Organic Photovoltaic Stability: Understanding the Role of Engineering Exciton and Charge Carrier Dynamics from Recent Progress.

Benefiting from the synergistic development of material design, device engineering, and the mechanistic understanding of device physics, the certified power conversion efficiencies (PCEs) of single-junction non-fullerene organic solar cells (OSCs) have already reached a very high value of exceeding 19%. However, in addition to PCEs, the poor stability is now a challenging obstacle for commercial applications of organic photovoltaics (OPVs). Herein, recent progress made in exploring operational mechanisms, anomalous photoelectric behaviors, and improving long-term stability in non-fullerene OSCs are highlighted from a novel and previously largely undiscussed perspective of engineering exciton and charge carrier pathways. Considering the intrinsic connection among multiple temporal-scale photocarrier dynamics, multi-length scale morphologies, and photovoltaic performance in OPVs, this review delineates and establishes a comprehensive and in-depth property-function relationship for evaluating the actual device stability. Moreover, this review has also provided some valuable photophysical insights into employing the advanced characterization techniques such as transient absorption spectroscopy and time-resolved fluorescence imagings. Finally, some of the remaining major challenges related to this topic are proposed toward the further advances of enhancing long-term operational stability in non-fullerene OSCs.

Recent Advances in Black Phosphorous-Based Photocatalysts for Degradation of Emerging Contaminants.

The recalcitrant nature of emerging contaminants (ECs) in aquatic environments necessitates the development of effective strategies for their remediation, given the considerable impacts they pose on both human health and the delicate balance of the ecosystem. Semiconductor-based photocatalytic technology is recognized for its dual benefits in effectively addressing both ECs and energy-related challenges simultaneously. Among the plethora of photocatalysts, black phosphorus (BP) stands as a promising nonmetallic candidate, offering a host of advantages including its tunable direct band gap, broad-spectrum light absorption capabilities, and exceptional charge mobility. Nevertheless, pristine BP frequently underperforms, primarily due to issues related to its limited ambient stability and the rapid recombination of photogenerated electron-hole pairs. To overcome these challenges, substantial research efforts have been devoted to the creation of BP-based photocatalysts in recent years. However, there is a noticeable absence of reviews regarding the advancement of BP-based materials for the degradation of ECs in aqueous solutions. Therefore, to fill this gap, a comprehensive review is undertaken. In this review, we first present an in-depth examination of the fabrication processes for bulk BP and BP nanosheets (BPNS). The review conducts a thorough analysis and comparison of the merits and limitations inherent in each method, thereby delineating the most auspicious avenues for future research. Then, in line with the pathways followed by photogenerated electron-hole pairs at the interface, BP-based photocatalysts are systematically categorized into heterojunctions (Type I, Type II, Z-scheme, and S-scheme) and hybrids, and their photocatalytic performances against various ECs and the corresponding degradation mechanisms are comprehensively summarized. Finally, this review presents personal insights into the prospective avenues for advancing the field of BP-based photocatalysts for ECs remediation.

Multiple-Time Scale Exciton Dynamics in Organic Photovoltaic Devices.

Organic photovoltaics (OPVs) are regarded as one of the most promising candidates for various outdoor and indoor application scenarios. The development and application of nonfullerene acceptors have pushed power conversion efficiencies (PCEs) of single-junction cells to exceed 19%, and values approaching 20% are within sight. This progress has resulted in some unexpected photophysical observations deserving more in-depth spectroscopic research. In this Perspective, we have summarized recent photophysical advances in accordance with results of ultrafast spectroscopy in our and other groups and provide our point of view on multiple-time scale exciton dynamics involving the following aspects: long-range exciton diffusion driven by dual Förster resonance energy transfer, origins of driving force for hole transfer under small energy offsets, trap-induced charge recombination in outdoor and indoor OPVs, and a picture of real-time evolution of excitons and charge carriers regarding stability. Moreover, our understanding of the photophysical property-function relationship is proposed in state-of-the-art OPVs. Finally, we point out the remaining challenges devoted to the further development of versatile OPVs.

Microplastic sink that cannot be ignored in chemosynthetic organisms.

Marine microplastic (MP) pollution is a widespread concern; however, to date, MP pollution in chemoautotrophic ecosystems remains largely unknown. This study focuses on the cold seep in the South China Sea. Two dominant species, namely mussel (Gigantidas platifrons) and squat lobster (Shinkaia crosnieri), were collected for examining the MP pollution. MPs were present in both mussels and squat lobsters with abundances of 0.13 ± 0.04 and 0.17 ± 0.06 items/ind., respectively. MPs were mainly fibrous (62.5 %) and transparent (45.8 %). The main polymer type was polyester (54.2 %). About 86.5 MPs/m2 were found inhabiting mussels and squat lobsters-a value comparable to those reported in benthos. This pilot report on MP pollution in cold-seep species provides key information for studies on MP pollution in chemoautotrophic ecosystems and evidence regarding a potential biological MP sink. The role of cold-seep organisms in MP retention and transport in the regional sea merits further attention.

Microplastic load of benthic fauna in Jiaozhou Bay, China.

The prevalence of microplastic pollution in the ocean has caused widespread concern. Many studies have focused on the occurrence of microplastics in the marine environment and organisms, but the fate of microplastics in the ocean is still unclear, and the factors affecting the distribution of microplastics have not yet been consistently concluded. The aims of this study were to estimate the load of microplastics in benthic organisms as a temporary storage and to analyze the factors affecting microplastic ingestion by benthic organisms. For the purpose of this study, the benthic organisms in Jiaozhou Bay, China, were collected quarterly and were divided into the following six groups: polychaetes, mollusks, crustaceans, echinoderms, fish, and others. We concluded that the microplastic abundance in the benthos in Jiaozhou Bay was 1.00 ± 0.11 items/ind. (15.5 ± 3.5 items/g). The total load of microplastics in the benthic fauna in the bay with an area of 374 km2 was estimated to be 36.4 kg. On an individual basis, the fish contained significantly more microplastics than the other taxa. Furthermore, the characteristics of the microplastics in the benthic organisms were mainly fibrous, black, polyethylene, and <500 µm in size. In addition, the microplastic ingestion by benthic organisms was regulated by multiple factors, including biological characteristics and the environment. The masses of the organisms, the ambient seawater and sediment, and the spatial variations all influenced the microplastic ingestion by the organisms. The results of this study demonstrate that benthic organisms are an important storage for microplastics as they transferred through the ocean, and they provide an unbiased comparison of microplastic pollution among multiple organisms and the relevant pollution factors.

Fluorination of Terminal Groups Promoting Electron Transfer in Small Molecular Acceptors of Bulk Heterojunction Films.

The fluorination strategy is one of the most efficient and popular molecular modification methods to develop new materials for organic photovoltaic (OPV) cells. For OPV materials, it is a broad agreement that fluorination can reduce the energy level and change the morphology of active layers. To explore the effect of fluorination on small molecule acceptors, we selected two non-fullerene acceptors (NFA) based bulk heterojunction (BHJ) films, involving PM6:Y6 and PM6:Y5 as model systems. The electron mobilities of the PM6:Y5 and PM6:Y6 BHJ films are 5.76 × 10-7 cm2V-1s-1 and 5.02 × 10-5 cm2V-1s-1 from the space-charge-limited current (SCLC) measurements. Through molecular dynamics (MD) simulation, it is observed that halogen bonds can be formed between Y6 dimers, which can provide external channels for electron carrier transfer. Meanwhile, the "A-to-A" type J-aggregates are more likely to be generated between Y6 molecules, and the π-π stacking can be also enhanced, thus increasing the charge transfer rate and electron mobility between Y6 molecules.

Reducing Voltage Losses of Organic Solar Cells against Energetics Modifications by Thermal Stress.

Voltage losses are one of the main obstacles for further improvement in the power conversion efficiency of organic solar cells. In this work, we investigate the effect of thermal stress on voltage losses in various material systems by multiple spectroscopic measurements on both devices and thin films. The energetics of nonfullerene small molecules are more readily altered under thermal stress compared to all-polymer and fullerene-based systems, thereby strongly affecting open-circuit voltage. These energetics variations correlate with the glass transition of respective materials. While nonfullerene small molecular acceptor systems exhibit both dynamic and static disorders which can be restrained in annealed films, all-polymeric systems exhibit dominated static disorders, which are also stable against thermal stress. The much higher voltage losses in fullerene-based systems compared to the other two counterparts are mainly due to the losses from device band gap to charge transfer states and the high nonradiative recombination.

Genome-wide identification of growth-regulating factor transcription factor family related to leaf and stem development in alfalfa.

Growth-regulating factors (GRFs) play crucial roles in plant growth and stress response. To date, there have been no reports of the analysis and identification of the GRF transcription factor family in alfalfa. In this study, we identified 27 GRF family members from alfalfa (Medicago sativa L.) "Xinjiang Daye", and analyzed their physicochemical properties. Based on phylogenetic analysis, these MsGRFs were divided into five subgroups, each with a similar gene structure and conserved motifs. MsGRFs genes are distributed on 23 chromosomes, and all contain QLQ and WRC conserved domains. The results of the collinearity analysis showed that all MsGRFs are involved in gene duplication, including multiple whole-genome duplication or segmental duplication and a set of tandem duplication, indicating that large-scale duplication is important for the expansion of the GRF family in alfalfa. Several hormone-related and stress-related cis-acting elements have been found in the promoter regions of MsGRFs. Some MsGRFs were highly expressed in young leaves and stems, and their expression decreased during development. In addition, the leaf size of different varieties was found to vary, and MsGRF1 to 4, MsGRF18 to 20, and MsGRF22 to 23 were differentially expressed in large and small leaf alfalfa varieties, suggesting that they are critical in the regulation of leaf size. The results of this study can benefit further exploration of the regulatory functions of MsGRFs in growth and development, and can identify candidate genes that control leaf size development.

Comprehensive transcriptomic and metabolomic profiling reveals the differences between alfalfa sprouts germinated with or without light exposure.

Alfalfa sprouts are among the most nutritionally rich foods, and light exposure is a critical factor in determining their biomass and quality. However, detailed metabolic and molecular differences between yellow and green alfalfa sprouts remain unclear. In this study, comprehensive metabolomic and transcriptomic analyses were integrated to evaluate the nutrient composition of alfalfa sprouts during germination with or without light exposure. Differentially expressed genes and differentially accumulated metabolites in green and yellow alfalfa sprouts were significantly enriched in secondary metabolic pathways, such as the isoflavonoid biosynthesis pathway. Green alfalfa sprouts contained a wide variety of lipids, flavonoids, phenolic acids, and terpenoids, among which the top three upregulated were calycosin, methyl gallate, and epicatechin 3-gallate, whereas yellow alfalfa sprouts contained relatively more isoquercitrin. These results provide new insights into the nutritional value and composition of alfalfa sprouts under different germination regimes.

Transcriptome Analysis of Leaf Senescence Regulation Under Alkaline Stress in Medicago truncatula.

In plants, the leaf is an essential photosynthetic organ, and is the primary harvest in forage crops such as alfalfa (Medicago sativa). Premature leaf senescence caused by environmental stress can result in significant yield loss and quality reduction. Therefore, the stay-green trait is important for improving the economic value of forage crops. Alkaline stress can severely damage leaf cells and, consequently, cause leaf senescence. To understand the molecular regulatory mechanisms and identify vital senescence-associated genes under alkaline stress, we used high-throughput sequencing to study transcriptional changes in Medicago truncatula, a model plant for forage crops. We identified 2,165 differentially expressed genes, 985 of which were identical to those in the dark-induced leaf senescence group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that the 985 genes were mainly enriched in nutrient cycling processes such as cellular amino acid metabolic processes and organic substance catabolic processes, indicating nutrient redistribution. The other 1,180 differentially expressed genes were significantly enriched in the oxidoreductase complex, aerobic respiration, and ion transport. Our analysis showed the two gene sets guiding the coupled physiological and biochemical alterations play different roles under alkaline stress with a coordinated and integrated way. Many transcription factor families were identified from these differentially expressed genes, including MYB, WRKY, bHLH, and NAC which have particular preference involved in stress resistance and regulation of senescence. Our results contribute to the exploration of the molecular regulatory mechanisms of leaf senescence in M. truncatula under alkaline stress and provide new candidate genes for future breeding to improve the biomass and quality of forage crops.

Reproducibility in Time and Space-The Molecular Weight Effects of Polymeric Materials in Organic Photovoltaic Devices.

The reproducibility issue is one of the major challenges for the commercialization of large-area organic electronic devices. It involves both the device-to-device variation and opto-electronic properties in different positions of a single thin film. Herein, the molecular weight effects in polymeric semiconductors with three widely used photovoltaic donor materials P3HT, PBDB-T, and PM6 are systematically investigated. A simple but effective method is proposed to evaluate the uniformity of large-area devices by adopting the micron-level grid electrodes in organic thin films. An interesting phenomenon is observed that the device is gradually improved uniformly with the Mw range lower than 100 kg mol-1 . In neat films, both the mobility and energetic disorder values of hole carriers exhibit relatively lower coefficient of variation (cv ) in high molecular-weight systems. After blending with the electron-accepting materials, their bulk heterojunction films also enjoy more uniform hole transfer rates, fluorescence lifetimes, and power conversion efficiencies in single and different devices. This work not only proposes a facile approach to evaluate the electrical properties of large-area organic thin films, but also demonstrates the relationship between molecular weight and device reproducibility in polymer solar cells. This contribution provides a new insight into the commercial large-scale production of organic electronics.

Synergistic Effect of Chiral Nanofibers Amplifying the Orbit Angular Momentum To Enhance Optomagnetic Coupling.

Manipulating magnetic bits by photon in spintronics, opto-magnetic coupling, is lagging far behind what we could expect. To investigate the issue, one should face the problem to find photon dependence of spin dynamics and spin manipulation. In this work, through introducing chiral orbit in organic crystals, circularly polarized photon can manipulate spin via the channel of photon-orbit-spin interactions. Under the stimulus of the magnetic field, strong spin polarization will feed back to the change in polarized state of light. Moreover, twisting several chiral nanofibers into a thick one, a more pronounced opto-magnetic coupling is clearly observed due to the chirality generated larger chiral orbit. Meanwhile, spin dynamics (or spin response times) inside the aggregated thick chiral fiber can be further tuned by circularly polarized light. Hopefully, this study can deepen the understanding of organic chiral spin-photonics and enhance the application of organic functional crystals in the future.

Visible-light-driven photocatalytic disinfection by S-scheme α-Fe2O3/g-C3N4 heterojunction: Bactericidal performance and mechanism insight.

High-performance photocatalytic applications require to develop heterostructures between two semiconductors with matched band energy levels to facilitate charge-carrier separation. The S-scheme photocatalytic system has great potential to be explored, in terms of the improvement of charge separation, however, small efforts have been made in photocatalytic disinfection application. In this study, a non-toxic and low-cost S-scheme photocatalytic system composed of α-Fe2O3 and g-C3N4 was fabricated by in-suit production of g-C3N4 and firstly applied into water disinfection. The α-Fe2O3/g-C3N4 junction demonstrated an enhanced activity for photocatalytic bacterial inactivation, with the complete inactivation of 7 log10 cfu·mL-1 of Escherichia coli K-12 cells within 120 min under visible light irradiation. Its logarithmic bacterial inactivation efficiency was nearly 7 times better than that of single g-C3N4. The experimental results suggested that the effective prevention of charge-carrier recombination led to an improved generation of reactive oxygen species (ROSs), resulting in impressive disinfection performance. Moreover, the DNA gel electrophoresis experiments validated the reason for the irreversible death of bacteria, which was the leakage and destruction of chromosomal DNA. In addition, this S-scheme heterojunction also showed excellent photocatalytic disinfection performance in authentic water matrices (including tap water, secondary treated sewage effluent, and surface water) under visible light irradiation. Hence, the α-Fe2O3/g-C3N4 composite has great potential for sustainable and efficient photocatalytic disinfection applications.

Preparation of metal-free BP/CN photocatalyst with enhanced ability for photocatalytic tetracycline degradation.

The successful application of photocatalysis in practical water treatment opreations relies greatly on the development of highly efficient, stable and low-cost photocatalysts. The low-cost metal-free photocatalyst made up of black phosphorus (BP) and graphitic carbon nitride (CN) was successfully constructed and firstly used for the photocatalytic treatment of antibiotic contaminants in this work. Compared with bare CN, the BP/CN photocatalyst exhibited the enhanced photocatalytic performance for tetracycline hydrochloride (HTC) degradation, that 99% of HTC was removed by 6BP/CN (doping amount of BP was 6%) within 30 min under the simulated visible-light irradiation. The efficiency was even comparable to those of some high-efficiency photocatalysts recently-reported such as Fe0@POCN, CuInS2/Bi2MoO6 and Cu2O@HKUST-1. Under natural sunlight illumination, the determined apparent rate constant for degradation of HTC by BP/CN was 2.7 times as that by P25 TiO2. The experimental results indicated that loading BP on CN could enhance the separation of charge carriers and promote the ability of light absorption for visible-light, thus leading to a greater catalytic activity. Meanwhile, the influences of different operating variables (pH, water, ion and HTC concentration) on HTC degradation were studied in detail. Furthermore, the degradation pathway of HTC was also proposed. In addition, the photocatalytic activity of the BP/CN for production of hydrogen peroxide (H2O2) was also studied, which could reach up to 501.04 µmol g-1h-1. It is anticipated that BP/CN photocatalyst could be used for practical water treatment.

Deep Compressed Imaging via Optimized-Pattern Scanning.

The need for high-speed imaging in applications such as biomedicine, surveillance and consumer electronics has called for new developments of imaging systems. While the industrial effort continuously pushes the advance of silicon focal plane array image sensors, imaging through a single-pixel detector has gained significant interests thanks to the development of computational algorithms. Here, we present a new imaging modality, Deep Compressed Imaging via Optimized-Pattern Scanning (DeCIOPS), which can significantly increase the acquisition speed for a single-detector-based imaging system. We project and scan an illumination pattern across the object and collect the sampling signal with a single-pixel detector. We develop an innovative end-to-end optimized auto-encoder, using a deep neural network and compressed sensing algorithm, to optimize the illumination pattern, which allows us to reconstruct faithfully the image from a small number of samples, and with a high frame rate. Compared with the conventional switching-mask based single-pixel camera and point scanning imaging systems, our method achieves a much higher imaging speed, while retaining a similar imaging quality. We experimentally validated this imaging modality in the settings of both continuous-wave (CW) illumination and pulsed light illumination and showed high-quality image reconstructions with a high compressed sampling rate. This new compressed sensing modality could be widely applied in different imaging systems, enabling new applications which require high imaging speed.

Effect of the Energy Offset on the Charge Dynamics in Nonfullerene Organic Solar Cells.

The energy offset, considered as the driving force for charge transfer between organic molecules, has significant effects on both charge separation and charge recombination in organic solar cells. Herein, we designed material systems with gradually shifting energy offsets, including both positive and negative values. Time-resolved spectroscopy was used to monitor the charge dynamics within the bulk heterojunction. It is striking to find that there is still charge transfer and charge generation when the energy offset reached -0.10 eV (ultraviolet photoelectron spectroscopy data). This work not only indicates the feasibility of the free carrier generation and the following charge separation under the condition of a negative offset but also elucidates the relationship between the charge transfer and the energy offset in the case of polymer chlorination.

Solution-Processed Organic Solar Cells with High Open-Circuit Voltage of 1.3 V and Low Non-Radiative Voltage Loss of 0.16 V.

Compared with inorganic or perovskite solar cells, the relatively large non-radiative recombination voltage losses (ΔVnon-rad ) in organic solar cells (OSCs) limit the improvement of the open-circuit voltage (Voc ). Herein, OSCs are fabricated by adopting two pairs of D-π-A polymers (PBT1-C/PBT1-C-2Cl and PBDB-T/PBDB-T-2Cl) as electron donors and a wide-bandgap molecule BTA3 as the electron acceptor. In these blends, a charge-transfer state energy (ECT ) as high as 1.70-1.76 eV is achieved, leading to small energetic differences between the singlet excited states and charge-transfer states (ΔECT ≈ 0.1 eV). In addition, after introducing chlorine atoms into the π-bridge or the side chain of benzodithiophene (BDT) unit, electroluminescence external quantum efficiencies as high as 1.9 × 10-3 and 1.0 × 10-3 are realized in OSCs based on PBTI-C-2Cl and PBDB-T-2Cl, respectively. Their corresponding ΔVnon-rad are 0.16 and 0.17 V, which are lower than those of OSCs based on the analog polymers without a chlorine atom (0.21 and 0.24 V for PBT1-C and PBDB-T, respectively), resulting in high Voc of 1.3 V. The ΔVnon-rad of 0.16 V and Voc of 1.3 V achieved in PBT1-C-2Cl:BTA3 OSCs are thought to represent the best values for solution-processed OSCs reported in the literature so far.

Antibiotics promote abdominal fat accumulation in broilers.

Antibiotics stimulate the growth of animals but result in drug residues and bacterial resistance. In this study, the negative effect of antibiotics on abdominal fat deposition was evaluated in broilers. The results showed that adding both chlortetracycline (50 g/1,000 kg) and tylosin (50 g/1,000 kg) significantly increased abdominal fat weight, abdominal fat percentage (p < .05), and triglyceride and cholesterol levels (p < .05) in blood. Also, both products synchronously stimulated intestinal absorption and synthesis of liver fat. The expression levels of the peroxisome proliferator-activated receptor Î³ (PPARγ), diacylgycerol acyltransferase 2 (DGAT2), lipoprotein lipase (LPL), and fatty acid-binding protein (FABP4) genes in abdominal fat tissue significantly increased (p < .05 or 0.01) when antibiotics were added to the feed. However, no significant difference was found in expression of the fatty acid synthesis (FAS) or acetyl CoA carboxylase (ACC) genes. Further in vitro study results revealed that antibiotics had no effect on fat content or the related gene expression levels in preadipocytes. In summary, the antibiotics induced fat deposition in adipose tissues by activating extracellular absorption of fatty acids from intestinal absorption and synthesis of liver fat. However, it shows no direct regulation by adipose tissue.

Identification of the Differentially Expressed Genes of Muscle Growth and Intramuscular Fat Metabolism in the Development Stage of Yellow Broilers.

High-quality chicken meat is an important source of animal protein for humans. Gene expression profiles in breast muscle tissue were determined, aiming to explore the common regulatory genes relevant to muscle and intramuscular fat (IMF) during the developmental stage in chickens. Results show that breast muscle weight (BMW), breast meat percentage (BMP, %), and IMF (%) continuously increased with development. A total of 256 common differentially expressed genes (DEGs) during the developmental stage were screened. Among them, some genes related to muscle fiber hypertrophy were upregulated (e.g., CSRP3, LMOD2, MUSTN1, MYBPC1), but others (e.g., ACTC1, MYL1, MYL4) were downregulated from Week 3 to Week 18. During this period, expression of some DEGs related to the cells cycle (e.g., CCNB3, CCNE2, CDC20, MCM2) changed in a way that genetically suggests possible inhibitory regulation on cells number. In addition, DEGs associated with energy metabolism (e.g., ACOT9, CETP, LPIN1, DGAT2, RBP7, FBP1, PHKA1) were found to regulate IMF deposition. Our data identified and provide new insights into the common regulatory genes related to muscle growth, cell proliferation, and energy metabolism at the developmental stage in chickens.