Distribution Of Acceptors Research Articles

Native Point Defects Controlling Piezoelectric Voltage in Strained ZnO Microwires.

Piezovoltages generated by ZnO nano/microwire bending and strain enable electronic biogenerators that harvest human body movement to power-implanted biomedical devices. Currently, low voltages generated by these biogenerators limit their use to replace today's biomedical batteries. Electrically charged native point defects inside ZnO microwires can control these macroscopic piezo voltages, generating transverse electric fields that couple with strained wires' lengthwise piezoelectric fields so they redistribute spatially and change voltage output. Cathodoluminescence spectroscopy inside a scanning electron microscope correlates tip voltages directly with native point defect distributions of individual ZnO microwires in three dimensions. Spatial distributions of common CuZn antisites in ZnO extending throughout their length correlate this defect's acceptor nature and distribution directly with piezoelectric potential, revealing how they can control the tip piezovoltage of ZnO microwire-based nanogenerators, identifying specific defects to increase device output, and suggesting growth and processing treatments to create these defects.

Suppressing Static and Dynamic Disorder for High-Efficiency and Stable Thick-Film Organic Solar Cells via Synergistic Dilution Strategy.

Developing stable and highly efficient thick-film organic solar cells (OSCs) is crucial for the large-scale commercial application of organic photovoltaics. A novel synergistic dilution strategy to address this issue, using Polymethyl Methacrylate (PMMA) -modified zinc oxide (ZnO) as the interfacial layer, is introduced. This strategy effectively mitigates oxygen defects in ZnO while also regulating the self-assembly process of the active layer to achieve an ordered distribution of donors and acceptors. In synergistic diluted devices, the dynamic disorder is reduced owing to the suppression of electron-phonon coupling, while the static disorder is suppressed by improved molecular stacking and enhanced intermolecular interactions. Consequently, the 300nm PM6:L8-BO device post-synergistic dilution manifests a marked enhancement in device performance, achieving a photovoltaic power conversion efficiency (PCE) >17% with excellent thermal stability. A typical ternary system is selected to explore the general applicability of synergistic dilution strategy, the PCE has been enhanced significantly from 17.89% to 18.72%, which falls within the range of the highest values among inverted single junction OSCs. As a practical application that depends on the pivotal synergy between high efficiency and stability, this approach paves the way for large-scale implementation of OSCs and ensures cost-effectiveness.

Enhancing Detection Frequency and Reducing Noise Through Continuous Structures via Release-Controlled Transfer Toward Light-Based Wireless Communication.

Organic photodetectors (OPDs) have received considerable attention owing to their superior absorption coefficient and tunable bandgap. The introduction of bulk-heterojunction (BHJ) structure aims to maximize charge generation, however, its response speed is constrained by the random distribution of donor and acceptor. Herein, a multiple-active layer design consisting of a single acceptor layer and a bulk-heterojunction layer (A/BHJ structure) is introduced, which combines the benefits of both the planar junction and the BHJ, improving photo-sensing. A transfer process is employed for this structure, which involves calculating the energy release rate at each interface, considering temperature and velocity. Consequently, the OPD with the A/BHJ structure is successfully fabricated through transfer printing, resulting in reduced dark current, superior detectivity (1.06 × 1013 Jones), and rapid response, achieved by creating a high hole injection barrier and suppressing trap sites within the interfaces. By thoroughly investigating charge dynamics in the structure, the A/BHJ structure-based OPD attains large bandwidth detection with high signal-to-noise. An efficient wireless data communication system with digital-to-analog conversion is showcased using the A/BHJ structure-based OPD.

Enhanced chemiluminescence resonance energy transfer using surfactant-modified AIE carbon dots.

Chemiluminescence resonance energy transfer (CRET) efficiency can be enhanced by confining CRET donors and acceptors within nanoscale spaces. However, this enhanced efficiency is often affected by uncertainties stemming from the random distribution of CRET donors and acceptors in such confined environments. In this study, a novel confined nanospace was created through the surfactant modification of carbon dots (CDs) exhibiting aggregation-induced emission (AIE) characteristics. Hydrophobic CRET donors could be effectively confined within this nanospace. The distance between the CRET donors and acceptors could be controlled by anchoring the AIE-CDs as the CRET acceptors, resulting in significantly improved CRET efficiency. Furthermore, this AIE-CDs-based CRET system was successfully applied to the detection of hydrogen peroxide (H2O2) in rainwater, showcasing its potential for practical applications.

Study on trap sensitivity for single material gate and double material gate nano-ribbon FETs

In this work, the trap sensitivity of single material gate (SMG) and dual material gate (DMG) nano ribbon FETs (NRFETs) are reported using TCAD Sentaurus Device simulator. The trap sensitivity is extracted for Gaussian trap distribution of both acceptor and donor type traps. We have reported the trap sensitivity for the variation in trap concentration, energy peak position, work function of metal gate, and temperature for both the NRFETs. It is realized that trap sensitivity is greater and lesser than 100% for acceptor type trap in SMG and DMG NRFETs, respectively, whereas, such sensitivity is 147% and 123% for donor type trap concentration, respectively. Temperature also shows a significant variation in trap sensitivity for both the NRFETs. The increase in work function leads to the reduction in trap sensitivity for both NRFETs in existence of acceptor and donor trap charges. The maximum sensitivity in trap are 400% and 275% for SMG and DMG NRFETs, respectively, in presence of donor trap concentration. Moreover, the trap sensitivity is very insignificant at high gate bias for donor type trap concentration with wide variation in parameters.

Microbial communities outperform extracellular polymeric substances in the reduction of hexavalent chromium by anaerobic granular sludge

The reduction of hexavalent chromium [Cr(VI)] by microbiota agents is a potential method for ecological remediation in heavily contaminated soil. This study investigated the contribution of microbial community and extracellular polymeric substances (EPS) to reduce Cr(VI) using lab-cultured anaerobic granular sludge (AGS). The AGS demonstrated an impressive reduction efficiency of 99.3% for Cr(VI) in soil, operating within an initial Cr(VI) concentration range of 500–3000 mg/kg. The distribution of typical electron acceptors, e.g., SO42-, NO3-, and Fe3+, had a negligible influence on microbial Cr(VI) reduction. The contribution of EPS on Cr(VI) reduction accounted for only 2.1% of the total Cr(VI) reduction, implying that Cr(VI) reduction driven by AGS was primarily caused by the direct effect of microbiota. High-throughput sequencing analysis confirmed that an increasing trend in the relative abundance of Cr reduction bacteria (Sphingopyxis: 0.40–5.54%, Thermonas: 0.41–5.70%, Edaphobaculum: 0.35–6.64%, etc.), and the stability (0.716–4.114) of microbial co-occurrence networks was significantly promoted by the end of the experiment. Materials characterization indicated that successful reduction of Cr(VI) to trivalent chromium [Cr(III)] and formed in Cr(OH)3, and functional groups, O-H, N-H, -CH, and -CH2, of AGS likely played a vital role in Cr(VI) reduction. Overall, these findings offer insights into the remediation technique of microbial Cr(VI) reduction in highly-contaminated soil based on the interaction network stability of the microbial community in AGS.

Characterizing the Thickness Distribution of Donor and Acceptor in Organic Photovoltaics via Quasi‐Monochromatic Light Transmittance

AbstractThe performance of organic solar cells is sensitive to the film thickness and the uniformity of the donor and acceptor distribution in the photoactive layer. Especially, in the quasi‐planar heterojunction fabricated by layer‐by‐layer process, the donor and acceptor materials may be non‐homogeneously distributed across the entire photoactive layer. Visualization of the spatial distributions of donor and acceptor components sheds light on the relationship between nanostructures and device performances. Based on the distinct infrared absorption characteristics of the organic donor and acceptor, a quasi‐monochromatic light transmittance (QMLT) technique is proposed to quantify the donor and/or acceptor thickness in the photoactive layer blend across the entire device area with nanometer precision. The variation in thickness of donor and acceptor can be clearly and separately revealed. Accordingly, the impacts of spin coating techniques (such as dynamic or static dispensing, and on‐center or off‐center spin coating), as well as solvent choices, on film morphology and device performance can be correlated by the noncontact, nondestructive, and convenient QMLT method.

Influence of acetate-to-butyrate ratio on carbon chain elongation in anaerobic fermentation

This study investigated the effect of electron acceptor (EA) distribution (acetate to butyrate ratio) on the carbon chain elongation (CCE) process. The results showed that the higher content of butyrate in the initial material led to the higher production of caproate. The maximum production of caproate was 3.74 ± 0.30 g·L−1, which was obtained when only butyrate was added as EA. Little caproate but much butyrate was produced where only acetate was added as EA. This indicated that CCE bacteria preferentially selected acetate as the EA to produce butyrate, and butyrate could be selected as EA to produce caproate only when the acetate content was much lower than butyrate. Unclassified_f_Dysgonomonadaceae, Massilibacterium, and Seramator were the predominant bacteria. Functional enzyme analysis showed that high butyrate content strengthened the fatty acid biosynthesis pathway and reverse β-oxidization pathway. The findings showed the importance of butyrate in CCE for caproate production.

Hydrogen-independent CO2 reduction dominates methanogenesis in five temperate lakes that differ in trophic states.

Emissions of microbially produced methane (CH4) from lake sediments are a major source of this potent greenhouse gas to the atmosphere. The rates of CH4 production and emission are believed to be influenced by electron acceptor distributions and organic carbon contents, which in turn are affected by anthropogenic inputs of nutrients leading to eutrophication. Here, we investigate how eutrophication influences the abundance and community structure of CH4 producing Archaea and methanogenesis pathways across time-resolved sedimentary records of five Swiss lakes with well-characterized trophic histories. Despite higher CH4 concentrations which suggest higher methanogenic activity in sediments of eutrophic lakes, abundances of methanogens were highest in oligotrophic lake sediments. Moreover, while the methanogenic community composition differed significantly at the lowest taxonomic levels (OTU), depending on whether sediment layers had been deposited under oligotrophic or eutrophic conditions, it showed no clear trend in relation to in situ distributions of electron acceptors. Remarkably, even though methanogenesis from CO2-reduction was the dominant pathway in all sediments based on carbon isotope fractionation values, taxonomic identities, and genomes of resident methanogens, CO2-reduction with hydrogen (H2) was thermodynamically unfavorable based on measured reactant and product concentrations. Instead, strong correlations between genomic abundances of CO2-reducing methanogens and anaerobic bacteria with potential for extracellular electron transfer suggest that methanogenic CO2-reduction in lake sediments is largely powered by direct electron transfer from syntrophic bacteria without involvement of H2 as an electron shuttle.

Single-Charge Tunneling in Codoped Silicon Nanodevices.

Silicon (Si) nano-electronics is advancing towards the end of the Moore's Law, as gate lengths of just a few nanometers have been already reported in state-of-the-art transistors. In the nanostructures that act as channels in transistors or depletion layers in pn diodes, the role of dopants becomes critical, since the transport properties depend on a small number of dopants and/or on their random distribution. Here, we present the possibility of single-charge tunneling in codoped Si nanodevices formed in silicon-on-insulator films, in which both phosphorus (P) donors and boron (B) acceptors are introduced intentionally. For highly doped pn diodes, we report band-to-band tunneling (BTBT) via energy states in the depletion layer. These energy states can be ascribed to quantum dots (QDs) formed by the random distribution of donors and acceptors in such a depletion layer. For nanoscale silicon-on-insulator field-effect transistors (SOI-FETs) doped heavily with P-donors and also counter-doped with B-acceptors, we report current peaks and Coulomb diamonds. These features are ascribed to single-electron tunneling (SET) via QDs in the codoped nanoscale channels. These reports provide new insights for utilizing codoped silicon nanostructures for fundamental applications, in which the interplay between donors and acceptors can enhance the functionalities of the devices.

Effective parameters for biogeochemical reaction rates in heterogeneous porous media

Biogeochemical reactions are the key processes that control the cycle and transformation of subsurface materials. However, biogeochemical reaction rates vary with observation scales. Such scaling effect are usually addressed with effective parameters, but it remains unclear how to estimate these effective parameters. In this work, we summarized those main factors that may affect the estimation of effective parameters, and discussed the variation of effective parameters under different combinations of factors in numerical simulations. The results indicate that the substrate sources strongly affect the estimation of the effective parameters. In scenarios with identical substrate sources, the effective parameters differ little from the intrinsic parameters, and thus the macroscopic effective biogeochemical reaction rate can be directly estimated from the volume-averaged concentrations of reactants. However, in scenarios with different substrate sources, the mean-field rates usually overestimate the macroscopic effective rates, and the extent of such overestimation diminishes with increasing flow velocity (or with decreasing Da). The above results provide meaningful insights into the estimation of macroscopic effective biogeochemical reaction rates in a variety of natural or artificial scenarios. We also decomposed the effective parameters to explain the above results. It is suggested that the homogeneous distribution of electron donors, electron acceptors and microorganisms, as well as their positive spatial correlation with each other, are the main reasons for the diminished scaling effect of biogeochemical reactions.

Design and performance analysis of GaN vertical JFETs with ion-implanted gates

We present a comprehensive performance analysis of vertical GaN JFETs via TCAD simulation with unique considerations for gates formed by Mg ion implantation into GaN. The dependence of the specific ON-resistance and pinch-off voltage on the gate and channel design parameters is first evaluated for a JFET with abrupt gate-channel junctions. Then, the influence of the gate acceptor concentration and distribution is studied to elucidate the consequences of incomplete acceptor activation or acceptor diffusion resulting from specialized post-implantation annealing techniques necessary for the activation of p-GaN. Examples of normally-ON and normally-OFF designs with 1.7 kV breakdown voltage for 1.2 kV applications are chosen for the activation and diffusion studies to demonstrate how the pinch-off and conduction characteristics are affected for different channel widths and doping concentrations conducive to each type of operation. Record low specific ON-resistance below 1 mΩ cm2 is predicted for both, but gate acceptor diffusion increases the channel resistance, especially for JFETs designed to be normally-OFF.

Modelling the electric field in non-fullerene organic solar cells: The effect of 1-chloronaphthalene additive

In this work, a perylene derivative was used as electron acceptor in organic solar cells and the morphology was optimized by using the 1-chlronaphthalene (CN) as additive. The power dissipation was simulated along the structure of OPV devices taking into count the interference occurring in stacked thin films under normal incidence by using the transfer matrix method (TMM). The TMM model has been used to simulate the electric field in organic solar cells having fullerene derivatives as electron acceptor. In opposite to the fullerenes, the perylene derivative also contributes to the photocurrent and, its optical and electrical features changed upon CN additive. Therefore, the monitoring through ellipsometry and TMM modelling contribute to understand the behaviour of the electromagnetic wave inside the device, providing insights about proper optimizations that can be performed in order to increase the G(x) rate and the Jsc parameter. This model takes into count the experimental values of refractive index n and extinction coefficient k acquired from the D:A film to simulate the spatial distribution of the electric field and provide valuable information about photovoltaic parameters. The results pointed out that chemical or physical modifications are required to improve the PDIC5 acceptor distribution along the bulk, as well as changes on the crystallinity, which can be achieved with the use of CN as additive.

High-Performance Layer-by-Layer organic solar cells enabled by Non-Halogenated solvent with 17.89% efficiency

Sequential layer-by-layer (LbL) deposition method, where ideal vertical morphology can be obtained, is a promising method for the fabrication of highly efficient organic solar cells (OSCs). But most LbL devices are prepared through toxic halogen solvents, hindering OSCs future commercial production. In this work, we have achieved bilayer devices based on PM6/BO-4Cl system for the first time with the non-halogenated solvent (o-xylene). Compared to BHJ devices, the efficiency of LbL devices was enhanced from 16.45 % to 17.03 %. On this basis, L8-BO was chosen as the third component doping into the acceptor layer and the performance of PM6/BO-4Cl: L8-BO ternary devices was further improved, realizing an outstanding PCE of 17.89 %, the highest value so far for halogen-free solvent processed LbL devices. The addition of L8-BO increased photon utilization and formed an alloy with BO-4Cl, while better regulating the donor–acceptor distribution in LbL structure, facilitating exciton dissociation and charge transport. More importantly, the PM6/BO-4Cl: L8-BO-based LbL devices retained 89 % of its original efficiency after 2000 h of placement. Our results demonstrate that tuning the material distribution precisely by LbL method, combined with the use of eco-friendly solvents is an effective way to achieve high performance ternary OSCs that benefiting the development of green energy technologies.

Entangled structure morphology by polymer guest enabling mechanically robust organic solar cells with efficiencies of over 16.5%

<h2>Summary</h2> Intrinsically stretchable organic solar cells (IS-OSCs) have attracted great attention as a promising power source for wearable electronics. However, reconciling high power conversion efficiency (PCE), reasonable stretchability, and thermal stability is a grand challenge. Herein, we have successfully improved the ductility and morphological stability of the PM6:BTP-eC9 blend film through introducing polymer PY-IT to form entangled structure morphology. Compared with the binary blend, the ternary system exhibits suppressed diffusion and crystallization of BTP-eC9 acceptor and load distribution across the entangled chain networks to dissipate the local energy. As a result, high efficiencies of 16.52% were obtained for the flexible OSCs based on polyethylene terephthalate (PET) substrate. Impressively, the PCE of IS-OSCs based on the elastomer substrate also achieved 15.3%. In this work, the study about intrinsic stretchability and morphological robustness demonstrates that high-performance IS-OSCs constitute a major step toward practical utilization in malleable electronic textiles.

Construction of sublimable pure organic ionic material with high solid luminescence efficiency based on anion-π+ interactions tuning strategy

Charged species with π-conjugated moieties play a vital role in the development of organic electronic field, but the executable strategy of attaining high luminescent efficiency with sublimable pure organic salts is rare due to their inherent ionic nature and low vapor pressure, extremely restricting their application in the field of organic optoelectronics via common vacuum evaporation method. In this work, a series of central-type organic salts based polycyclic aromatic hydrocarbon (PAH) core are developed because of their potential higher luminescence efficiency than that of reported terminal-type organic salts like protonated pyridine framework, and they are equipped with aggregation-induced emission enhancement performance and tunable emission. The analyses of spectral data, crystal packing, and theoretical simulation demonstrate that rationally dispersing surface charge of large π cation by regulating donor–acceptor (D-A) distribution facilitates to increase anion-π+ interactions and suppress the free rotation of phenyl groups, contributing to the fluorescence enhancement in the solid state. Notably, after tuning counter-ions’ steric hindrance and dispersed charges (BArF24−), the sublimable pure organic ionic materials are obtained with high solid luminescence efficiency, and its vacuum-evaporated organic light-emitting diode (OLED) is prepared based on pure organic salt with bright yellow emission. Such inspiring results offer us new alternative material system for the organic optoelectronics.

Toward High‐Performance Semitransparent Organic Photovoltaics with Narrow‐Bandgap Donors and Non‐Fullerene Acceptors

AbstractSolar energy offers an alternative solution to the global community's growing energy demands. Semitransparent organic photovoltaics (ST‐OPVs) have received tremendous attention due to their tunable energy levels and rising power conversion efficiency (PCE). Because of its transparency, ST‐OPVs are able to serve as the power‐generating roof of the greenhouse, and color‐tunable walls/windows for modern buildings or façades. With the rapid development of narrow‐bandgap semiconductors to absorb near‐infrared photons, the performances of ST‐OPVs has progressed with PCEs over 12% with average visible transmittances over 20%. Here, recent developments in ST‐OPVs based on narrow‐bandgap donors and non‐fullerene acceptors are reviewed. Several strategies for chemical structures design have been reported to lower bandgaps semiconductor materials. The recent developments of non‐fullerene acceptor structures for ST‐OPVs are categorized into A‐D‐A, A‐π‐D‐π‐A, and A‐DAD‐A by the structure alignment. From device perspectives, the strategies such as ternary blend, distributions of donors and acceptors in active layers, tandem and transparent conductive electrodes for high‐performance ST‐OPVs are summarized. To conclude, some insightful guidelines for future developments in ST‐OPVs from both materials and device points of views are provided.

3D Nanoscale Morphology Characterization of Ternary Organic Solar Cells

It is highly desired to develop advanced characterization techniques to explore the 3D nanoscale morphology of the complicated blend film of ternary organic solar cells (OSCs). Here, ternary OSCs are constructed by incorporating the nonfullerene acceptor perylenediimide (PDI)-diketopyrrolopyrrole (DPP)-PDI and their morphology is characterized in depth to understand the performance variation. In particular, photoinduced force microscopy (PiFM) coupled with infrared laser spectroscopy is conducted to qualitatively study the distribution of donor and acceptors in the blend film by chemical identification and to quantitatively probe the segmentation of domains and the domain size distribution after PDI-DPP-PDI acceptor incorporation by PiFM imaging and data processing. In addition, the energy-filtered transmission electron microscopy with energy loss spectra is utilized to visualize the nanoscale morphology of ultrathin cross-sections in the configuration of the real ternary device for the first time in the field of photovoltaics. These measurements allow to "view" the surface and cross-sectional morphology and provide strong evidence that the PDI-DPP-PDI acceptor can suppress the aggregation of the fullerene molecules and generate the homogenous morphology with a higher-level of the molecularly mixed phase, which can prevent the charge recombination and stabilize the morphology of photoactive layer.

Theory and Analysis of Single-Molecule FRET Experiments.

Inter-dye distances and conformational dynamics can be studied using single-molecule FRET measurements. We consider two approaches to analyze sequences of photons with recorded photon colors and arrival times. The first approach is based on FRET efficiency histograms obtained from binned photon sequences. The experimental histograms are compared with the theoretical histograms obtained using the joint distribution of acceptor and donor photons or the Gaussian approximation. In the second approach, a photon sequence is analyzed without binning. The parameters of a model describing conformational dynamics are found by maximizing the appropriate likelihood function. The first approach is simpler, while the second one is more accurate, especially when the population of species is small and transition rates are fast. The likelihood-based analysis as well as the recoloring method has the advantage that diffusion of molecules through the laser focus can be rigorously handled.

Förster resonance energy transfer in finite length systems and porous media

Förster Resonance Energy Transfer (FRET) is a mechanism widely used to describe the luminescent behavior of a great variety of systems. However, there is a strong need for a complete model of Förster theory to understand donor-acceptor interactions in different confinement geometries and their effects on the luminescent dynamics. Here, a methodology based on Förster theory that allows finding the probability distribution of donors and acceptors in systems of any geometry is presented. We have considered the particular cases of lines with finite length, finite cylinders, and bi-dimensional arrangements of lines and cylinders. Furthermore, using our results, we calculate the quantum yield as a function of the geometric parameters of the structures. Our numerical results show that this methodology is useful to calculate and predict the donor luminescent dynamics in structures of finite length. We find that our model explains the decrease of the transferred energy from donors to acceptors with the separation between lines or cylinders, this behavior is physically consistent. The model presented here extends the use of FRET to the study of structures with bi-dimensional arrays of lines or cylinders (as could be the case of porous media), and finite cylinder structures (as could be the case of nanotubes). In our knowledge, this work is the first theoretical approach to describe the donor-acceptor luminescent dynamics in this kind of systems.