Photoactive Materials Research Articles

Energy-efficient low-power LED-mediated effective photodegradation of cationic and anionic dyes by phthalocyanine-based COF sensitized ZnO photoactive material

The present work involves the synthesis of 2D covalent organic framework involving zinc phthalocyanine and perylene systems (2DZnPc) as low-power LED visible-light sensitizer for ZnO nanomaterial. The synthesized materials and their composites (2DZnPc@ZnO) were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Solid-state diffuse reflectance spectrophotometer to understand the structure, size, morphology, and optical properties. To examine the photodegradation competence of ZnO alone and its four different composites (2DZnPc@ZnO5, 2DZnPc@ZnO10, 2DZnPc@ZnO15, and 2DZnPc@ZnO20) in the presence of the energy-efficient low-power white LED (16 W) as source of visible light, and as modular pollutants, cationic methylene violet (MV) and anionic Eosin Y (EY) dyes were employed. The effect of different parameters on photocatalytic activity such as photocatalyst dosage, interaction time, pH of dye solution, and photocatalyst re-usage is examined. The results indicate that photosensitizing ZnO with 2DZnPc improved photocatalytic performance for the photodegradation of MV and EY dyes substantially. In an optimized environment, the removal efficiency of MV and EY was found to be 98 and 92 % respectively in 90 min.

Design and optimization of the performance of PbS quantum dot based vertical photodetector

Abstract Quantum dots (QDS) are widely used as photoactive materials for various optoelectronic applications, such as light-emitting diodes, photodetectors, lasers, and solar cells, because of their unique and outstanding physical properties for fabricating devices via solution-processing techniques and for varying the sizes of QD to modulate the band gap. In this study, we constructed a numerical model of a vertical photodetector using lead sulfide (PbS) quantum dot layer undergoing ligand exchange treatment with tetrabutylammonium iodide (TBAI) as the light absorption layer to obtain an optimized high-performance photodetector using 1D-Solar Cell Capacitance Simulator (SCAPS) software. For the hole transport layer (HTL) and electron transport layer (ETL), a PbS quantum dot layer that employs an ethanedithiol (EDT) ligand exchange scheme and a zinc oxide (ZnO) layer were utilized, respectively, with gold (Au) and indium tin oxide (ITO) as the bottom and upper electrodes, respectively. After optimizing the thickness and doping concentration of the absorption layer, we obtained a maximum responsivity of 0.4675 A W−1 and detectivity of 2.44 * 10 13 Jones at a reverse bias of 0.5 volts after optimizing of thickness and doping concentration of absorption layer showing an improvement of 19% and 87.7% respectively compared to the initial structure whose parameters originated from studies of PbS quantum dot solar cells with the same structure and materials, although optimization of other transport layers do not provide as great performance enhancement as absorption layer. This study demonstrates that the structural parameters of solar cells are not always applicable to photodetectors, and that photodetectors have great potential for numerical optimization. Ethical Compliance: All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Spatiotemporal Visualization of Photogenerated Carriers on an Avalanche Photodiode Surface Using Ultrafast Scanning Electron Microscopy

The spatiotemporal evolution of photogenerated charge carriers on surfaces and at interfaces of photoactive materials is an important issue for understanding fundamental physical processes in optoelectronic devices and advanced materials. Conventional optical probe-based microscopes that provide indirect information about the dynamic behavior of photogenerated carriers are inherently limited by their poor spatial resolution and large penetration depth. Herein, we develop an ultrafast scanning electron microscope (USEM) with a planar emitter. The photoelectrons per pulse in this USEM can be two orders of magnitude higher than that of a tip emitter, allowing the capture of high-resolution spatiotemporal images. We used the contrast change of the USEM to examine the dynamic nature of surface carriers in an InGaAs/InP avalanche photodiode (APD) after femtosecond laser excitation. It was observed that the photogenerated carriers showed notable longitudinal drift, lateral diffusion, and carrier recombination associated with the presence of photovoltaic potential at the surface. This work demonstrates an in situ multiphysics USEM platform with the capability to stroboscopically record carrier dynamics in space and time.

A Three-Dimensional Non-Fullerene Acceptor with Contorted Hexabenzocoronene and Perylenediimide for Organic Solar Cells.

Although fullerene derivatives such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC61BM/PC71BM) have dominated the the photoactive acceptor materials in bulk heterojunction organic solar cells (OSCs) for decades, they have several drawbacks such as weak absorption, limited structural tunability, prone to aggregation, and high costs of production. Constructing non-fullerene small molecules with three-dimensional (3D) molecular geometry is one of the strategies to replace fullerenes in OSCs. In this study, a 3D molecule, contorted hexa-cata-hexabenzocoronene tetra perylenediimide (HBC-4-PDI), was designed and synthesized. HBC-4-PDI shows a wide and strong light absorption in the whole UV-vis region as well as suitable energy levels as an acceptor for OSCs. More importantly, the 3D construction effectively reduced the self-aggregation of c-HBC, leading to an appropriate scale phase separation of the blend film morphology in OSCs. A preliminary power conversion efficiency of 2.70 % with a champion open-circuit voltage of 1.06 V was obtained in OSCs with HBC-4-PDI as the acceptor, which was the highest among the previously reported OSCs based on c-HBC derivatives. The results indicated that HBC-4-PDI may serve as a good non-fullerene acceptor for OSCs.

Oxygen vacancy induction strategy to regulate the evolution of valence- and free-electrons for boosting visible photodegradation of tetracycline hydrochloride

The generation, migration and reaction paths of electrons are the key steps for photodegradation of pollutants. However, efficient operation of the above pathways is still challenging. Herein, by strong coordination and slow pyrolysis, we constructed a narrow band Zn-Mn bimetallic photoactive core-shell material (Mn@Zn-N-C, Eg = 3.38 eV) with abundant oxygen vacancies for enhancing the above electronic paths. The photodegradation experiments of tetracycline hydrochloride (TCH) showed that the formation and transfer of vacancy-induced free electrons in the synthesized Mn@Zn-N-C was the key to improve the photocatalytic activity. The DFT calculation results revealed that the photogenerated electrons can transfer along the Mn-O-Zn bridge in Mn@Zn-N-C, and promote the formation of MnIV, which directly capture the free electrons and reset itself to MnII site. In this case, the introduction of Mn would enhance the separation of h+ and e-. The adjacent vacancies and defects then also trapped the above free electrons and hinder the recombination of photogenerated carriers. Simultaneously, the localized valence electron transfer between the above redox pairs (Mn4+/Mn2+ and Zn2+/Zn0) also promoted the long-term stability of the photocatalytic process. In summary, using vacancy induction strategy to regulate the evolution of valence- and free-electrons is a promising method to improve the production-transfer-utilization efficiency of photogenerated carriers.

MXene-Enhanced Bi2S3/CdIn2S4 Heterojunction Photosensitive Gate for DEHP Detection in a Signal-On OPECT Aptamer Biosensor.

Organic electrochemical transistors with signal amplification and good stability are expected to play a more important role in the detection of environmental pollutants. However, the bias voltage at the gate may have an effect on the activity of vulnerable biomolecules. In this work, a novel organic photoelectrochemical transistor (OPECT) aptamer biosensor was developed for di(2-ethylhexyl) phthalate (DEHP) detection by combining photoelectrochemical analysis with an organic electrochemical transistor, where MXene/Bi2S3/CdIn2S4 was employed as a photoactive material, target-dependent DNA hybridization chain reaction was used as a signal amplification unit, and Ru(NH3)63+ was selected as a signal enhancement molecule. The poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-based OPECT biosensor modulated by the MXene/Bi2S3/CdIn2S4 photosensitive material achieved a high current gain of nearly a thousand times at zero bias voltage. The developed signal-on OPECT sensing platform realized sensitive and specific detection of DEHP, with a detection range of 1-200 pM and a minimum detection limit of 0.24 pM under optimized experimental conditions, and its application to real water samples was also evaluated with satisfactory results. Hence, the construction of this OPECT biosensing platform not only provides a promising tool for the detection of DEHP but also reveals the great potential of the OPECT application for the detection of other environmental toxins.

Morphological modulation enabled by non‐halogenated solvent‐processed simple solid additives for high‐efficiency organic solar cells

AbstractThe simple‐structural and volatile solid additive 1,4‐dibromobenzene (DBrB) can outperform organic solar cells (OSCs) fabricated with 1,4‐diiodobenzene and 1,4‐dichlorobenzene in terms of power conversion efficiency (PCE). A remarkable PCE of 17.0% has been achieved in a binary OSC based on DBrB‐optimized photoactive materials processed from non‐halogenated solvents, which is mainly attributed to the formation of a three‐dimensional interpenetrating network and the orderly arrangement of the photoactive materials by improving the intermolecular interaction. This optimized morphology enables efficient charge transfer/transport as well as suppressed charge recombination, resulting in the simultaneous increase in all photovoltaic parameters. More importantly, we demonstrate that non‐halogenated solvent‐processed DBrB enabled PM6:Y6‐HU OSCs with an impressive PCE of 18.6%, which is the highest efficiency yet reported for binary OSCs. This study suggests that the novel DBrB volatile solid additive is an effective approach to optimizing the morphology and thereby improves the photovoltaic performance of OSCs.image

Recent Progress in Photoelectrochemical Sensing of Pesticides in Food and Environmental Samples: Photoactive Materials and Signaling Mechanisms.

Pesticides have become an integral part of modern agricultural practices, but their widespread use poses a significant threat to human health. As such, there is a pressing need to develop effective methods for detecting pesticides in food and environmental samples. Traditional chromatography methods and common rapid detection methods cannot satisfy accuracy, portability, long storage time, and solution stability at the same time. In recent years, photoelectrochemical (PEC) sensing technology has gained attention as a promising approach for detecting various pesticides due to its salient advantages, including high sensitivity, low cost, simple operation, fast response, and easy miniaturization, thus becoming a competitive candidate for real-time and on-site monitoring of pesticide levels. This review provides an overview of the recent advancements in PEC methods for pesticide detection and their applications in ensuring food and environmental safety, with a focus on the categories of photoactive materials, from single semiconductor to semiconductor-semiconductor heterojunction, and signaling mechanisms of PEC sensing platforms, including oxidation of pesticides, steric hindrance, generation/decrease in sacrificial agents, and introduction/release of photoactive materials. Additionally, this review will offer insights into future prospects and confrontations, thereby contributing novel perspectives to this evolving domain.

High performance photoelectrochemical immunosensing platform based on front-illuminated Mo:BiVO4 photoelectrodes for procalcitonin assay

The outstanding photoactive materials are the imperative for the construction of a front-illuminated photoelectrochemical (PEC) biosensor, which is crucial step for improving the detection sensitivity. Yet, the weak and unstable initial PEC signals of the photoelectrodes have limited evidently the detection performance. Herein, a front-illuminated “on-off” PEC immunosensor was constructed based on Mo:BiVO4 as photoactive matrix and Au/CeO2 as signal quencher for sensitive detection of procalcitonin (PCT). Systematic studies reveal that the Mo doped BiVO4 can increase the charge carrier density of BiVO4, leading to much higher initial signal under front illumination than back illumination. Moreover, Mo:BiVO4 was directly grown on conducting substrates, which effectively overcomes the loose combination of sensing substrate ensuring good electrical contact and continuity. Upon coupling with Au/CeO2 as signal quencher, the initial photocurrent signal can be significantly quenched. As a result, the proposed PEC immunosensor presents a wide linear range from 10 fg mL−1 to 50 ng mL−1 with a detection limit of 2.45 fg mL−1. Impressively, this study will open a new avenue for the construction of highly efficient and stable photoelectrode, as well as extend the application of PEC biosensor for biomarkers detection in early disease diagnosis.

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.

Simple π-Conjugated Polymers Based on Bithiazole for Nonfullerene Organic Photovoltaics.

Thiazole, as a family of five-membered heteroaromatic rings, is an interesting building unit that can play a role in coplanarizing the backbone as well as deepening the HOMO energy level, which is beneficial for the design of π-conjugated polymers for the photoactive materials in organic photovoltaics (OPVs). Here, we designed and synthesized π-conjugated polymers with simple chemical structures, which consist of 2,2'-bithiazole or 5,5'-bithiazole and alkylthiophenes as the polymer backbone. In fact, the polymers can be easily synthesized in much fewer steps compared to the typical high-performance polymers based on fused heteroaromatic rings. Interestingly, PTN5 exhibited a markedly higher ordered structure than PTN2. This was likely ascribed to the more coplanar and rigid backbone of PTN5 than that of PTN2 originating in the effectively arranged S···N interaction. As a result, the nonfullerene photovoltaic cell based on PTN5 showed a PCE of 12.2%, which was much higher than the cell based on PTN2 (4.3%) and was high for the polymers consisting of only nonfused rings. These results demonstrate that thiazole-based polymers are promising photoactive materials for OPVs and emphasize the importance of careful molecular design utilizing noncovalent interactions.

A signal polarity conversion photoelectrochemical immunosensor for neuron-specific enolase detection based on MgIn2S4-sensitized CsPbBr3.

Aphotoelectrochemical (PEC) immunosensor was designed based on MgIn2S4-decorated inorganic halide perovskite CsPbBr3 combined with the signal polarity conversion strategy for neuron-specific enolase (NSE) detection. CsPbBr3 was applied as the basic photoactive material owing to its excellent optical and electronic properties, which provide a good PEC performance for sensor construction. In order to improve the stability of this perovskite, the three-dimensional flower-like MgIn2S4 with a desirable direct band gap was applied to enhance the PEC response. Also, the excellent structure of MgIn2S4 provides large surface-active sites for CsPbBr3 loaded. For enhancing the detection sensitivity of PEC immunosensor, p-type CuInS2 was used as a signal probe which fixed on detection antibody (Ab2). When the target NSE was present, the photogenerated electrons produced by CuInS2 were transferred to the test solution, and the polarity of PEC signal changes. Based on the above photosensitive materials and signal conversion strategy, the proposed PEC immunosensor showed favorable detection performance, and the lineardetection range is 0.0001 ~ 100ng/mL with a 38fg/mL of detection limit. The proposed strategy improved the adhibition of CsPbBr3 in the analytical chemistry field as well as provided a reference method for other protein detections.

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.

Understanding photochemical degradation mechanisms in photoactive layer materials for organic solar cells.

Over the past decades, the field of organic solar cells (OSCs) has witnessed a significant evolution in materials chemistry, which has resulted in a remarkable enhancement of device performance, achieving efficiencies of over 19%. The photoactive layer materials in OSCs play a crucial role in light absorption, charge generation, transport and stability. To facilitate the scale-up of OSCs, it is imperative to address the photostability of these electron acceptor and donor materials, as their photochemical degradation process remains a challenge during the photo-to-electric conversion. In this review, we present an overview of the development of electron acceptor and donor materials, emphasizing the crucial aspects of their chemical stability behavior that are linked to the photostability of OSCs. Throughout each section, we highlight the photochemical degradation pathways for electron acceptor and donor materials, and their link to device degradation. We also discuss the existing interdisciplinary challenges and obstacles that impede the development of photostable materials. Finally, we offer insights into strategies aimed at enhancing photochemical stability and discuss future directions for developing photostable photo-active layers, facilitating the commercialization of OSCs.

Digital multimeter-based portable photoelectrochemical immunoassay with enzyme-catalyzed precipitation for screening carbohydrate antigen 125.

The degree of the carbohydrate antigen 125 (CA-125) level in serum is positively correlated with the severity of ovarian cancer. In this study, a facile photoelectrochemical (PEC) immunoassay was devised for sensitive detection of CA-125 employing enzyme-catalyzed precipitation to weaken the photocurrent of hollow porous In2O3 nanotubes incorporating CdS nanoparticles. Upon the addition of the target analyte, horseradish peroxidase (HRP) enriches as a result of the formation of the sandwich immunocomplex, which can catalyze the conversion of 4-chloro1-naphthol (4-CN) to benzo-4-chlorohexadienone (4-CD) employing H2O2 as a cofactor. The as-produced insoluble precipitate acts as an obstacle to hinder the absorption of visible light by photoactive materials, thereby resulting in a decrease in photocurrent. Moreover, the weakened signal can be easily read out by a digital multimeter (DMM), advancing the convenience of the detection system. The preliminary analysis data indicate that the PEC immunoassay shows an efficient response to CA-125 levels ranging from 0.1 to 100 U mL-1 with a limit of detection (LOD) as low as 0.046 U mL-1 (S/N = 3). Most importantly, the proposed portable method has shown satisfactory performance in terms of selectivity, reproducibility, stability, and analysis in complex biological matrices.

Green solvent-processed organic solar cells based on a small-molecule Ir(iii) complex as electron donor materials

Through the synergistic involvement of an environmentally friendly solvent and high temperature spin-coating process, the power conversion efficiency for small-molecule Ir(iii) complex based organic solar cells could be significantly improved.

Recent advances in photoelectrochemical platforms based on porous materials for environmental pollutant detection.

Human health and ecology are seriously threatened by harmful environmental contaminants. It is essential to develop efficient and simple methods for their detection. Environmental pollutants can be detected using photoelectrochemical (PEC) detection technologies. The key ingredient in the PEC sensing system is the photoactive material. Due to the unique characteristics, such as a large surface area, enhanced exposure of active sites, and effective mass capture and diffusion, porous materials have been regarded as ideal sensing materials for the construction of PEC sensors. Extensive efforts have been devoted to the development and modification of PEC sensors based on porous materials. However, a review of the relationship between detection performance and the structure of porous materials is still lacking. In this work, we present an overview of PEC sensors based on porous materials. A number of typical porous materials are introduced separately, and their applications in PEC detection of different types of environmental pollutants are also discussed. More importantly, special attention has been paid to how the porous material's structure affects aspects like sensitivity, selectivity, and detection limits of the associated PEC sensor. In addition, future research perspectives in the area of PEC sensors based on porous materials are presented.

A cerium-doped tungsten trioxide-functionalized sensing platform for photoelectrochemical detection of ascorbic acid with high sensitivity.

A highly efficient photoelectrochemical (PEC) strategy was proposed for the determination of ascorbic acid (AA). Cerium-doped tungsten trioxide (Ce-WO3) microrods were synthesized by a hydrothermal method and further characterized through transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. Thereafter, they were deposited onto a cleaned fluorine-doped tin oxide (FTO) glass forming the working electrode as the photoactive material. Under strong visible light irradiation, the resulting PEC sensing platform generated the corresponding electron-hole pairs, converting light signals into electrical signals. Ascorbic acid served as a good electron donor to trap holes for improvement of photocurrent responses on Ce-WO3/FTO. Besides, the strength of photocurrent signals versus the logarithm of ascorbic acid concentration showed a good linearity over the ascorbic acid concentration range of 100-4000 nM and the limit of detection (LOD) was estimated to be 28.6 nM. Importantly, this PEC sensor had a fast response, high sensitivity, and distinguished selectivity for detecting ascorbic acid. In addition, it also had the features of being simple to fabricate, low production cost, and portable, which made it a promising means of ascorbic acid determination.

Recent Advancements in Light-responsive Supercapacitors

Abstract: With so many of our daily activities related to electricity, from telecommunication to laptops and computers, the use of electric energy has skyrocketed in today's technology-based world. Energy output must rise to meet rising energy demand. Still, as fossil fuels are running out, we must turn to more renewable energy sources, particularly solar energy, which can be harnessed and converted to electricity by solar-powered cells. The issues, however, are brought about by the sunlight's unpredictable energy output. The energy produced by solar cells should therefore be stored using energy storage technologies. This notion led to the development of the photo-supercapacitor, a device that combines a solar cell with a supercapacitor to store the energy generated by the solar cells. However, recently researchers developed light-responsive materials for supercapacitors that could be used directly as electrode materials and deposited on various transparent and conductive substrates. Such light-responsive supercapacitors could be operated directly by shining solar light without using any solar cell. A light-responsive supercapacitor's efficiency is primarily influenced by the active materials used in its electrode fabrication. The main components of high-energy conversion, which improves a light-responsive supercapacitor's performance and shelf life, are photoactive materials, counter electrodes, compatible electrolytes, and transparent substrate performances. Furthermore, light-responsive supercapacitors are cutting-edge and promising energy storage devices that can self-charge under light illumination by converting light to electrical energy and storing it for later use. They are considered a novel approach to energy issues in electrical transportation, electronic equipment, and on-chip energy storage devices. Thus, this review paper opens up an avenue for the direct utilization of photoactive nanomaterials for electrochemical energy storage and demonstrates the substantial potential for the fabrication of advanced light-responsive supercapacitors. This study also covers the fundamentals of how this exciting field works, the historical trajectory of how far it has come, and the promising prospects for its future.

Photoelectrochemical immunoassay for the breast cancer biomarker CA 15-3 based on In2O3/ZnIn2S4 heterojunctions

A split-type photoelectrochemical immunoassay was designed to detect CA 15-3 using In2O3/ZnIn2S4 heterojunctions as the photoactive materials.