High Photoresponsivity Research Articles

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

Ag2O/β-Ga2O3 Heterojunction-Based Self-Powered Solar Blind Photodetector with High Responsivity and Stability.

Self-powered deep-ultraviolet photodetectors have received considerable attention in recent years because of their efficiency, reliability, and various applications in civilian and military fields. Herein, a Ag/Ag2O layer is continuously deposited on a β-Ga2O3 epitaxial layer by a facing target sputtering system without opening the chamber, which has an advantage in time and cost. A p-n junction photodetector was constructed through the Ag2O/β-Ga2O3 heterojunction and by varying the thickness of the Ag film, which was controlled by the sputtering time. The effect of top electrode thickness on the photoresponse characteristics of photodetectors was studied. Because thin Ag films have low surface roughness, indicating low optical loss and good interfacial conditions, photodetectors using a thin Ag film as the top electrode exhibit high photoresponsivity. However, Ag films that were thinner than the threshold thickness, which is the minimum thickness required to form a continuous, homogeneous surface film, exhibited rather low performance owing to the high reflection and scattering caused by the inhomogeneous surface morphology. The as-fabricated photodetector with a 20 nm Ag film presents a high on/off ratio of 3.43 × 108, responsivity and detectivity of 25.65 mA/W and 6.10 × 1011 Jones, respectively, and comparable rise and decay times of 108 and 80 ms, respectively. Additionally, even after three months of storage in an ambient environment, the photoresponse of the photodetector was maintained, indicating good stability in air. These results suggest that Ag2O/β-Ga2O3 heterojunction-based photodetectors with thin Ag films can be used in various applications requiring deep-ultraviolet detection without an external power supply.

Hybrid Nanocomposites of All‐Inorganic Halide Perovskites with Polymers for High‐Performance Field‐Effect‐Transistor‐Based Photodetectors: An Experimental and Simulation Study

AbstractAll‐inorganic halide perovskites have recently emerged as a promising candidate for new‐generation optoelectronics. The device performance of solution‐processed photodetectors critically depends on the surface morphology and film features, however, the behind mechanism is not clear till now. In this paper, a feasible method for surface‐passivating all‐inorganic halide perovskites with poly(3‐hexylthiophene) (P3HT) as the photoactive layer for field‐effect transistor (FET)‐based photodetectors is presented, and the underlying mechanisms to enhance device performance are investigated by experimental and simulating study. As the result, a high photoresponsivity of 469 A W−1 with a specific detectivity of 1.34 × 1014 Jones is obtained under 0.4 mW cm−2 405 nm illumination for FET‐based photodetector Au(S&D)/CsPbBr3:P3HT/PMMA/Al(G). This experimental and simulating study shows that the enhanced‐performance origins from improving the photogenerated charge carriers transportation and suppressing the dark current through the photodetectors.

Si/SnSe-Nanorod Heterojunction with Ultrafast Infrared Detection Enabled by Manipulating Photo-Induced Thermoelectric Behavior.

Photothermal detectors have attracted tremendous research interest in uncooled infrared imaging technology but with a relatively slow response. Here, Si/SnSe-nanorod (Si/SnSe-NR) heterojunctions are fabricated as a photothermal detector to realize high-performance infrared response beyond the bandgap limitation. Vertically standing SnSe-NR arrays are deposited on Si by a sputtering method. Through manipulating the photoinduced thermoelectric (PTE) behavior along the c-axis, the Si/SnSe-NRs heterojunction exhibits a unique four-stage photoresponse with a high photoresponsivity of 106.3 V W-1 and high optical detectivity of 1.9 × 1010 cm Hz1/2 W-1 under 1342 nm illumination. Importantly, an ultrafast infrared photothermal response is achieved with the rise/fall time of 11.3/258.7 μs. Moreover, the coupling effect between the PTE behavior and external thermal excitation enables an improved response by 288.4%. The work not only offers a new strategy to develop high-speed photothermal detectors but also performs a deep understanding of the PTE behavior in a heterojunction system.

Selective Chemical Vapor Deposition Growth of WS2/MoS2 Vertical and Lateral Heterostructures on Gold Foils.

Vertical and lateral heterostructures consisting of atomically layered two-dimensional (2D) materials exhibit intriguing properties, such as efficient charge/energy transfer, high photoresponsivity, and enhanced photocatalytic activities. However, the controlled fabrication of vertical or lateral heterojunctions on metal substrates remains challenging. Herein, we report a facile and controllable method for selective growth of WS2/MoS2 vertical or lateral heterojunctions on polycrystalline gold (Au) foil by tuning the gas flow rate of hydrogen (H2). We find that lateral growth is favored without H2, whereas vertical growth mode can be switched on by introducing 8–10 sccm H2. In addition, the areal coverage of the WS2/MoS2 vertical heterostructures is tunable in the range of 12–25%. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) results demonstrate the quality and absence of cross-contamination of the as-grown heterostructures. Furthermore, we investigate the effects of the H2 flow rate on the morphology of the heterostructures. These pave the way to develop unprecedented 2D heterostructures towards applications in (opto)electronic devices.

High performance UV–Vis photodetectors based on tin monosulfide film synthesized by physical vapor deposition

Two-dimensional tin monosulfide (SnS) has demonstrated high absorption coefficient, narrow band gap, and superior carrier mobility, which the excellent properties make it more promising in the optoelectronic devices field. Herein, a series of 2D SnS film with different thicknesses are prepared by physical vapor deposition and the film possess high crystallinity and less defect. The SnS based photoelectrochemical photodetector has been designed, which shows the high photoresponse and fast response time in UV–Vis region. Importantly, this photodetector not only shows higher Iph (5.50 μA/cm2) and Rph (16.34 μA/W) at 0.6 V but also exhibits a self-powered photoresponse behavior even at 0 V. This study demonstrates that the PVD-grown SnS film in centimeter-scale has a great potential for high performance photoelectrochemical photodetector.

Organic Ion Template‐Guided Solution Growth of Ultrathin Bismuth Oxyselenide with Tunable Electronic Properties for Optoelectronic Applications

Abstract2D Bi2O2Se has recently attracted widespread research interest due to its high electron mobility and good air stability with tunable bandgap. However, the direct and controllable growth of large‐size, high‐quality ultrathin Bi2O2Se with tunable electronic properties remains a great challenge. Here, an organic ion template‐guided solution growth method, is developed using water as a solvent to efficiently obtain high‐quality 2D Bi2O2Se. Significantly, the thicknesses and morphologies of 2D Bi2OxSe with various oxygen deficiencies; are also achieved. Optical spectroscopic results indicate that oxygen defects can dramatically tune the electronic properties of Bi2O2Se, such as work function, band gap, and energy‐band positions. As a result, the optimized Bi2O2Se devices exhibit a high photoresponsivity of 842.91 A W−1, photo‐detectivity of 8.18 × 1012 Jones under 532 nm laser, and electron mobility of 334.7 cm2 V−1 s−1. This work proposes a new green solution method to synthesize large‐sized, high‐quality Bi2O2Se with tunable electronic structures that can be extended for various applications and provides a new possibility of transfer‐free large‐scale device manufacturing.

Broadband self-powered photoelectrochemical photodetector based on Te/Se heterostructure nanocomposites

Van der Waals (vdW) heterojunctions formed from different nanomaterials not only have the characteristics of each material but also exhibit novel physical properties due to the combination of them. In this work, we report on the facile synthesis of Te/Se heterostructure nanocomposites, and their application as a photosensitive material for photoelectrochemical (PEC)-type photodetectors. The Te/Se-based PEC-type photodetectors are found to achieve excellent photodetection performance and have a broad optical response spectrum that covers the ultraviolet (365 nm) to near-infrared (980 nm) regions. With 1.0 M KOH as the electrolyte, the Te/Se-based PEC-type photodetectors exhibit a photoresponsivity of 4.04 μA W−1, a specific detectivity of 1.6 × 107 Jones, and a fast response time of less than 0.2 s under 365 nm illumination at 0 V, indicating excellent self-powered capability. Additionally, under an applied bias potential of 0.6 V, the photodetectors exhibit a high photoresponsivity of up to 83.19 μA W−1 and a specific detectivity of 3.3 × 108 Jones. Moreover, the Te/Se-based PEC-type photodetectors show good cycle stability after loop running for 1500 s.

Strong interfacial coupling in vertical WSe2/WS2 heterostructure for high performance photodetection

Two-dimensional van der Waals (vdWs) heterostructures have shown great potential in the field of electronic and optoelectronic applications over the recent decade. However, the controlled preparation of high-quality vdWs heterostructures remains a great challenge ascribing to the incompatibility of different material synthesis processes. Here, we report a two-step chemical vapor deposition method for the growth of high quality WS2 on a WSe2 template with a very low temperature of ∼550 °C, where WO3 nanosheets formed in the first step are further employed as the precursor for synthesis of the top WS2 layer in the second step. Such low growth temperatures in the second step also enable the effective protection of bottom WSe2 during the WS2 growth process and, therefore, result in high-quality WSe2/WS2 heterostructures. Photoluminescence characterizations are further conducted, where significant interlayer exciton emission is observed, indicating strong interlayer coupling in the heterostructure. Based on the obtained WSe2/WS2 heterostructure, dual-channel photosensitive devices were further designed and systematically studied, where high photoresponsivity (3 A/W) as well as fast response speed (<1 ms) are obtained. The developed WO3-assisted growth technique would provide an effective reference for the controlled synthesis of high quality vdWs heterostructures and promote further applications in high-performance optoelectronic devices.

Self-standing polyvinyl chloride film as flexible substrate for WSe2 based photodetector

Self-standing polymer materials have gained recognition as a flexible substrate for various optoelectronic devices. Here, we incorporated polyvinyl chloride (PVC) with tungsten diselenide (WSe2) microcrystals. The WSe2 microcrystals are added to PVC by solution mixing process. The WSe2-PVC composite film possess excellent flexibility, electrical conductivity of 20 kΩsq−1 at room temperature, high photoresponsivity of 0.3310 mAW−1, detectivity of 1.527 x 109 Jones and external quantum efficiency up to 8.7%. The free-standing WSe2-PVC photodetectors show durability and reproducibility even after 7 months and show stable photoresponse in the bent state. The visible light WSe2-PVC photodetector is sensitive to different monochromatic radiations (470 nm, 540 nm and 670 nm) and demonstrates potential applications in next-generation wearable optoelectronic devices.

Weyl-Semimetal TaIrTe4/Si Nanostructures for Self-Powered Schottky Photodetectors

Weyl semimetal-based photodetectors have attracted great attention due to their high performance in fast, self-powered, and ultra-broad-band photodetection. However, the inherent large dark current of the semimetal hinders further improvement of their performance. Thus, it is urgent to utilize a van der Waals (vdW) heterojunction strategy to effectively decrease the dark current and separate the carriers. Herein, a vertical Schottky junction photodetector based on Weyl semimetal TaIrTe4 and n-Si nanostructures has been studied. The junction presents a high photoresponsivity of 910 mA W–1, a specific detectivity of ∼1.04 × 1011 jones, and a fast response speed of 15.1/18.2 μs under 808 nm irradiation. Furthermore, a stable and reproducible broad-band detection (325–2000 nm) is achieved, due to the efficient NIR light absorption of TaIrTe4. In particular, the device presents impressive responsivities of 14/1.32/0.45 mA W–1 under 1310/1550/2000 nm light, respectively. Notably, these excellent performances of the TaIrTe4/Si nanostructures are superior to those of most of the previously explored 2D materials/Si-based devices and are comparable to those of several commercial silicon photodiode sensors. It is believed that the above results can provide ideas for the research of Weyl semimetals in the application of high-performance nanoscale optoelectronic devices.

Broadband photoresponse arising from photo-bolometric effect in quasi-one-dimensional Ta2Ni3Se8

In this paper, we report the synthesis of high-quality Ta2Ni3Se8 crystals free of noble or toxic elements and the fabrication and testing of photodetectors on the wire samples. A broadband photoresponse from 405 nm to 1550 nm is observed, along with performance parameters including relatively high photoresponsivity (10 mA W−1) and specific detectivity (3.5 × 107 Jones) and comparably short response time (τ rise = 433 ms, τ decay = 372 ms) for 1064 nm, 0.5 V bias and 1.352 mW mm−2. Through extensive measurement and analysis, it is determined that the dominant mechanism for photocurrent generation is the photo-bolometric effect, which is believed to be responsible for the very broad spectral detection capability. More importantly, the pronounced response to 1310 nm and 1550 nm wavelengths manifests its promising applications in optical communications. Considering the quasi-one-dimensional structure with layered texture, the potential to build nanodevices on Ta2Ni3Se8 makes it even more important in future electronic and optoelectronic applications.

β-Ga2O3 nanowires: controlled growth, characterization, and deep-ultraviolet photodetection application

We investigate the growth of () β-Ga2O3 nanowires with a GaN seed crystal in detail. Growth of () β-Ga2O3 nanowires starts with the formation of (001) Ga(II)–O chains of octahedral Ga2O6 structures, indicating the initial formation of () and (001) atomic facets of β-Ga2O3 nanowires. Subsequent growth of Ga2O3 leads to the formation of (100) Ga(I)–O chains and energetically stable (100) and (010) sidewalls and octahedral Ga2O6 structures in the β-Ga2O3 nanowires. Energetically stable tetrahedral GaO4 structures are eventually formed in the β-Ga2O3 nanowires. High-quality N-doped () β-Ga2O3 nanowires are synthesized and growth kinetics is clarified. The β-Ga2O3 nanowires deep-ultraviolet photodetectors show superior performance with high photoresponsivity (3.5 × 103 A W−1) and detectivity (9.6 × 1015 Jones) at −10 V bias.

Fully Printed Optoelectronic Synaptic Transistors Based on Quantum Dot-Metal Oxide Semiconductor Heterojunctions.

Optoelectronic synaptic transistors with hybrid heterostructure channels have been extensively developed to construct artificial visual systems, inspired by the human visual system. However, optoelectronic transistors taking full advantages of superior optoelectronic synaptic behaviors, low-cost processes, low-power consumption, and environmental benignity remained a challenge. Herein, we report a fully printed, high-performance optoelectronic synaptic transistor based on hybrid heterostructures of heavy-metal-free InP/ZnSe core/shell quantum dots (QDs) and n-type SnO2 amorphous oxide semiconductors (AOSs). The elaborately designed heterojunction improves the separation efficiency of photoexcited charges, leading to high photoresponsivity and tunable synaptic weight changes. Under the coordinated modulation of electrical and optical modes, important biological synaptic behaviors, including excitatory postsynaptic current, short/long-term plasticity, and paired-pulse facilitation, were demonstrated with a low power consumption (∼5.6 pJ per event). The InP/ZnSe QD/SnO2 based artificial vision system illustrated a significantly improved accuracy of 91% in image recognition, compared to that of bare SnO2 based counterparts (58%). Combining the outstanding synaptic characteristics of both AOS materials and heterojunction structures, this work provides a printable, low-cost, and high-efficiency strategy to achieve advanced optoelectronic synapses for neuromorphic electronics and artificial intelligence.

Photo‐Responsive Molecular Junctions Activated by Perovskite/Graphene Heterostructure Electrode

AbstractPhotoresponsivity is a fundamental process that constitutes optoelectronic devices. In molecular junction devices, one of the most adopted strategies is to employ photoactive molecules that can undergo conformational change upon light illumination as the conduction channel. However, such devices suffer from their relatively low photoresponsivity, long switching time, and unidirectional switching. In this study, the authors employed organohalide perovskite (OHP)/graphene heterojunction as a photoactive electrode that acted a source of photo‐generated carriers collected as photocurrent in self‐assembled monolayer (SAM)‐based molecular junctions. This hybrid device architecture of perovskite/graphene/SAM allows the molecular junctions to attain a high photoresponsivity with molecules that have intrinsically little photoresponse. The authors elucidate the role of the molecular SAM in enhancing the photoresponsivity by systematically examining the transport and charge transfer processes at the graphene/SAM interface via molecules with different intrinsic dipole moments. This, corroborated with a theoretical analysis, reveals the origin of the observed photoresponsivity as light‐induced coupling between the SAM and the OHP/graphene electrode within the orbital‐mediated resonant tunnelling transport regime. These findings advance the understanding of photo‐induced charge transport in molecular junctions with heterointerfaces, providing a road‐map for designing high‐performance molecular optoelectronic devices based on hybrid device architecture.

A candidate material EuSn2As2-based terahertz direct detection and imaging

Exploring the photoelectric performance of emerging materials represented by graphene, black phosphorus and transition metal dichalcogenides is attracting enormous research interest for a wide range of electronic and photonic applications. The realization of low-power consuming photodetectors with high sensitivity and fast photoresponse in the terahertz band remains one of the profound challenges in optoelectronics. In this study, a material-EuSn2As2 has been successfully implemented to realize highly sensitive terahertz photodetectors. The non-equilibrium dynamics in a two-dimensional plane allow an optionally switching between different styles of direct photon-conversions: the analogous photoconductive and photovoltaic modes spontaneously supported by the intrinsic electronic system. The prototype devices exhibited excellent sensitivity of 0.2–1.6 A/W (0.3–2.4 kV/W) from 0.02 to 0.30 THz at room temperature, corresponding to a noise-equivalent power <30pW/Hz0.5 and a fast response time <16 μs. The versatile switching behaviour and performance of the EuSn2As2 flakes-based terahertz detectors were validated via rigorous full-dimension and imaging experiments. These results open the feasibility avenues for low-energy photoelectronic applications of EuSn2As2 material.

Comparing deep eutectic solvents and cyclodextrin complexes as curcumin vehicles for blue-light antimicrobial photodynamic therapy approaches.

Curcumin (Cur), a polyphenolic compound derived from Curcuma longa L., has garnered the attention of the scientific community due to its remarkable biological properties such as its potential as a photosensitizing agent for photodynamic therapy (PDT). However, due to its low solubility in aqueous media and instability at physiological and alkaline pH, Cur has struggled to find relevant clinical application. To tackle these shortcomings, two distinct Cur-based formulations based on either complexation with methyl-β-cyclodextrin (MβCD), MβCDC-Cur, or dissolution in a choline chloride (ChCl): glycerol (Gly) deep eutectic solvent (DES), DES-Cur, were produced, physio-chemically characterized and compared regarding their potential as phototherapeutic agents for blue-light antimicrobial photodynamic therapy (aPDT) approaches. Both MβCD-Cur and DES-Cur were able to greatly enhance Cur solubility profile when compared to Cur powder. However, MβCD-Cur appears to hinder some of Cur's basal biological properties and possessed greater basal cytotoxicity towards L929 murine fibroblast cell line. Furthermore, MβCD-Cur was less photo-responsive when exposed to light which may hamper its application in blue-light aPDT approaches. In contrast, DES-Cur showed good biological properties and high photoresponsivity, displaying relevant phototoxicity against bacterial pathogens (≥ 99.9% bacterial reduction) while being better tolerated by L929 murine cells. Overall, this study found DES to be the more effective vehicle for Cur in terms of phototherapeutic potential which will serve as basis to develop novel platforms and approaches for blue-light aPDT targeting localized superficial infections.

Microwave-assisted one-pot hydrothermal synthesis of V and La co-doped ZnO/CNTs nanocomposite for boosted photocatalytic hydrogen production

In this work, vanadium and lanthanum co-doped ZnO/CNTs (VL-ZnO/CNTs) composites of large surface area and enhanced light assimilation range were produced for boosted hydrogen evolution from water. The photocatalysts were investigated for their morphological, structural, optical and photocatalytical properties. The photocatalytic activity of the composites was evaluated in pure water and in a mixture of water and methanol under simulated sunlight and visible light illumination. Under simulated sunlight irradiation, the maximum hydrogen generation rate of 925 μmolh−1g−1 from a combination of water and methanol was attained, which is almost 7 times higher than hydrogen generation rate achieved with pure ZnO. The VL-ZnO/CNTs photocatalyst resulted in hydrogen production rate of 267 μmolh−1g−1 from the water-methanol medium when exposed to visible light. This rate was about 3.5 folds lower than that achieved under simulated sunlight illumination. This improvement in hydrogen production rate is attributed to large surface area, high photo-response, better separation/transportation of the charge carriers and synergistic impact of V, La and CNTs in the designed photocatalyst.

High-performance hybrid graphene-CsPbBr3 perovskite nanocrystals phototransistor

Integrating graphene with other highly light absorptive materials into heterostructures is of great interest to improve the optoelectronic properties of graphene based phototransistors. Here, we fabricated a hybrid graphene-CsPbBr3 nanocrystal (NCs) phototransistor using CsPbBr3 NCs with large absorption coefficient as light absorption materials and graphene with high mobility as charge transport layer. The graphene-CsPbBr3 NCs phototransistor showed high photo response performances with responsivity (R) of 0.54 A/W at the incident light irradiation (Ee) of 56 mW/cm2. Moreover, the phototransistor exhibited rapid photo response with rise/decay time of 38/58 ms. The hybrid phototransistor has great potential applications in the photodetection and multifunction optoelectronics.

Comparative study of nitrogen doped multi walled carbon nanotubes grafted with carboxy methyl cellulose hybrid composite by inverse gas chromatography and its UV photo detectors application

In this present work, the synthesis of nitrogen doped multi walled carbon nanotubes (N-MWCNTs) grafted Sodium-carboxy methyl cellulose (Na-CMC) hybrid composite was carried out via thermal reduction process. The hybrid composites were thermodynamically characterized by inverse gas chromatography (IGC) and compared to Na-CMC particles. The results were obtained by using 14 different IGC methods and models. We proved that the free energy of adsorption of the different solvents on N-MWCNTs-Na-CMC surface was equal to the summation of both free enthalpies of the solvents separately adsorbed on N-MWCNT and on Na-CMC surfaces. The London dispersive surface free energy of different materials was calculated by using the various molecular models. The more precise results were obtained by Hamieh model based on the effect of the temperature on the surface area of organic molecules. It was proved that the dispersive component of the surface energy of N-MWCNTs-Na-CMC was equal to the geometric mean than that of N-MWCNTs and Na-CMC surfaces. Lewis Acid base properties of the various materials were determined by using the different models and methods. A stronger basic character was highlighted for the different solid surfaces with more accentuated acid base character for N-MWCNT solid. Furthermore, the potential usage of the hybrid nanocomposite was studied for the practical application of the self-powered UV photodetection. On the other hand, the N-MWCNTs-Na-CMC hybrid heterostructure N-MWCNTs-Na-CMC exhibited excellent photoresponse characteristics with a good stability and reproducibility under the UV illumination (λ=382 nm) at zero bias. The high photoresponse performances were mainly attributed to the improved conductivity and enhanced charge transfer resulting from the synergetic effect of N-MWCNTs-Na-CMC hybrid heterostructure. The detailed photoresponse properties of the N-MWCNTs-Na-CMC hybrid heterostructure was discussed in detail using energy band theory.