High Photocurrent Research Articles

Strain-Enhanced Large-Area Monolayer MoS2 Photodetectors.

In this study, we show a direct correlation between the applied mechanical strain and an increase in monolayer MoS2 photoresponsivity. This shows that tensile strain can improve the efficiency of monolayer MoS2 photodetectors. The observed high photocurrent and extended response time in our devices are indicative that devices are predominantly governed by photogating mechanisms, which become more prominent with applied tensile strain. Furthermore, we have demonstrated that a nonencapsulated MoS2 monolayer can be used in strain-based devices for many cycles and extensive periods of time, showing endurance under ambient conditions without loss of functionality. Such robustness emphasizes the potential of MoS2 for further functionalization and utilization of different flexible sensors.

Preparation of vertical structure SnS2/SnSe2/H–TiO2 ternary heterojunction and its high performance ultraviolet/visible photodetector

Developing highly efficient heterojunction photodetector, especially ternary heterojunctions of vertical structure, is a promising strategy to enhance the migration of photo-generated electron for exploit potentialities of optoelectronic devices. In this study, we successfully deposited two-dimensional layered SnSe2 NSs and SnS2 NSs vertically on TiO2 NTs arrays using chemical vapor deposition (CVD), constructing a novel ternary SnS2/SnSe2/H–TiO2 heterojunction. The morphology, structure, and composition of the samples were analyzed, and highly sensitive ultraviolet/visible light photodetectors were fabricated. Photocurrent measurements demonstrated that the prepared SnS2/SnSe2/H–TiO2 ternary heterojunction exhibited superior light detection capability at different wavelengths (370 nm, 450 nm, 520 nm) compared to the pristine H–TiO2 and its binary heterojunctions (SnS2/H–TiO2, SnSe2/H–TiO2). Under a bias voltage of 1 V and 370 nm illumination, it achieved a high photocurrent of 7.45 mA cm−2, a switch ratio of 7.924, as well as high responsivity (9.39 A/W), high EQE (3.15 × 103 %), and large detectivity (9.53 × 1010 Jones). The excellent performance of the SnS2/SnSe2/H–TiO2 ternary heterojunction reveals its enormous potential in the development of wide-band, high-performance photodetectors.

Design of a Novel Green Algae‐Based Biological Photovoltaic Cell with High Photocurrent and a Photoelectrochemical Biosensing Approach Utilizing the BPV for Pesticide Analysis in Water

AbstractIn this research, a green alga (Paulschulziapseudovolvox sp.) based biological photovoltaic cell (BPV) was designed. This clean energy‐friendly BPV produced photocurrent as a result of illuminating the photoanode and cathode electrodes immersed in the aqueous medium with solar energy. For this purpose, both electrodes were first coated with conductive polymers with aniline functional groups on gold electrodes. In the cell, the photoanode was first coated with a gold‐modified poly 4‐(2,5‐di(thiophen‐2‐yl)‐1H‐pyrrol‐1‐yl)benzamine polymer, (P(SNS‐NH2)). Cytochrome C (Cyt. C) material was used to provide crosslink formation with bis‐aniline covalent bonds with the conductive polymer using electrochemical techniques. Paulschulziapseudovolvox sp., one of the green algae that can convert light energy into chemical energy, is attached to this layered electrode surface. The cathode of the cell is attached to the gold electrode surface with poly 4‐(4HDithieno[3,2‐b : 2′,3′‐d]pyrrole‐4‐yl)aniline (P(DTP‐Aryl‐Amine)). Then, the bilirubin oxidase enzyme was immobilized on this film surface with glutaraldehyde activation. This cell, which can use light thanks to green algae, oxidizes and splits water, and oxygen is obtained at the photoanode electrode. At the cathode electrode, the oxygen gas is reduced to water by the bio‐electro‐catalytic method. To obtain high photocurrent from the BPV, necessary electrochemical and chemical optimizations were made during the design of the system to increase the amount of electrons that were transferred and fasten its transfer rate. While the photocurrent value generated by the designed BPV in optimum conditions and in the pseudo‐steady state is 10 mA/m2, the maximum power value obtained is 46.5 mW/m2. In addition to the production of the green algae‐based BPV generating highly efficient electricity which is the main of target of this study, some studies have also been carried out to show whether this system can be used as a pesticide biosensor. Atrazine and diuron biosensing via the BPV system was analytically characterized and recovery and interference studies related to pesticide biosensor property of the BPV were also investigated.

Dissolution-Induced Surface Reconstruction of Ni0.95Pt0.05Si/p-Si Photocathode for Efficient Photoelectrochemical H2 Production.

Metal silicide/Si photoelectrodes have demonstrated significant potential for application in photoelectrochemical (PEC) water splitting to produce H2. To achieve an efficient and economical hydrogen evolution reaction (HER), a paramount consideration lies in attaining exceptional catalytic activity on the metal silicide surface with minimal use of noble metals. Here, this study presents the design and construction of a novel Ni0.95Pt0.05Si/p-Si photocathode. Dopant segregation is used to achieve a Schottky barrier height as high as 1.0eV and a high photovoltage of 420mV. To achieve superior electrocatalytic activity for HER, a dissolution-induced surface reconstruction (SR) strategy is proposed to in situ convert surface Ni0.95Pt0.05Si to highly active Pt2Si. The resulting SR Ni0.95Pt0.05Si/p-Si photocathode exhibits excellent HER performance with an onset potential of 0.45V (vs RHE) and a high maximum photocurrent density of 40.5mAcm-2 and a remarkable applied bias photon-to-current efficiency (ABPE) of 5.3% under simulated AM 1.5 (100mWcm-2) illumination. The anti-corrosion silicide layer effectively protects Si, ensuring excellent stability of the SR Ni0.95Pt0.05Si/p-Si photoelectrode. This study highlights the potential for achieving efficient PEC HER using bimetallic silicide/Si photocathodes with reduced Pt consumption, offering an auspicious perspective for the cost-effective conversion of solar energy to chemical energy.

Preparation of Langmuir-Blodgett composite films based on sericin protein and silk fibroin with good surface-enhanced Raman scattering and photovoltaic properties

In this work, the self-assembled films of sericin protein (SP), silk fibroin (SF), and dye molecules were prepared by the Langmuir-Blodgett (LB) technique. Surface-enhanced Raman scattering (SERS) experiments demonstrated that the SP/saffron T (ST)-80 and SF/ST-60 composite LB films exhibited good Raman enhancement characteristics with enhancement factors (EFs) of 5.74×104 and 7.05×104, respectively. The relative standard deviations (RSDs) of Raman intensity were 7.19% and 18.40%, respectively, confirming the uniformity of the composite LB films. Furthermore, photoelectric conversion efficiencies indicate that the electrodes fabricated from SP/ST and SF/ST film electrodes have high carrier rates and good photocurrent generation properties. This study provides novel insights into the fabrication of multifunctional SP/dye and SF/dye composite LB films, demonstrating their potential applications in SERS and photovoltaic conversion.

Bifunctional g-GaN/Si9C15 S-scheme heterojunction for efficient photocatalytic hydrogen evolution and photodetector

S-scheme heterojunctions are commonly applied in optoelectronic devices and photocatalytic materials to achieve effective charge separation and enhance photocatalytic activity. In this study, the electronic, optical, and electrical behaviors as well as the photocatalytic water splitting performance of the g-GaN/Si9C15 S-scheme heterojunction have been researched using first-principles. The results suggest that the g-GaN/Si9C15 heterojunction is energetically, thermally, and dynamically stable. The g-GaN/Si9C15 heterojunction belongs to the S-scheme photocatalyst with the g-GaN as the oxidant and the Si9C15 as the reductant, and its band edge positions cross the standard water oxidation and reduction potentials. The g-GaN/Si9C15 heterojunction has a power conversion efficiency of 11.03 % and a large carrier mobility of 20.98 × 103 cm2 V−1 s−1. The small overpotential of 0.076 V is favorable for the occurrence of the hydrogen evolution reaction, and the oxygen evolution reaction of the g-GaN/Si9C15 heterojunction can spontaneously proceed when U = 1.23 V. The g-GaN/Si9C15 heterojunction exhibits a large solar-to-hydrogen efficiency of 25.58 %. Moreover, the g-GaN/Si9C15 heterojunction has a high photocurrent and a large extinction ratio. In conclusion, the g-GaN/Si9C15 heterojunction holds potential applications in photocatalytic water splitting and photodetector.

Photoelectrochemical Sensor for H2S Based on a Lead-Free Perovskite/Metal-Organic Framework Composite.

Halide perovskites have emerged as a highly promising class of photoelectric materials. However, the application of lead-based perovskites has been hindered by their toxicity and relatively weak stability. In this work, a composite material comprising a lead-free perovskite cesium copper iodide (CsCu2I3) nanocrystal and a metal-organic framework (MOF-801) has been synthesized through an in situ growth approach. The resulting composite material, denoted as CsCu2I3/MOF-801, demonstrates outstanding stability and exceptional optoelectronic characteristics. MOF-801 may serve a dual role by acting as a protective barrier between CsCu2I3 nanocrystals and the external environment, as well as promoting the efficient transfer of photogenerated charge carriers, thereby mitigating their recombination. Consequently, CsCu2I3/MOF-801 demonstrates its utility by providing both stability and a notably high initial photocurrent. Leveraging the inherent reactivity between H2S and the composite material, which results in the formation of Cu2S and structural alteration, an exceptionally sensitive photoelectrochemical sensor for H2S detection has been designed. This sensor exhibits a linear detection range spanning from 0.005 to 100 μM with a remarkable detection limit of 1.67 nM, rendering it highly suitable for precise quantification of H2S in rat brains. This eco-friendly sensor significantly broadens the application horizon of perovskite materials and lays a robust foundation for their future commercialization.

Hydrogen-Induced Reduction Improves the Photoelectrocatalytic Performance of Titania.

One of the main challenges to expand the use of titanium dioxide (titania) as a photocatalyst is related to its large band gap energy and the lack of an atomic scale description of the reduction mechanisms that may tailor the photocatalytic properties. We show that rutile TiO2 single crystals annealed in the presence of atomic hydrogen experience a strong reduction and structural rearrangement, yielding a material that exhibits enhanced light absorption, which extends from the ultraviolet to the near-infrared (NIR) spectral range, and improved photoelectrocatalytic performance. We demonstrate that both magnitudes behave oppositely: heavy/mild plasma reduction treatments lead to large/negligible spectral absorption changes and poor/enhanced (×10) photoelectrocatalytic performance, as judged from the higher photocurrent. To correlate the photoelectrochemical performance with the atomic and chemical structures of the hydrogen-reduced materials, we have modeled the process with in situ scanning tunneling microscopy measurements, which allow us to determine the initial stages of oxygen desorption and the desorption/diffusion of Ti atoms from the surface. This multiscale study opens a door toward improved materials for diverse applications such as more efficient rutile TiO2-based photoelectrocatalysts, green photothermal absorbers for solar energy applications, or NIR-sensing materials.

Fast Electrodeposition of MXene/PDA Composites for High‐Performance Bioelectronic Interfaces: An In Vitro Evaluation

AbstractBioelectrode is critical to many biomedical researches. However, traditional materials (typically noble metals) and manufacturing techniques limit the large‐scale production of bioelectrodes. Herein, a fast electrochemical approach is proposed to deposit versatile MXene/polydopamine (PDA) composites on a metalized substrate. PDA coating can improve the adhesion between MXene and the substrate, while MXene provides rough surfaces with unique micro/nanostructure and outstanding electrical/optical/thermal performance. The impedance of the as‐prepared bioelectrode at 1 kHz is down to 8.48 Ω cm2. The corresponding cathodic charge storage capacity (CSCc) and charge injection capacity (CIC) are up to ≈250 and 6.59 mC cm−2 respectively, much superior to that of bare Pt and other conventional material‐based electrodes. The MXene/PDA composites also demonstrate robust stability under continuous electrostimulation for 1 × 108 pulse cycles and 1000 CV cycles. Moreover, MXene/PDA composites show a high and rapid photothermal response. Photoelectrochemical activity is also observed with high photocurrent, ≈40 folds larger than that of bare Pt. The utility of this new electrode in ascorbic acid sensing is demonstrated. Excellent biocompatibility is verified via neuron adhesion test and viability assay.

Optimal Selection for Redox Couples and Enhanced Performance through Magnetic Nanofluid Electrolyte in Solar Flow Batteries

The limited photoelectric conversion efficiency poses one of the critical constraints on commercializing solar flow batteries (SFBs). This study compares the chemical and photoelectrochemical properties of three commonly used redox couples. Additionally, magnetic Fe3O4 nanoparticles, for the first time, are introduced to optimize the electrolyte, and they are compared with the original electrolyte. Across different redox couples, the variations in semiconductor flat-band potentials and carrier concentrations result in changes in photoelectric current density. Notably, FeCl2/FeCl3 redox coupled with TiO2 photoelectrodes exhibits the highest photoelectric current density, reaching 75.7 µA cm−2. However, the trade-off of this electrolyte, i.e., providing high photocurrent while being unable to supply sufficient open-circuit voltage, imposes limitations on the practical application of SFBs. Alternatively, for TEMPO and 4-OH-TEMPO electrolytes, which can provide a higher open-circuit voltage, the electrochemical activity is enhanced, and the solution ohmic resistance is reduced by introducing magnetic nanoparticles to form a magnetic nanofluid. As a result, the photoanode’s photocurrent density increases by 36.6% and 17.0%, respectively, in the two electrolytes. The work reported here effectively addresses the current issue of low photocurrent density in SFBs and presents new optimization strategies for SFBs.

High-quality dense ZnO thin films: work function and photo/electrochemical properties

Compact ZnO (wurtzite) thin films are prepared on four different substrates by (i) spray pyrolysis or (ii) pulsed reactive magnetron sputtering combined with a radio frequency electron cyclotron wave resonance plasma. Films are characterized by AFM, XRD, Kelvin probe, cyclic voltammetry, electrochemical impedance spectroscopy, and UV photoelectrochemistry. Film morphologies, defect concentrations, crystallite size, and orientation provided specific fingerprints for the electronic structure of ZnO close to the conduction band minimum. Fabricated films are referenced, if relevant, to a model system based on a wurtzite single crystal with either Zn-face or O-face termination. Kelvin probe measurements of the ZnO/air interface distinguished effects of annealing and UV excitation, which are attributed to removal of oxygen vacancies close to the surface. In turn, the work function, at the electrochemical interface, specifically addressed the growth protocol of the ZnO electrodes but not the effects of crystallinity and annealing. Finally, high photocurrents of water oxidation are observed exclusively on virgin films. This effect is then discussed in terms of photocorrosion, and work function changes due to UV light.Graphical

Performance-enhanced intrinsic polarization-sensitive organic photodetectors by molecular interaction modulation

Polarization-sensitive organic photodetectors (OPDs) are increasingly paid attention for their broad application prospect. However, it is extremely difficult to achieve highly sensitive detection of polarized light for most organic semiconductor polymers with intrinsic isotropic amorphous behavior. In this study, the performance-enhanced intrinsic anisotropic all-polymer bulk heterojunctions (BHJs) are obtained by constructing molecular fluorination engineering in the fused-ring backbone of the acceptor polymer. The molecular orientation, alignment, and packing can be effectively optimized during the floating-film formation process without using any additives and post-treatments. The outstanding intrinsic polarization-sensitive photodetection performance with a very high photocurrent dichroic ratio of 3.73, a specific detectivity of 1.3 × 1011 Jones at 0 V, and a broad linear dynamic range of 120 dB is achieved for the optimum-fluorine-content self-assembly all-polymer organic BHJ film. The superiorities of self-powered capability, fast response, and high-contrast imaging demonstrate that the backbone fluorination for acceptor polymers is conducive to achieving excellent structural regularity and can endow the intrinsic polarization-sensitive all-polymer OPDs with more demanding polarized-light detection ability.

Efficient synthesis of 3D ZnO nanostructures on ITO surfaces for enhanced photoelectrochemical water splitting

New photoactive materials with uniform and well-defined morphologies were developed for efficient and sustainable photoelectrochemical (PEC) water splitting and hydrogen production. The investigation is focused on hydrothermal deposition of zinc oxide (ZnO) onto indium tin oxide (ITO) conductive surfaces and optimization of hydrothermal temperature for growing uniform sized 3D ZnO morphologies. Fine-tuning of hydrothermal temperature enhanced the scalability, efficiency, and performance of ZnO-decorated ITO electrodes used in PEC water splitting. Under UV light irradiation and using eco-friendly low-cost hydrothermal process in the presence of stable ZnO offered uniform 3D ZnO, which exhibited a high photocurrent of 0.6 mA/cm2 having stability up to 5 h under light-on and light-off conditions. The impact of hydrothermal temperature on the morphological properties of the deposited ZnO and its subsequent performance in PEC water splitting was investigated. The work contributes to advancement of scalable and efficient fabrication technique for developing energy converting photoactive materials.

A Self-Powered Broadband Photodetector with High Photocurrent Based on Ferroelectric Thin Film Using Energy Band Structure Design

Self-powered photodetectors have the advantages of high sensitivity, sustainability, and small size and have become a research hotspot in advanced optoelectronic systems. However, the low output photocurrent density seriously hinders the practical application of ferroelectric self-powered photodetectors. Herein, the high-efficiency photoelectric detection performance of the Bi1-xHoxFeO3 ferroelectric self-powered photodetector is realized by doping Ho. The responsivity (R) and detectivity (D*) can reach 0.0159 A/W and 1.94 × 1011 Jones under monochromatic light with a wavelength of 900 nm. Meanwhile, the R and D* can reach 0.022 A/W and 2.65 × 1011 Jones under sunlight. These excellent photodetection performances are attributed to the high short-circuit current density (Jsc). When the Ho content is 6%, the output photocurrent reaches up to 0.81 mA/cm2. The systematic structure and photo-electric characteristic analysis suggest that the decrease in the band gap leads to the generation of a larger photocurrent while the ferroelectric polarization is reduced slightly. This work provides a new way to obtain high-performance self-powered photodetectors.

Efficient Acidic Photoelectrochemical Water Splitting Enabled by Ru Single Atoms Anchored on Hematite Photoanodes.

Photoelectrochemical (PEC) water splitting in acidic media holds promise as an efficient approach to renewable hydrogen production. However, the development of highly active and stable photoanodes under acidic conditions remains a significant challenge. Herein, we demonstrate the remarkable water oxidation performance of Ru single atom decorated hematite (Fe2O3) photoanodes, resulting in a high photocurrent of 1.42 mA cm-2 at 1.23 VRHE under acidic conditions. Comprehensive experimental and theoretical investigations shed light on the mechanisms underlying the superior activity of the Ru-decorated photoanode. The presence of single Ru atoms enhances the separation and transfer of photogenerated carriers, facilitating efficient water oxidation kinetics on the Fe2O3 surface. This is achieved by creating additional energy levels within the Fe2O3 bandgap and optimizing the free adsorption energy of intermediates. These modifications effectively lower the energy barrier of the rate-determining step for water splitting, thereby promoting efficient PEC hydrogen production.

An MSM photodetector based on an InGaO/TiO2 heterojunction for high-performance UV detection

As typical metal–oxide wide bandgap semiconductor devices, ultraviolet (UV) photodetectors (PDs) based on TiO2 have encountered challenges related to high dark current and low photo-to-dark suppression ratio. In this study, indium (In) was doped into Ga2O3 to create the compound InGaO (IGO). Subsequently, IGO was combined with TiO2 to fabricate IGO/TiO2 heterojunction (ITH) MSM UVPDs. The built-in electric field constructed at the contact interface is capable of depleting the majority carriers in dark and limiting the dark current. The Au interdigital electrodes and the IGO film of the top layer will form an Ohmic contact without the carrier transport barrier to construct a photoconductive device with high photo currents. The results show that the ITH UVPDs exhibit a notable photo current of 1.21 mA and a low dark current of 0.29 nA, leading to an ultrahigh photo-to-dark current ratio of 6 orders of magnitude (4.17 × 106). Additionally, the UVPDs demonstrate a significant responsivity (R) of 1.16 × 104 A/W and a remarkable detectivity (D*) of 7.34 × 1015 Jones under 290 nm UV illumination at 5 V bias. This study provides a potential method for fabricating high-performance UVPDs.

A high-performance TiO2 protective layer derived from non-high vacuum technology for a Si-based photocathode to enhance photoelectrochemical water splitting

A non-high vacuum technique was used to fabricate a TiO2 protective layer of a Si-based photocathode, in which MOF derivatives enhance carrier transfer efficiency. The photocathode has high onset potential, high photocurrent and long-term stability.

Synergistic effect of Ag@CN with BiVO4 in a unique Z-type heterojunction for enhancing photoelectrochemical water splitting performance.

In the realm of photoelectrochemical technology, the enhancement of photogenerated charge carrier separation is pivotal for the advancement of energy conversion performance. Carbon nitride (CN) is established as a photocatalytic material with significant potential and exhibits unique advantages in addressing the issue of rapid recombination of photogenerated carriers. This study utilized an efficient in situ doping method that combined Mo,W-doped BiVO4 (Mo,W:BVO) with silver-loaded CN (Ag@CN), yielding an all-solid-state Mo,W:BVO/Ag@CN heterostructure that effectively augments the separation efficiency of electron-hole pairs. Through the annealing process, Ag@CN was uniformly coated within the Mo,W:BVO thin film, significantly enlarging the interface contact area to enhance visible light absorption and photogenerated carrier movement. The results of the photoelectrochemical tests showed that the Mo,W:BVO/Ag@CN heterostructure had the highest photocurrent and charge transfer efficiency, which were 6.4 times and 3.6 times higher respectively than those of the unmodified Mo,W:BVO. Our research elucidates the interactions within all-solid-state Z-scheme heterojunctions, outlining strategic approaches for crafting innovative and superior photocatalytic systems.

Stability and photocurrent enhancement of photodetectors by using core/shell structured CsPbBr3/TiO2 quantum dots and 2D materials.

Ultra-stable CsPbBr3 perovskite quantum dots (QDs) were prepared, and the performance of the photodetector fabricated from them was enhanced by 2D material incorporation. This multi-component photodetector appears to have good stability in the ambient utilization environment. All inorganic CsPbBr3 QDs are potential candidates for application in photodetection devices. However, QDs have several issues such as defects on the QD surface, degradation under environmental conditions, and unfavorable carrier mobility limiting the high performance of the photodetectors. This work addresses these issues by fabricating a core/shell structure and introducing 2D materials (MXenes, Ti3C2Tx) into the device. Here, three types of photodetectors with QDs only, QDs with a core/shell structure, and QDs with a core/shell structure and MXenes are fabricated for systematic study. The CsPbBr3/TiO2 photodetector demonstrated a two times photocurrent enhancement compared to bare QDs and had good device stability after TiO2 shell coating. After introducing Ti3C2Tx into CsPbBr3/TiO2, a significant photocurrent enhancement from nanoampere (nA) to microampere (μA) was observed, revealing that MXenes can improve the photoelectric response of perovskite materials significantly. Higher photocurrent can avoid signal interference from environmental noise for better practical feasibility. This study provides a systematic understanding of the photocurrent conversion of perovskite quantum dots that is beneficial in advancing optoelectronic device integration, especially for flexible wearable device applications.

Development of an automated SILAR method for the sustainable fabrication of BiOI/TiO2 photoanodes.

BiOI is a promising material for use in photoelectrocatalytic water oxidation, renowned for its chemical inertness and safety in aqueous media. For device integration, BiOI must be fabricated into films. Considering future industrial applications, automated production is essential. However, current BiOI film production methods lack automation and efficiency. To address this, a continuous automated process is introduced in this study, named AutoDrop, for producing BiOI films. Autodrop results to be a fast and facile method for producing BiOI photoelectrodes. Nanostructured thin films of this layered material are prepared using a syringe pump to dispense the precursor solution onto a continuously spinning substrate. These films are integrated into a multilayered photoelectrode, featuring mesoporous TiO2 as an electron-transporting layer on top of FTO glass. In testing the photoelectrochemical performance of the BiOI/TiO2 photoelectrodes, the highest photocurrent (44 μA cm-2) is found for a heterojunction with a BiOI thickness of 320 nm. Additionally, a further protective TiO2 ultrathin layer in contact with BiOI, grown by atomic layer deposition, enhances the durability and efficiency of the photoanode, resulting in a more than two-fold improvement in photocurrent after 2 hours of continuous operation. This study advances the automation in the sustainable production of photoelectrode films and provides inspiration for further developments in the field.