Flexible UV Photodetector Research Articles

Effect of thiourea concentration on the structural, optical and photoelectric properties of ZnO/ZnS/PVC composite films used as flexible UV photodetectors

Effect of thiourea concentration on the structural, optical and photoelectric properties of ZnO/ZnS/PVC composite films used as flexible UV photodetectors

Optical sensing and nonlinear optical properties of Cr-doped MoO3/PEDOT:PSS Nanocomposites

In this study, we observed a negative UV photoresponse that switched to a positive photoresponse in Cr-doped MoO3/PEDOT:PSS nanocomposite films(NCF) prepared via drop-casting. MoO3 and Cr-doped MoO3 were synthesized using a hot oil bath co-precipitation method, combined with PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)), and coated onto flexible OHP sheets. The open aperture z-scan method investigated the nonlinear optical properties of NCF on the glass substrate. The films were characterized by X-ray diffraction, scanning electron microscopic (SEM), UV–Vis spectroscopy, and Fourier Transformed Infrared (FTIR). Chromium doping caused minor changes in lattice parameters, crystalline size, and microstrain. UV spectroscopy revealed an increase in bandgap with higher Cr–MoO3 concentrations. The photoresponse of different Cr–MoO3 concentrations showed an initial current decrease under UV light, but the photoresponse became positive beyond a threshold and continued to improve. Nonlinear optical studies indicated saturable absorption in the nanocomposite. This work enhances our understanding of Cr-doped MoO3/PEDOT:PSS nanocomposites, contributing to advancements in flexible UV photodetectors and nonlinear optical applications.

Inorganic Semiconductor-Based Flexible UV Photodetector Arrays Achieved by Specific Flip-Chip Bonding.

In recent years, flexible UV photodetectors (PDs) with complex environmental adaptability and great wearability have attracted the attention of researchers worldwide. Wide bandgap inorganic semiconductor materials with excellent optoelectronic properties and mechanical stability are key functional materials for UV PD devices. However, the high temperature processing and inherent brittleness limit the further application of high-quality inorganic semiconductors in the field of flexible optoelectronics. In this work, we develop a specific flip-chip bonding fabrication technique that utilizes high-temperature treated inorganic semiconductor materials for high-performance flexible UV detection devices. Leveraging this technique, a 7 × 7 pixel flexible UV photodetector array (UV-FPDA) device based on a vertical architecture Mg-doped ZnO/NiO (Mg:ZnO/NiO) heterojunction transistor is built. The UV-FPDAs exhibit a high responsivity of 75.8 A/W and an outstanding detectivity of 8.5 × 1012 Jones. Besides, the UV-FPDAs also demonstrate excellent bending stability. Furthermore, the photoresponse characteristics of each pixel are trained and learned by an artificial neural network to achieve clear imaging of UV light information. Our results provide a new pathway for the application of inorganic semiconductors in the field of high-performance flexible UV photodetection.

Flexible UV photodetector based on graphite/titanium dioxide through facile transfer of pencil drawn graphite films on desired substrates

Assembly of graphite structures through pencil drawn method is considered among the most facile and inexpensive approaches for a wide range of electronic and optoelectronic applications. However, the typical limitation of this methodology is that the films and structures can be drawn on a very limited number of substrates. Here, we report a novel methodology for the transfer of pencil drawn graphite films on desired substrate. The graphite films are transferred from cellulose paper, textile and wood paper onto flexible and transparent acrylic tape. The novel wood paper substrate is also used for the fabrication of bar device using a mask which is then transferred onto the acrylic tape. TiO2 nanoparticles paste is coated on the surface of transferred bar device. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis, and UV–visible spectroscopy of graphite and graphite/TiO2-NPs electrodes are performed respectively to study their morphological, compositional, structural and optical features. The fabricated device acts as a UV photodetector and delivers a photocurrent as higher as 197.68 μA, photoresponsivity of 8.94 mA W−1, detectivity of 4.16 × 109 Jones at bias voltage of 5 V, response time of ∼860 ms and recovery time of ∼890 ms. The flexibility of the demonstrated photodetector is evaluated through recording changes in photocurrent under bending positions from 0 to 150°, and after employing bending cycles up to 1000. The results show that the fabrication of photodetector is facile and low-cost, and it offers valuable working compatibility under bending strains. Moreover, the flexibility of photodetectors enables their effective integration with human skin and clothes for human health monitoring applications.

Flexible UV photodetector based on copper tetraiodogallate (CuGaI4) film

AbstractThe Cu‐based halide semiconductor CuGaI4 was prepared by a high‐temperature melting method. Optoelectronic characterization and density functional theory calculations of CuGaI4 reveal a direct bandgap of 2.9 eV. The corresponding UV photodetector (PD) based on CuGaI4 demonstrates excellent UV response and rapid response time. In addition, a flexible PD based on CuGaI4 is prepared, which also displays excellent photoresponse characteristics and mechanical stability. This work provides a systematic study of this novel Cu‐based halide semiconductor and demonstrates the great potential of CuGaI4 for future UV optoelectronic devices.

Two-dimensional H4Nb6O17 for transparent and flexible UV photodetectors

We first report two-dimensional H4Nb6O17 nanosheets for high performance ultraviolet photodetectors (UV PDs). The H4Nb6O17 nanosheets are synthesized through a simple solid-state reaction and liquid exfoliation technique. The individual H4Nb6O17 nanosheet device displays outstanding UV-detecting performance, including high responsivity (3.8 AW−1), high detectivity (1.6 ×1012 Jones), and fast response speed (1.5/138 ms) at 300 nm light irradiation at 3 V bias. Furthermore, the H4Nb6O17 nanosheets film is fabricated via an easy drop-coating process, and shows high transparency (>75%) in the visible light range. More importantly, the H4Nb6O17 nanosheet film device exhibits satisfactory photocurrent (12 nA) and on/off ratio (100), and maintains excellent performance after many bending tests. This work not only introduce a promising candidate for UV PD, but also suggests the broad prospect of H4Nb6O17 nanosheets in wearable electronic devices in the future.

Cost‐Effective and Flexible Scalable Fabrication of WO3 UV Photodetectors with Enhanced Performance via Integrated LIG Electrodes

AbstractThe emerging flexible device technologies have fascinated the modern optoelectronic industry owing to their invincible properties such as wearable, stretchable, smart, energy‐efficient, scalability, cost‐effective, and high performance. However, there is still room for improvements such as performance, reliability, and mass production. This research work fabricates laser‐induced graphene (LIG) interdigitated electrodes based on flexible UV photodetectors over polyimide substrate, using solution‐processed tungsten oxide (WO3) thin film as photoactive material. The best device performance is achieved through the optimization of laser power for the deposition of LIG, as well as a different solvent for WO3. The device shows excellent photoresponsivity, external quantum efficiency, and specific detectivity of 500 mA W−1, 164%, and 3.09 × 1012 Jones, respectively. Moreover, a fast response time, such as 0.3 ms for 375 nm light, is observed. This study offers a comprehensive elucidation of the intricate process through which photoelectrons are moved toward WO3 facilitated by the electric field present at the interface of the LIG and WO3.

A self-powered flexible UV photodetector based on an individual ZnO-amorphous Ga2O3 core–shell heterojunction microwire

The photoelectric performance of a ZnO-a-Ga2O3 core–shell microwire can remain basically unchanged at different bending angles and bending cycles, indicating the potential application of the device in the field of flexible electronics.

Flexible and Self-Powered Solar-Blind UV Photodetector Based on the Ti/α-Ga2O3/Electrolyte Heterojunction with High Stability

Flexible and Self-Powered Solar-Blind UV Photodetector Based on the Ti/α-Ga₂O₃/Electrolyte Heterojunction with High Stability

Transferable 3C-SiC nanowire network film for high performance flexible UV photodetectors with a simple, low cost and large scale production

Transferable 3C-SiC nanowire network film for high performance flexible UV photodetectors with a simple, low cost and large scale production

ZnO-Based Flexible UV Photodetector for Wearable Electronic Applications

ZnO-Based Flexible UV Photodetector for Wearable Electronic Applications

Self-powered flexible UV photodetectors based on MOCVD-grown Ga2O3 films on mica

Self-powered flexible UV photodetectors based on MOCVD-grown Ga2O3 films on mica

High-performance flexible UV-photodetector via self-assembled ZnO films

Zinc oxide (ZnO) is one of the most attractive materials for the preparation of ultraviolet photodetectors (UV PDs). However, the high leakage current and slow response speed significantly limit the practical applications of ZnO-based PDs. In this study, the fabrication of UV PDs based on self-assembled ZnO film has been proposed. The device has an ultra-low dark current (25 pA@10 V) and exhibits fast response speed (190 ms/68.6 ms) and high detectivity (1.91 × 1014 Jones) for 360 nm light. The high performance can be attributed to the operating mechanism of ‘light-induced reduction of junction barrier height’. The analysis based on the thermionic emission theory indicates that illumination can significantly reduce both the Schottky barrier height and series resistance of the device. The prepared flexible PD based on the self-assembled film not only maintains excellent detection performance but also has strong durability and mechanical robustness. After 1000 bending-recovery cycles, the flexible device exhibits excellent repeatable on/off photo-switching behaviors. The measured time-response curves of the flexible PD under five different bending states show unaffected photocurrent, demonstrating excellent flexibility and stability.

Enhanced property of flexible UV photodetectors based on electrospinning ZnO–SnO2 heterojunction nanofibers by the formation of Zn2SnO4

Developing new photodetectors with good photoresponse, high stability, flexibility, and minimalization is urgently demanded facing the rapid development of optical technology. In this work, ZnO–SnO2 heterojunction nanofibers are synthesized by electrospinning. The flexible UV micro-photodetector is fabricated by combining ZnO–SnO2 heterojunction nanofibers with photolithography-patterned Au microelectrodes on PI substrate. An extremely low dark current (∼10−11 A) is obtained due to the formation of Zn2SnO4 layer at the large interface of ZnO–SnO2 heterojunctions. Upon exposure to UV light with power density of 24 μW cm−2, the photodetector exhibits high on–off ratio of ∼104, high responsibility of 267 A W−1, and fast response speed of 2.75 s. The photodetector has good photoelectric properties and high UV selectivity. Moreover, the flexibility of the UV photodetector is demonstrated. The photoresponse remains ∼60% of the initial level even under a large bending angle of 45°. The combined utilization of electrospinning and photolithography is convenient to fabricate flexible UV photodetectors.

Highly-Sensitive, Flexible, and Self-Powered UV Photodetectors Based on Perovskites Cs₃Cu₂I₅/ PEDOT: PSS Heterostructure

Herein, we demonstrate a highly-sensitive, flexible, and self-powered UV photodetector based on perovskites Cs3Cu2I5/PEDOT: PSS heterostructure. The device shows a high photoresponsivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}$ </tex-math></inline-formula> ) of 170.3 mA/W, on/off ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.7\times 10^{{3}}$ </tex-math></inline-formula> , response/recovery time of 177.0/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$195.2 \mu \text{s}$ </tex-math></inline-formula> , and good specific detectivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}^{\ast }$ </tex-math></inline-formula> ) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0\times 10^{{13}}$ </tex-math></inline-formula> Jones to 275 nm light at self-powered mode. Benefiting from the solvent vapor annealing process, the Cs3Cu2I5 film is conformally attached to the flexible substrate and maintains relatively high performance at a curvature radius of 3 mm. Our work could pave the way to open up high-performance self-powered perovskites UV photodetector in flexible solution-based optoelectronics.

Integration of filter membrane and Ca2Nb3O10 nanosheets for high performance flexible UV photodetectors

• We first report the integration of filter membrane and Ca 2 Nb 3 O 10 nanosheets UV photodetectors (FM@CNO UV PDs). • The FM@CNO PD shows high responsivity (0.08 AW −1 ), high detectivity (1.1 × 10 12 Jones), high UV/visible rejection ratio (3.86 × 10 3 ) and fast speed (0.12/1.24 ms) under 300 nm light illumination. • The FM@CNO PD exhibits excellent flexibility after many bending cycles. And the FM@CNO array device can be used as a pixel array detector for UV imaging. We report that the integration of filter membrane and Ca 2 Nb 3 O 10 nanosheets (FM@CNO) UV photodetector (UV PD) shows high performance and excellent flexibility. The Ca 2 Nb 3 O 10 nanosheets were prepared by a facile solid-state reaction and liquid exfoliation process. The Ca 2 Nb 3 O 10 nanosheets can be integrated into the pores of a filter membrane via a simple vacuum filtration method. The FM@CNO UV PD shows high performance under 300 nm light illumination at 5 V bias, including high responsivity (0.08 AW −1 ), high detectivity (1.1 × 10 12 Jones), high UV/visible rejection ratio (3.86 × 10 3 ) and fast speed (0.12/1.24 ms). Furthermore, the FM@CNO device exhibits excellent flexibility after many bending cycles. In addition, the FM@CNO array device was used as a pixel array detector for UV imaging. This work provides a novel approach to achieve high performance flexible PDs based on filter membrane and two dimensional materials.

Characteristics of flexible ZnO nanorod UV photodetectors processed by using a direct silicon etching transfer method

A flexible UV photodetector based on ZnO NRs with good photoelectrical properties was fabricated by applying DSET to achieve superior UV-sensing properties.

Fabrication and characterization of a porous ZnO flexible UV photodetector on fiberglass and the electrode dimensions effect

In this study, three flexible metal-semiconductor-metal ultraviolet photodetectors are fabricated on the FR4 fiberglass substrate based on the porous zinc oxide by radiofrequency sputtering. Their copper electrodes were created by printed circuit board, a simple and cheap method. Here, the effect of porosity on the photodetector parameters is discussed. The results show that the difference in the finger size in the photodetectors leads to differences in the parameters. In these photodetectors, as the fingers increase in length, dark current increases from 0.25 to 67.3 µA, photocurrent from 1.98 to 208 µA, and response time from 430 to 570 ms. Also, with expanding finger width, these parameters changed 18.48 µA, 26.8 µA, and 440 ms, respectively.

Piezo-phototronic effect triggered flexible UV photodetectors based on ZnO nanosheets/GaN nanorods arrays

Here in, we report on the fabrication of a flexible ultraviolet photodetector composed of two dimensional (2D) ZnO nanosheets (NSs) and one dimensional (1D) GaN nanorods (NRs). ZnO NSs were grown on the surface of GaN NRs to form 2D/1D heterojunction via simple hydrothermal method. A striking photoresponse was observed across 2D-ZnO/1D-GaN heterojunction under UV illumination. The photoresponsitivity and detectivity of the photodetector enhanced by two order magnitude than that of 1D GaN NRs. Furthermore, under a tensile strain the photoresponsivity of this photodetector was also tuned through piezo-phototronic effect arising from ZnO NSs. Due to lowering of barrier height under the application of strain, more photogenerated electron-hole pairs can transport through the heterojunction without recombination, resulting in enhanced photorespositivity.

Optimizing the Electronic Structure of In2O3 through Mg Doping for NiO/In2O3 p-n Heterojunction Diodes.

In2O3 is a wide bandgap oxide semiconductor, which has the potential to be used as an active material for transparent flexible electronics and UV photodetectors. However, the high concentration of unintentional background electrons existing in In2O3 makes it hard to be modulated by the electric field or form p-n heterojunctions with a sufficient band-bending width at the interface. In this work, we report the reduction of the background electrons in In2O3 by Mg doping (Mg-In2O3) and thereby improve the device performance of p-n diodes based on the NiO/Mg-In2O3 heterojunction. In particular, Mg doping compensates the free electrons in In2O3 and reduces the electron concentration from 1.7 × 1019 cm-3 without doping to 1.8 × 1017 cm-3 with 5% Mg doping. Transparent p-n heterojunction diodes were fabricated based on p-type NiO and n-type Mg-In2O3. The device performance was considerably enhanced by Mg doping with a high rectification ratio of 3 × 104 and a remarkable high breakdown voltage of >20 V. High-resolution X-ray photoelectron spectroscopy was used to investigate the interfacial electronic structure between NiO and Mg-In2O3, revealing a type II band alignment with a valence band offset of 1.35 eV and a conduction band offset of 2.15 eV. A large built-in potential of 0.98 eV was found for the undoped In2O3 but decreased to 0.51 eV for 5% Mg doping of In2O3. The NiO/Mg-In2O3 diodes with an improved rectification ratio and wider depletion region provide the possibility of achieving photodetectors with rapid photoresponse.