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Concentration effects on the thermally-activated transport of polarons in conducting polymers
摘要： The impact of the polaron concentration on the temperature-mediated charge transport in one-dimensional organic materials is studied. Within the scope of a tight-binding description, our findings reveal that high-temperature diffusivity tends to increase as polaron concentration increases. Moreover, the activation energy for the polaron transport also increases with polaron concentration. Importantly, the polaron diffusivity follows an Arrhenius-like behavior with low activation energy.
关键词： Activation energy,Organic materials,Polaron concentration,Diffusivity
更新于2025-09-23 15:23:52
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Investigations on the quantum chemical studies and physico-chemical properties of an opto-electronic material 1-Allyl-2-Aminopyridine-1-ium bromide
摘要： In the present work, the dual approach of quantum chemical studies and experimental characterizations of the title compound 1-Allyl-2-Aminopyridine-1-ium bromide (1A2APB) were carried out for the first time. The molecular geometry of 1A2APB was optimized by density functional theory (DFT) using B3LYP/6-311++G (d,p) basis set. The optimized geometric structural parameters were compared with the experimental findings and discussed. The dipole moment (μ) and first hyperpolarizability (β) were calculated to predict the NLO behavior. The frontier molecular orbital (FMO), molecular electrostatic potential (MESP), Mulliken atomic charge and thermodynamic properties were investigated to get a better insight of the molecular properties. Stability of the compound arising from hyper-conjugative interactions, intra-molecule re-hybridization and charge delocalization within the molecule were analyzed using NBO analysis. Further, 1A2APB was synthesized and good quality single crystals were grown by slow evaporation technique. Studies such as microanalysis and powder XRD were performed to ascertain material composition and phase respectively. The various characteristic functional groups were identified through FT-IR spectroscopic analyses. The NLO efficiency was measured to be about greater than 5 times that of standard KDP. Thermal behaviors were explored by the simultaneous TG/DTA-DSC thermograms. The UV–Vis–NIR spectral data and fluorescence spectrum were recorded to explore the optical transmission and emission properties respectively. The dielectric properties were evaluated as a function of frequency at various temperatures. The photoconducting nature was analyzed through photoconductivity measurement. The Vicker’s microhardness test was performed at room temperature from which the mechanical stability was analyzed through the classical Meyer’s relation.
关键词： Photoconductivity,Powder XRD analysis,DFT calculations,Organic materials,Non-linear optics,Crystal growth
更新于2025-09-23 15:23:52
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Asymmetric Pentacenes for Solution-Processed Organic Field-Effect Transistors
摘要： Background: Symmetrically substituted pentacenes have been traditionally used as semiconductors for solution-processed p-channel Organic Field Effect Transistors (OFETs). The aims of this paper are to introduce asymmetrically substituted pentacenes in the active layer and to examine the impact of the polyaromaticity of the pendant groups on the device characteristics. Methods: Research and online content related to asymmetrically substituted pentacenes is reviewed, the synthesis of the different pentacenes is described and the procedure used to introduce these semiconductors in devices is detailed. Comparison with a reference material is provided. Results: Extension of the polyaromaticity of the pendant group of pentacene greatly contributes to enhance the device performances. Impact of the pendant group on the morphology of the active layer is evidenced by the roughness decreasing with the increase of aromatic ring in the substituent. Conclusion: We demonstrate the extension of the π-conjugation of the aromatic end-group to drastically impact both ON/OFF ratio and charge carrier mobilities, mainly due to various degree of crystal formation characteristics in the film. Best results were obtained with the most extended one, namely the anthracene moiety which showed a mobility comparable to that of the benchmark TIPS-pentacene with OFETs that used hexamethyldisilazane as the gate dielectric passivation layer.
关键词： solution-process,semiconductor,organic materials,OFET,Mobility,TIPS-pentacene
更新于2025-09-23 15:23:52
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Azaindolo[3,2,1-jk]carbazoles: New Building Blocks for Functional Organic Materials
摘要： The preparation and characterization of twelve azaindolo[3,2,1-jk]carbazoles is being presented. Ring closing C-H activation allowed for the convenient preparation of six mono and six twofold nitrogen substituted indolo[3,2,1-jk]carbazole derivatives whereupon ten of the materials have not been described in literature before. The photophysical and electrochemical characterization of the developed materials revealed a significant impact of the incorporation of pyridine like nitrogen into the fully planar indolo[3,2,1-jk]carbazole backbone. Furthermore, the nitrogen position decisively impacts intermolecular hydrogen bonding and thus the solid state alignment. Ultimately, the versatility of the azaindolo[3,2,1-jk]carbazoles scaffold suggests this class of materials as an attractive new building block for the design of functional organic materials.
关键词： heterocycles,functional organic materials,C-H activation
更新于2025-09-23 15:22:29
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Recent Advances in Isoindigo-Inspired Organic Semiconductors
摘要： Over the past decade, isoindigo has become a widely used electron-deficient subunit in donor-acceptor organic semiconductors, and these isoindigo-based materials have been widely used in both organic photovoltaic (OPV) devices and organic field effect transistors (OFETs). Shortly after the development of isoindigo-based semiconductors, researchers began to modify the isoindigo structure in order to change the optoelectronic properties of the resulting materials. This led to the development of many new isoindigo-inspired compounds; since 2012, the Kelly Research Group has synthesized a number of these isoindigo analogues and produced a variety of new donor-acceptor semiconductors. In this Personal Account, recent progress in the field is reviewed. We describe how the field has evolved from relatively simple donor-acceptor small molecules to structurally complex, highly planarized polymer systems. The relevance of these materials in OPV and OFET applications is highlighted, with particular emphasis on structure-property relationships.
关键词： isoindigo,organic field effect transistors,organic materials,organic photovoltaics,conjugated polymers
更新于2025-09-23 15:21:01
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In-Line Holography in Transmission Electron Microscopy for the Atomic Resolution Imaging of Single Particle of Radiation-Sensitive Matter
摘要： In this paper, for the first time it is shown how in-line holography in Transmission Electron Microscopy (TEM) enables the study of radiation-sensitive nanoparticles of organic and inorganic materials providing high-contrast holograms of single nanoparticles, while illuminating specimens with a density of current as low as 1–2 e???2s?1. This provides a powerful method for true single-particle atomic resolution imaging and opens up new perspectives for the study of soft matter in biology and materials science. The approach is not limited to a particular class of TEM specimens, such as homogenous samples or samples specially designed for a particular TEM experiment, but has better application in the study of those specimens with differences in shape, chemical composition, crystallography, and orientation, which cannot be currently addressed at atomic resolution.
关键词： TEM,radiation damage,atomic resolution imaging,nanostructured drugs,organic materials,in-line holography,soft matter,single particle imaging
更新于2025-09-23 15:19:57
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Electronic and optoelectronic performance of nano-Vanadyl 2,3-naphthalocyanine/n-Si (organic/inorganic) solar cells: Temperature dependence
摘要： Vanadyl 2,3-naphthalocyanine (VONc) /n-Si heterojunction was prepared by vacuum deposition of VONc compound onto n-Si single crystals. The analysis of the X-ray diffraction pattern and the scanning electron microscopy images reveal the nanostructure nature of the deposited VONc film. At low voltage, the temperature dependence of current density-voltage characteristics corroborates that the multi-tunneling mechanism is the dominant current mechanism for the dark forward bias. In the case of the higher forward bias (0.4<V<2 V), the conduction mechanism is a space charge limited current dominated by a single trap level. The capacitance-voltage characteristics imply that the junction has an abrupt heterojunction description and the value of built-in voltages, at room temperature, was estimated to be 0.67 eV. The values of the open-circuit voltage, the short-circuit current, fill factor and power conversion efficiency under illumination (100 mW/cm2) and at room temperatures were calculated to be 0.70 V, 11.30 mA/cm2, 0.394 and 3.12 %, respectively. These results indicate that VONc/n-Si heterojunction is characterized by remarkable considerable photovoltaic properties comparing with the other organic/inorganic heterojunctions.
关键词： photovoltaic,nanostructure films,Heterojunctions,organic materials
更新于2025-09-19 17:13:59
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Charge Transport and Photovoltaic Properties of Conjugated Polymer PTB7:PC71BM Based Solar Cells
摘要： We investigate the charge transport in organic solar cells based on PTB7:PC71BM by measuring the J (V) characteristics at different temperatures (140–325 K). In dark, two models dominate the transport. The Ohmic law overcomes for the low applied low voltages, and for high voltages the trapped charge limited current governs the transport with an average total concentration of trap around 5.62 × 1015 cm?3. At higher voltages there is evidence of an electrode-to-bulk limited transition, with conductivity dominated by the Poole–Frenkel effect. The photovoltaic conversion properties of the junction were also studied by carrying out the J–V measurements at room temperature under illumination of 100 mW/cm2 and a power conversion efficiency of 6.49% has been achieved. the other cell parameters, the short-circuit current density JSC, the open circuit voltage VOC and de fill factor FF, were found to be 12.87 mA/cm2, 0.77 V and 0.65 respectively. These values were compared with other organic solar cells found in literature.
关键词： Charge transport,Photovoltaics,Organic materials,Trap density
更新于2025-09-19 17:13:59
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Two different types of S-shaped J-V characteristics in organic solar cells
摘要： In this paper, S-shaped characteristics of organic solar cells (OSCs) are analyzed by a drift–diffusion model which includes charge carrier surface recombination and thermal injection on the anode and cathode through boundary conditions. By varying surface recombination velocities (SRVs) for electrons and holes on both contacts and the injection barrier heights for majority carriers, two different S-shaped deviations in OSCs J-V characteristics were observed. The first type of S-shaped J-V characteristic manifests the S-shape bending in the vicinity of the voltage axis, after which it rises almost exponentially. This kind of S-shape deformation was found to arise from the finite SRVs. The second type of the S-shaped J-V characteristic also makes a kink near the voltage axis but proceeds to grow monotonically, having only one saddle point. The S-shaped J-V curve of this kind turned out to be the consequence of the electron injection barrier height larger than 0.2 eV. The validity of our model is confirmed by comparing the simulated J-V curves with the experimentally obtained data. The model has been applied to the ITO/PEDOT:PSS/P3HT:PCBM/Al and ITO/PEDOT:PSS/P3HT:ICBA/Al solar cells. For the P3HT:PCBM based solar cells, the regular J-shaped J-V curves were measured, while for the P3HT:ICBA solar cells, the J-V curves with anomalous S-shape behavior were recorded. All experimentally obtained J-V curves were reproduced very well with our model. It seems that the ITO/PEDOT:PSS/ P3HT:ICBA/Al solar cell S-shaped J-V curve originates from the electron barrier height on the cathode contact, rather than from the low surface recombination on the electrodes.
关键词： Solar cells,Drift–diffusion model,Organic materials,S-shaped J-V curve
更新于2025-09-19 17:13:59
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Device characteristics and material developments of indoor photovoltaic devices
摘要： Indoor photovoltaics (IPVs), which convert the indoor light energy into direct electricity, have attracted research attention due to their potential use as an excellent amicable solution of sustainable power source to drive low-power-needed sensors for the internet of things (IoT) applications. Our daily life adopts various indoor light sources, such as indirect sunlight, incandescent lamps, halogen lamps, ?uorescent lamps, and LED bulbs, that typically deliver lower light intensity (200–1000 lux) as compared to that of sun light (～100,000 lx). In this review, we ?rstly classi?ed the indoor lights depending on their working mechanism and resulting emission spectrum. Because the indoor light intensities are rather low that may lead to overestimate/underestimate the power conversion e?ciency (PCE) of IPV devices, then, the cautious points for correctly measuring the indoor light intensity as well as the device characteristics are summarized. Several light sources with various light intensities are reported so far, but for lack of common or standard calibration meter that induces a ambiguity in PCE determination, so we suggest/propose to use a universal LED lux meter with NIST-traceable calibration (e.g. Extech LT40-NIST) and also recommended the device results are expressed in maximum power point Pmax along with PCE values. It is generally believed that the materials play key roles on the performance of the IPV devices. Since the indoor light intensity is much weaker as compared to that of outdoor irradiation, the typical inferior photo-stability of organic materials under sunlight may not be as crucial as we considered to harvest indoor light energy, opening a great room for organic IPV material developments. In principle, all materials for outdoor PVs may also be useful for IPVs, but the fundamental material requirement for IPVs which needs su?ciently covering the absorption range between the 350–700 nm with high molar extinction coe?cient should be primarily concerned. In order to get the thorough knowledge of materials for achieving better e?cient IPVs, the reported IPVs were collected and summarized. According to these reports, the materials utilized for IPVs have been classi?ed into two major groups, inorganic and organic materials, then divided them into several sub-classes, including (1) silicon and III-V semiconductor photovoltaics, (2) dye-sensitized photovoltaics, (3) organic photovoltaics, and (4) perovskite-based photovoltaics, depend on their structural nature and device working principle. For every individual class, the structure-property-e?ciency relationship of the materials was analyzed together with the highlights on the best e?ciency material, challenge and perspective. For inorganic IPV materials, III-V semiconductor GaAs-based IPVs performed a very impressive PCE (28%). For dye sensitizers, there are more ?exible strategies to modulate the absorption pro?les of organic materials. A high e?ciency dye-sensitized solar cell (DSSC)-based IPV with a PCE up to 32% has been successfully realized with co-sensitized dyes. For organic solar cell (OSC)-based IPVs, fullerene-based acceptors are advantageous for their well-matching desired absorption range and superior electron transport features. A recent OSC-based IPV with the active layer composed of dithienobenzene-based donor and fullerene acceptor was reported to deliver a PCE of 28%. Among these emerging photovoltaic materials, it is no doubt that perovskites (e.g. CH3NH3PbI3) are superior for solar energy conversion due to the crystallinity for good charge transport, better spectral coverage and the low exciton binding energy. Until very recent, a perovskite-based IPV with a PCE of 35% was reported with good stability by the incorporation of an ionic liquid for e?ectively passivating the surface of the perovskite ?lm, indicating the bright prospect of perovskite for IPV application. Overall, the review on these reports implies the essential criteria of materials suitable for IPVs that may trigger new ideas for developing future champion materials for various devices and the realization of practical IPV applications.
关键词： Organic solar cells,Dye-sensitized solar cells,Silicon and III-V semiconductors,Perovskite materials,Power conversion efficiency,Internet of Things,Organic materials,Indoor photovoltaics
更新于2025-09-16 10:30:52