, the practical application of Ga2O3-based SBPDs is impeded by substantial defects-related leakage currents, sluggish response speed, and high-cost, making their practical applications face great challenges. Here, we proposed strategic films growth regulation and surface state engineering to grow high-quality yet economical β-Ga2O3 films, thereby achieving high-performance SBPDs. High-resolution transmission electron microscopy revealed the presence of high-quality films with an extremely regular arrangement of β-Ga2O3 (2‾01) planes. The full width at half maximum and root mean square roughness values are 0.07° and 0.716 nm, respectively. The β-Ga2O3 films demonstrated a significant reduction in VO concentrations after O2/N2 plasma treatment. This process can effectively minimize thermal damage to the sample surface while retaining highly reactive free radicals. The photocurrents of devices can be further enhanced, leading to a larger PDCRs of 8.6 × 107, through N2 plasma treatment. Moreover, the films effectually suppress the persistent photoconductivity effect with τr and τd values of 5.31/0.97 s and 0.49/0.87 s before and after N2 plasma treatment, respectively. We have demonstrated the influence mechanism of O2/N2 plasma treatment on photoelectronic performance. This study provides a practical approach to growing high-quality β-Ga2O3 films and preparing high-performance but low-cost Ga2O3-based SBPDs.

High-performance and low-power consumption deep UV photodetectors based on MOCVD-grown ZnGa2O4epilayers with high temperature functionality

This work reports on the fabrication of excellent quality deep ultraviolet photodetectors (DUV PDs) based on metalorganic chemical vapor deposition (MOCVD) grown spinel ZnGa2O4 thin films on c-plane sapphire. Herein, The DUV PDs by exhibiting an ultra-low dark current of 6.69 fA and a high photo-to-dark-current ratio (PDCR) of >108 at a low-power operation of 0.2 V. While PDCR reached more than 109 on applied bias of 10 V having extremely low dark current of 37 fA. The detector revealed an ultra-high responsivity of 185 and 3.53 A/W under the exposure of 107 μW/cm2 of 245 nm wavelength at room temperature (RT) and applied bias of 10 and 0.2 V, respectively, and exhibited the record-high detectivity of the order of 1017 Jones. The temperature-dependent operation remained stable across a wide temperature range, from 27 °C to 125 °C, maintaining ultra-low dark current. The nearly constant growth and decay time of DUV PDs throughout the temperature range emphasizes the robustness and reliability of PD. The ideality factor in both DUV and dark conditions nearing unity proves the dominance of the thermionic emission mechanism. Also shows the stable and slight improved performance after a year. Therefore, these findings suggest that ZnGa2O4 is a strong contender for deep UV detection that shows robustness even at high temperatures.

High-performance self-powered UV photodetectors using SnO2 thin film by reactive magnetron sputtering

Self-powered UV photodetector (UVPD) operates without the need for an external energy source and contributes to global energy conservation. With ongoing innovation, self-powered PDs are becoming increasingly appealing for industrial and innovation applications such as advanced environmental monitoring and communication devices. This study investigates the influence of varying working pressures (ranging from 3 to 15 mTorr) during reactive magnetron sputtering on the crystalline structure, surface morphology, and performance of SnO2 thin film photodetectors, aiming to fabricate self-powered UVPDs. The SnO2-based UVPD demonstrates exceptional self-powered UV photodetection capabilities, characterized by a sensitivity of 6.41×105%, responsivity of 0.09 mA/W, and detectivity of 2.99×1010 Jones. In addition, SnO2-based UVPD possesses a switching photo response and recovery time of 0.75 and 0.99 s. Henceforth, it was observed that 8 mTorr SnO2 thin film exhibits exceptional stability, superior photodetector performance, and remarkable repeatability, rendering them highly suitable for UVPD applications. Notably, these films demonstrate sustained functionality for approximately 100 days without necessitating encapsulation. These excellent results confirm that SnO2 thin films are suitable for fabricating future smart optoelectronics devices.

Plasmon-exciton interactions in ZnO/AuNPs heterostructure film for high photoconductivity

This study investigatesplasmon-exciton interactions within ZnO/AuNPs heterostructure films. Elemental, structural, and morphological analyses validate the successful formation of these films. The observed shift in the plasmonic resonance band and absorption edge otowards the red region the red region is attributed to strong surface plasmon damping influenced by exciton interactions within ZnO. Irradiation with blue light induces plasmonic electrons, generation in the ZnO/AuNPs film, enhancing electrical conductivity through interaction with ZnO excitonic states. UV light irradiating generates the electron-hole pair in the ZnO film and interacts with the free electrons in AuNPs. The ZnO/AuNPs heterostructure films hold promise for applications such as high-performance UV-photodetectors, photoactive layers in solar cells, light-emitting diodes, and energy storage devices.

Developing a high-performance UV photodetector by improving polyaniline polymer properties with multi-walled carbon nanotubes

Developing a high-performance UV photodetector by improving polyaniline polymer properties with multi-walled carbon nanotubes

Air-Stable Self-Driven UV Photodetectors on Controllable Lead-Free CsCu2I3 Microwire Arrays.

The rapid evolution of the Internet of Things has engendered increased requirements for low-cost, self-powered UV photodetectors. Herein, high-performance self-driven UV photodetectors are fabricated by designing asymmetric metal-semiconductor-metal structures on the high-quality large-area CsCu2I3 microwire arrays. The asymmetrical depletion region doubles the photocurrent and response speed compared to the symmetric structure device, leading to a high responsivity of 233 mA/W to 355 nm radiation. Notably, at 0 V bias, the asymmetric device produces an open-circuit voltage of 356 mV and drives to a short-circuit current of 372 pA; meanwhile, the switch ratio (Iph/Idark) reaches up to 103, indicating its excellent potential for detecting weak light. Furthermore, the device maintains stable responses throughout 10000 UV-light switch cycles, with negligible degradation even after 90-day storage in air. Our work establishes that CsCu2I3 is a good candidate for self-powered UV detection and thoroughly demonstrates its potential as a passive device.

Dual-coupling effect enables a high-performance self-powered UV photodetector.

Self-powered ultraviolet photodetectors generally operate by utilizing the built-in electric field within heterojunctions or Schottky junctions. However, the effectiveness of self-powered detection is severely limited by the weak built-in electric field. Hence, advances in modulating the built-in electric field within heterojunctions are crucial for performance breakthroughs. Here, we suggest a method to enhance the built-in electric field by taking advantage of the dual-coupling effect between heterojunction and the self-polarization field of ferroelectrics. Under zero bias, the fabricated AgNWs/TiO2/PZT/GaN device achieves a responsivity of 184.31 mA/W and a specific detectivity of 1.7 × 1013 Jones, with an on/off ratio of 8.2 × 106 and rise/decay times reaching 0.16 ms/0.98 ms, respectively. The outstanding properties are primarily attributed to the substantial self-polarization of PZT induced by the p-GaN and the subsequent enhancement of the built-in electric field of the TiO2/PZT heterojunction. Under UV illumination, the dual coupling of the enhanced heterojunction and the self-polarizing field synergistically boost the photo-generated carrier separation and transport, leading to breakthroughs in ferroelectric-based self-powered photodetectors.

Sol-Gel Synthesized Amorphous (InxGa1−x)2O3 for UV Photodetection with High Responsivity

β-Ga2O3 photodetectors have the advantages of low dark current and strong radiation resistance in UV detection. However, the limited photocurrent has restricted their applications. Herein, MSM UV photodetectors based on (InxGa1−x)2O3 (x = 0, 0.1, 0.2, 0.3) by a sol-gel method were fabricated and studied. The doping of indium ions in Ga2O3 leads to lattice distortion and promotes the formation of oxygen vacancies. The oxygen vacancies in (InxGa1−x)2O3 can be modulated by various proportions of indium, and the increased oxygen vacancies contribute to the enhancement of electron concentration. The results show that the amorphous In0.4Ga1.6O3 photodetector exhibited improved performances, including a high light-to-dark current ratio (2.8 × 103) and high responsivity (739.2 A/W). This work provides a promising semiconductor material In0.4Ga1.6O3 for high-performance MSM UV photodetectors.

High-performance UV photodetector based on nickel oxide loaded with low amount of nitrogen and boron co-doped reduced graphene oxide for bias-switchable photoconductance

In this work, we report a low cost and straightforward chemical synthesis of nickel oxide nanoparticles decorated with low amount of nitrogen and boron co-doped reduced GO for a high-performance UV photodetector. For the first time, NiO/NB-rGO nanomaterial was synthesized following the co-precipitation method and subsequently annealed at 400 °C. The nanomaterial was characterized with several techniques such as SEM, TEM, XRD, and Raman spectroscopy. In addition, the device was subjected to electrical characterizations to determine their responsivity, detectivity, and temporal responses both in the absence of illumination (dark conditions) and under UV illumination of 375 nm. In particular, the studied I-V curve was performed to evaluate the coexistence of positive and negative photoconductivity in our device. The results revealed a better photoresponse of NiO/NB-rGO device to UV light, which showed high responsivity (800 A/W), large detectivity (9.4 ×1011 Jones), and fast rise/fall time (1.38/2.17 s) at reverse bias. Consequently, the Schottky contact of NiO/NB-rGO allowed to switch between carriers’ conduction, which displayed both positive and negative photoconductance at reverse and forward bias.

Interface modification of MoS2/ZnO heterojunction for controllable electron flow and fabrication of high-performance UV photodetectors with fast response/recovery speed

Hetero-structured thin films, MoS2/ZnO thin films, were fabricated by adding MoS2 films under the ZnO thin films via sol-gel spin-coating method; ZnO nanoparticles were observed on the surface of sol-gel spin-coated ZnO thin films. Although ZnO nanoparticles were observed on the surface of hetero-structured thin films, the surface area of the hetero-structured thin films was higher than ZnO thin films owing to the high surface roughness of the MoS2 films. Three diffraction peaks were observed in the hetero-structured thin films at 31.74°, 34.38°, and 36.22°, which indicates heterostructure was polycrystalline, and the heterostructure was formed successfully. When the UV photodetector was fabricated by using hetero-structured thin films, the enhanced values of photocurrent, photoresponsivity and photosensitivity were observed. In addition, the hetero-structured thin films exhibited a faster response/recovery speed because the move of electrons and holes during UV illumination. Thus, it was concluded that the interface modification of the MoS2/ZnO heterojunction is an effective solution for overcoming the drawbacks of ZnO-based UV photodetectors. This approach can be considered a novel method for high-performance optoelectronics with fast response speed applicable to various fields.

An efficient MSM UV photodetector with an ultra-low dark current enhanced by a back to back TiO2/PbTiO3 PN heterojunction

A TiO2 MSM UV photodetector has been extensively researched and exhibits many good properties such as stability and a large ratio of light to dark current. However, it suffers from a high dark current and slow response and recovery. In this work, an MSM UV photodetector based on a TiO2/PbTiO3 heterojunction was fabricated by a sol-gel method. Spontaneous polarization of ferroelectric perovskite PbTiO3 can deplete carriers and accelerate the separation and transport of photo-generated carriers. The photodetector showed enhanced performances, including an ultra-low dark current (1.146 19 × 10−11 A), an improving ratio of light to dark current, as well as short response and recovery times (decreasing to 65 and 81 ms). These results indicate the potential in the combination of ferroelectric perovskite PbTiO3 with traditional wide bandgap semiconductor materials to fabricate high-performance UV photodetectors.

Two-dimensional perovskite NdNb2O7 for high-performance UV photodetectors by a general exfoliation and assembly strategy

Two-dimensional (2D) oxide perovskites show great promise as candidates for future optoelectronic devices. For the first time, we have successfully exfoliated 2D perovskite NdNb2O7 (NNO) nanosheets by a solid-state calcination and liquid-phase exfoliation method. The individual NNO nanosheet photodetector (PD) demonstrates outstanding performance in detecting UV light (260 nm, 3 V), including high responsivity (62 AW−1), high detectivity (6.7 *1012 Jones), high spectral selectivity (R260/R400= 9000), fast response speed (0.1/7.8 ms) and long-term stability. Furthermore, through a simple interface self-assembly technique, we have successfully achieved orderly and flat films of NNO nanosheets. The resulting film exhibits high transparency (>75 %) in the visible light range. The NNO film device demonstrates excellent performance after undergoing numerous bending tests. This work not only presents a new candidate for high-performance and high-stability UV photodetectors but also introduces a general exfoliation and assembly strategy.