Flexible Photodetectors Research Articles

Flexible self-powered solar-blind Schottky photodetectors based on individual Ga2O3 microwire/MXene junctions

Flexible solar-blind Schottky photodetectors made of individual β-Ga2O3 microwires (MWs) and Ti3C2Tx (MXene) on a PET substrate are designed.

High-performance flexible and self-powered perovskite photodetector enabled by interfacial strain engineering

The spin–orbit coupling (SOC) strength in a perovskite film is enhanced by regulating the lattice strain with PDCBT layer, resulting in a high-performance flexible and self-powered perovskite photodetector.

Highly stable, substrate-free, and flexible broadband halide perovskite paper photodetectors.

In this work, we aim to fabricate a highly stable and flexible perovskite paper photodetector based on a Zn-doped MA0.6FA0.4PbI3 perovskite and CNC. The paper photodetector has been successfully synthesized by the vacuum filtration method and deposited with interdigitated electrodes. The paper photodetector exhibits a significant photoresponse with a responsivity of 0.23 A W-1 under 650 nm light irradiation when operated at 5 V. The stability of the paper photodetector has also been tested and it shows high photoresponse after 30 days under ambient conditions. Therefore, this paper photodetector holds promise for developing efficient, stable, and flexible optoelectronic devices in the future.

Development of a paper-based wearable UV photo-detector device using ZnO nanostructure

We depict an exceedingly low-cost and flexible photodetector in this work employing ZnO nanostructures grown on Whatman filter paper as the substrate and pencil-drawn graphite as the electrodes with a gap of 1 mm between the electrodes. A semi-non-aqueous solution containing Zinc acetate ((CH3COO)2Zn·2H2O) is used to deposit ZnO thin film on paper. The graphite/ZnO/graphite device shows a noticeable increase in the photo-current under UV (253 nm) light of the intensities in the range from 6 to 100 µW/cm2 with a higher Ip/Id ratio of 7800 at 30 V. This device shows higher responsivity of 1.94 A/W for the lowest incident intensity of UV light (6 µW/cm2). The best rise (tr) and decay time (td) for this photodetector was ∼ 13 ms. Based on the results and the non-toxic/hazardous nature of the substrate, this device shows promising UV photodetection performance under ambient conditions and is found suitable for wearable devices to protect humans from getting exposed to harmful UV radiation.

MXene based flexible photodetectors: progress, challenges, and opportunities.

The growing interest in applying 2D transition-metal carbides and nitrides (MXenes) to diverse application fields such as energy storage and harvesters, catalysts, sensors, optoelectronics, electromagnetic interference shielding and antennas since its first discovery in 2011 is clearly evident. Their intrinsic high conductivity limits the development of MXenes in photodetectors that rely on the semiconducting properties of active materials, while the abundant functional groups on the surface of MXenes provide opportunities for using MXenes as sensing materials in the fabrication of flexible photodetectors. Considerable studies on MXene based photodetectors have been carried out, but the main obstacles include seeking novel semiconducting materials in MXene families, the manufacturing technology, etc. This review highlights the progress, challenges and opportunities in MXene based flexible photodetectors and discusses novel materials, architectures, and approaches that capitalize on our growing understanding of MXenes.

Interaction between pentacene molecules and monolayer transition metal dichalcogenides.

Using first-principles calculations based on density-functional theory, we investigated the adsorption of pentacene molecules on monolayer two-dimensional transition metal dichalcogenides (TMD). We considered the four most popular TMDs, namely, MoS2, MoSe2, WS2 and WSe2, and we examined the structural and electronic properties of pentacene/TMD systems. We discuss how monolayer pentacene interacts with the TMDs, and how this interaction affects the charge transfer and work function of the heterostructure. We also analyse the type of band alignment formed in the heterostructure and how it is affected by molecule-molecule and molecule-substrate interactions. Such analysis is valuable since pentacene/TMD heterostructures are considered to be promising for application in flexible, thin and lightweight photovoltaics and photodetectors.

Synthesis of multiphase MoS2 heterostructures using temperature-controlled plasma-sulfurization for photodetector applications.

Two-dimensional (2D) materials exhibit outstanding performance in photodetectors because of their excellent optical and electronic properties. Specifically, 2D-MoS2, a transition metal dichalcogenide, is a prominent candidate for flexible and portable photodetectors based on its inherent phase-dependent tunable optical band gap properties. This research focused on creating high-performance photodetectors by carefully arranging out-of-plane 2D heterostructures. The process involved stacking different phases of MoS2 (1T and 2H) using controlled temperature during plasma-enhanced chemical vapor deposition. Among the various phase combinations, the best photocurrent response was obtained for the 1T/2H-MoS2 heterostructure, which exhibited an approximately two-fold higher photocurrent than the 2H/1T-MoS2 heterostructure and 2H/2H-MoS2 monostructure. The 1T/2H-MoS2 heterostructure exhibited a higher photoresponse than the monostructured MoS2 of the same thickness (1T/1T- and 2H/2H-MoS2, respectively). The effect of the stacking sequences of different phases was examined, and their photoperformances were investigated. This study demonstrates that phase engineering in 2D-MoS2 van der Waals heterostructures has significant potential for developing high-performance photodetectors.

Scale-up synthesis of high-quality solid-state-processed CsCuX (X = Cl, Br, I) perovskite nanocrystal materials toward near-ultraviolet flexible electronic properties.

High-quality CsCu2X3 and Cs3Cu2X5 (X = Cl, Br, I) nanocrystals (NCs) exhibit excellent optoelectronic, physical, and chemical properties for detection of UV radiation due to large carrier mobility and lifetime, and heavy atoms. The nanocrystal materials can be prepared via a low-cost and simple solid-state synthesis. However, poor reproducibility and complex synthesis methods of obtaining perovskite NC thin films represent a drawback for the fabrication of the commercial photoelectric device. To address these issues, we develop highly stable CsCu2X3 and Cs3Cu2X5 NC materials using a facile solid-state reaction method for the scale-up production of halogen lead-free perovskites. We suggest a distinctive way to design a series of nanocrystalline perovskites using short-term synthesis and study the mechanism of perovskite formation using thermal solid-state synthesis. These all-inorganic and lead-free CsCu2X3 and Cs3Cu2X5 exhibit large photoluminescence quantum yields (PLQYs) up to 95.2%. Moreover, flexible paper photodetectors based on this series of lead-free perovskites show strong photoselectivity and bending stability at 254 nm, 365 nm, and 405 nm wavelengths. High-quality responses with a responsivity of 1.1 × 10-3 A W-1 and detectivity of 2.71 × 109 jones under UV illumination (10 μW cm-2) at a bias voltage of 5 mV are demonstrated. These results open prospects for designing photodetectors, LEDs, and other photosensitive devices.

Research progress of silicon nanowires array photodetectors

As one of the most important semiconductor materials, silicon (Si) is widely used in optoelectronic devices such as solar cells and photodetectors. Owing to the difference in refractive index between silicon and air, a large amount of incident light is reflected back into the air from the silicon surface. In order to suppress the loss caused by this reflection, a variety of silicon nanostructures with strong trapping effect have been developed. Most of the dry-etching schemes encounter the problems of high cost and complex preparation, while the silicon nanowires array prepared by the wet-etching schemes has the problems of low controllability of some parameters such as the spacing between two adjacent nanowires, and the small effective area of heterojunction. The method of using polystyrene microsphere as the mask can integrate the advantages of dry-etching method and wet-etching method, and it is easy to obtain periodic silicon nanowires (pillars) array. In this paper, first, we summarize the properties and preparation methods for silicon nanowires structure, the strategies to effectively improve the performance of silicon nanowires (pillars) array photodetectors, Then we analyze the existing problems. Further, the latest developments of silicon nanowires (pillars) array photodetector are discussed, and the structure, morphology of photosensitive layer and methods to improve the performance parameters of silicon nanowires (pillars) array photodetector are analyzed. Among them, we focus on the ultraviolet light sensitive silicon based photodetector and its method to show tunable and selective resonance absorption through leaky mode resonance, the silicon nanowires array photodetector modified with metal nanoparticles and the method of improving performance through surface plasmon effect, and plasmon hot electrons. Heterojunction photodetectors composed of various low-dimensional materials and silicon nanowires (pillars) array, and methods to improve the collection efficiency of photogenerated charge carriers through the “core/shell” structure, methods to expand the detection band range of silicon-based photodetectors by integrating down-conversion light-emitting materials and silicon nanowires (pillars) array, flexible silicon nanowires array photodetectors and their various preparation methods, are all introduced. Then, the main problems that a large number of defect states will be generated on the silicon nanostructure surface in the MACE process are briefly introduced, and several possible solutions for defect passivation are also presented. Finally, the future development for silicon nanowires (pillars) array photodetectors is prospected.

Flexible self-powered photoelectrochemical-type photodetectors based on Bi2O2S/GO composites

Flexible Bi2O2S/GO photodetector with KOH quasi-solid electrolyte demonstrates excellent photoresponse and mechanical flexibility. It also shows outstanding, stable self-powering capabilities without an external power supply.

Fast-response self-powered flexible transparent ultraviolet photodetectors based on a CuO/ZnO nanowire array heterojunction

A self-powered flexible transparent ultraviolet photodetector based on a CuO/ZnO nanowire array heterojunction is successfully fabricated, which exhibits fast-response speed, high transparency and superior mechanical stability.

Au decorated ultrathin WS2-based single-electrode triboelectric nanogenerator for flexible self-powered photodetector

Au decorated ultrathin WS2-based single-electrode triboelectric nanogenerator for flexible self-powered photodetector

Recent Progress of Flexible Photodetectors Based on Low‐Dimensional II–VI Semiconductors and Their Application in Wearable Electronics

AbstractFlexible photodetectors exhibit many advantages such as a good bendability, foldability, and even stretchability as well as weight light, which have triggered a widely concerned in wearable electronics including wearable monitoring, wearable image sensing, self‐powered integrated electronics, etc. Recently, various II–VI semiconductor nanostructures have become promising candidates in flexible photodetectors due to their unique characteristics, such as direct bandgap semiconductors, excellent optical and electric properties, high quantum efficiency, and inherent mechanical flexibility. Herein, the most recent progress on low‐dimensional (0D, 1D, 2D, and related heterostructures) II–VI semiconductors based flexible photodetectors and their application in wearable electronic is reviewed. First, a brief introduction of the main sensing mechanisms and key figures of merits for photodetectors is presented. Then, the recent progresses on flexible photodetectors are provided, in which the functional materials synthesis methods are also discussed. More importantly, the applications of the flexible photodetectors are summarized, including wearable monitoring sensors, image sensors, and self‐powered integrated wearable electronics. Finally, the challenges and the future research direction of the flexible photodetectors are discussed, meanwhile the outlook for the development of flexible photodetectors in the future integration of wearable electronic is also provided.

Perovskite Solar Cell-Gated Organic Electrochemical Transistors for Flexible Photodetectors with Ultrahigh Sensitivity and Fast Response.

Photodetectors (PDs) are the building block of various imaging and sensing applications. However, commercially available PDs based on crystalline inorganic semiconductors cannot meet the requirements of emerging wearable/implantable applications due to their rigidity and fragility, which creates the need for flexible devices. Here, a high-performance flexible PD is presented by gating an organic electrochemical transistor (OECT) with a perovskite solar cell. Due to the ultrahigh transconductance of the OECT, the device demonstrates a high gain of ≈106 , a fast response time of 67µs and an ultrahigh detectivity of 6.7×1017 Jones to light signals under a low working voltage (≤0.6V). Thanks to the ultrahigh sensitivity and fast response, the device can track photoplethysmogram signals and peripheral oxygen saturation under ambient light and even provide contactless remote sensing, offering a low-power and convenient way for continuous vital signs monitoring. This work offers a novel strategy for realizing high-performance flexible PDs that are promising for low-power, user-friendly and wearable optoelectronics.

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.

Printable and flexible photodetectors via scalable fabrication for reading applications

Printing techniques have been widely adopted in the fabrication of flexible electronic components. However, its application is still limited in complex control and communication circuitry due to the low performance and low fabrication uniformity amongst printed devices, compared to conventional electronics. Thus, the electronic systems in real-world applications are hybrid integrations of printed and conventional electronics. Here we demonstrate a low-cost, low-complexity, fully-printable flexible photodetector that can withstand over 100 1 mm-radius bending cycles using a simple and scalable two-step fabrication process. The prototypes are implemented in an augmented book system to automatically detect the ambient light through optical apertures on paper of a printed book, and then transmit the information to an adjunct device. This technique demonstrates the utility of low-cost materials and processes for robust large area sensing applications and could act as a gateway to pertinent multimedia information.

Anchoring Cs4PbBr6 Crystals to PbSe Nanocrystals for the Fabrication of UV/VIS/NIR Photodetectors Using Halide Surface Chemistry

AbstractNanocrystal (NC)‐in‐matrix solids are currently attracting considerable research attention in the fields of materials science and engineering owing to their unique optoelectronic characteristics and high stability. However, the interaction between the NC surface and the matrix has been veiled and induces interface defect states that degrade the performance of photovoltaics. In this study, the effect of halide ligands on the formation of a Cs4PbBr6 (CPB) crystal matrix by determining the surfaces of PbSe NCs is investigated. The surface of the PbSe NCs is passivated with halide ions (Cl−, Br−, or I−), and the CPB crystal matrix is formed via PbBr2/CsBr treatment onto the PbSe NCs. The effects of different halide ions on the nucleation/growth of the CPB matrix are examined by chemical, structural, and optical analyses. It is found that each halide ligand has a distinct effect not only on the anchoring of CPB but also on its carrier transport mechanisms. To characterize the electronic properties of the NC matrix, its carrier mobility, photoresponsivity, and stability are measured using field‐effect transistors. Consequently, it is demonstrated that more densely passivated PbSe NCs form a higher‐quality CPB matrix. Using a NC matrix, ultraviolet‐/visible‐/near‐infrared‐active flexible photodetectors are achieved.

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.

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.

Development of novel flexible photodetectors based on 0.5PVA/0.5PVP/Fe:NiO nanocomposite system with enhanced optoelectronic properties

Ordinary casting technique has been used to fabricate the intrinsic films of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) polymer blend matrix incorporated with dissimilar weight percent contents of Fe:NiO nanocomposite (NC). X-ray diffraction (XRD) and infrared (IR) spectroscopy has been implemented to analyze NC structure of these films. Significant interaction and tuning of PVA/PVP blend matrix due to Fe:NiO NC is detected. XRD pattern reflects the structural modification and partial crystalline nature of the pristine blend matrix. The corresponding peaks of Fourier transform IR identifies the vibrational group of the synthesized samples. Atomic force microscope images indicate that a change in the Fe:NiO concentration in a pristine blend leads to an increase in the roughness and clusters. Numerous optical factors such as E g (transition band gap), refractive index (n), and E ed (absorption edge) of pure blend and blend films with different concentrations of Fe:NiO were assessed via UV–Vis optical absorption spectra. As we increased the doping concentration in pristine blends, the value of E g goes to decrease. The dispersion (E d) and oscillator (E o) energies were calculated from Wemple and Di. Domenico of a single oscillator. Although, optical susceptibilities and nonlinear refractive index were enhanced by doping with Fe:NiO NC. The change in doping content leads to modifications in the optical limiting. The photocurrent density–voltage properties of the present polymers were studied at different values of white light intensity. It was found that the photoconductivity of the PVA/PVP blend is 1.03275 × 10−8 (Ω cm)−1, while NC films varied in the range (1.03–10.6954) × 10−8 (Ω cm)−1 at 8600 lux. In addition, the photosensitivity increased from 13.82 to 24.08. The recombination process was found monomolecular process for pure and doped polymers. The present films assume the possibility of their uses in optical and photo-electric devices.