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Formation of Occupied and Unoccupied Hybrid Bands at Interfaces between Metals and Organic Donors/Acceptors
摘要： Efficient charge transport in organic semiconductors and at their interfaces with electrodes is crucial for the performance of organic molecule-based electronic devices. Band formation fosters effective transport properties and can be found in organic single crystals of large π-stacking aromatic molecules. However, at molecule/metal interfaces hybrid band formation and band dispersion is a rarely observed phenomenon. Using angle-resolved two-photon photoemission supported by density functional theory calculations we demonstrate such band formation for two different molecule/metal systems, namely tetrathiafulvalene (TTF)/Au(111) and tetrafluoro-tetracyanoquinodimethane (F4TCNQ)/Au(111), in the energy region of occupied as well as unoccupied electronic states. In both cases strong adsorbate/substrate interactions result in formation of interface states due to hybridization between localized molecular states and delocalized metal bands. These interface states exhibit significant dispersions. Our study reveals that hybridization in combination with an extended well-ordered adsorption structure of the π-conjugated organic molecules is a striking concept to receive and experimentally observe band formation at molecule/metal interfaces.
关键词： band formation,organic semiconductors,molecule/metal interfaces,hybridization,charge transport,density functional theory,angle-resolved two-photon photoemission
更新于2025-09-23 15:21:21
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Growth mechanisms of F4-TCNQ on inorganic substrates and nanostructures
摘要： The organic semiconductor tetrafluorotetracyanoquinodimethane (F4-TCNQ) is a promising candidate for the doping of organic semiconductors, two-dimensional materials and inorganic compounds, such as ZnO, and also to enhance the charge carrier injection at contacts in organic electronics. In order to evaluate its applicability as a functionalization material or as an electrically active part in devices, we present a systematic study on the growth mode of F4-TCNQ beyond the first few monolayers on different inorganic substrates that cover a broad variety regarding their physical, chemical and morphological surface properties. The materials used are silicon, silicon carbide, graphene on silicon, sapphire, nanocrystalline diamond, as well as gallium nitride (GaN) layers and nanowire arrays. While the surface termination influences the shape and morphology of the islands of F4-TCNQ which form on all substrates investigated, no significant dependence of the growth mode on the substrate doping type and concentration is observed. GaN nanowires are found to act as nucleation sites for F4-TCNQ islands and to be covered by few monolayers of F4-TCNQ forming a closed coaxial shell. In conclusion, F4-TCNQ is identified to nucleate via Stranski-Krastanov growth consisting of monolayers and islands of different size and shape. The findings in this work provide basic growth information for the implementation of F4-TCNQ as functionalization material for nanowire-based applications.
关键词： GaN nanowires,surface functionalization,growth mode,organic semiconductors,organic electronics,surface doping,F4-TCNQ
更新于2025-09-23 15:21:01
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Chemical and Biomolecule Sensing with Organic Field-Effect Transistors
摘要： The strong and controllable chemical sensitivity of organic semiconductors (OSCs) and the amplification capability of transistors in circuits make use of OSC-based field-effect transistors compelling for chemical sensors. Analytes detected and assayed range from few-atom gas-phase molecules that may have adverse health and security implications to biomacromolecules (proteins, nucleic acids) that may be markers for physiological processes and medical conditions. This review highlights recent progress in organic field-effect transistor (OFET) chemical sensors, emphasizing advances from the past 5 years and including aspects of OSC morphology and the role of adjacent dielectrics. Design elements of the OSCs and various formats for the devices are illustrated and evaluated. Challenges associated with the present state of the art and future opportunities are also discussed.
关键词： organic field-effect transistors,organic semiconductors,dielectrics,biomacromolecules,chemical sensors
更新于2025-09-23 15:21:01
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Lead-free perovskite/organic semiconductor vertical heterojunction for highly sensitive photodetectors
摘要： In recent years, photodetectors based on organic-inorganic lead halide perovskites have been studied extensively. However, the inclusion of lead in those materials can cause severe human health and environmental problems, which is undesirable for practical applications. Here, we report high-performance photodetectors with a tin-based perovskite/PEDOT:PSS vertical heterojunction. The device demonstrates broadband photo-response from NIR to UV. The maximum responsivity and gain are up to 2.6 × 106 A/W and 4.7 × 106, respectively. Moreover, a much shorter response time and higher detectivity can be achieved by reducing the thickness of PEDOT:PSS. The outstanding performance is due to the excellent optoelectronic properties of the perovskite and the photo-gating effect originated from the heterojunction. Furthermore, devices fabricated on flexible substrates can demonstrate not only high sensitivity but also excellent bending stability. This work opens up the opportunity of using lead-free perovskite in highly sensitive photodetectors with vertical heterojunctions.
关键词： Photo-gating,heterojunction,organic semiconductors,Photodetectors,Lead free perovskites
更新于2025-09-23 15:21:01
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Photovoltaic organic interface for neuronal stimulation in the near-infrared
摘要： Organic materials, such as conjugated polymers, are attractive building blocks for bioelectronic interfaces. In particular, organic semiconductors show excellent performance in light-mediated excitation and silencing of neuronal cells and tissues. However, the main challenges of these organic photovoltaic interfaces compared to inorganic prostheses are the limited adhesion of conjugated polymers in aqueous environments and the exploitation of materials responsive in the visible spectrum. Here, we show a photovoltaic organic interface optimized for neuronal stimulation in the near-infrared spectrum. We adjusted the organic materials by chemical modification in order to improve the adhesion in an aqueous environment and to modulate the photoelectrical stimulation efficiency. As proof-of-principle, we tested this interface on explanted degenerated mice retinas, thus providing results on the efficiency and reliability of the device as an implant for neural stimulation.
关键词： organic semiconductors,bioelectronic interfaces,neuronal stimulation,near-infrared spectrum,photovoltaic interfaces
更新于2025-09-23 15:21:01
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Polariton condensation in photonic crystals with high molecular orientation
摘要： We study Frenkel exciton-polariton Bose–Einstein condensation in a two-dimensional defect-free triangular photonic crystal with an organic semiconductor active medium containing bound excitons with dipole moments oriented perpendicular to the layers. We ?nd photonic Bloch modes of the structure and consider their strong coupling regime with the excitonic component. Using the Gross– Pitaevskii equation for exciton polaritons and the Boltzmann equation for the external exciton reservoir, we demonstrate the formation of condensate at the points in reciprocal space where photon group velocity equals zero. Further, we demonstrate condensation at non-zero momentum states for transverse magnetic-polarized photons in the case of a system with incoherent pumping, and show that the condensation threshold varies for different points in the reciprocal space, controlled by detuning.
关键词： organic semiconductors,photonic crystalls,photonics,exciton polaritons,Bose–Einstein condensate
更新于2025-09-23 15:21:01
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Efficiency of Charge-Transfer Doping in Organic Semiconductors Probed with Quantitative Microwave and Direct-Current Conductance
摘要： Although molecular charge-transfer doping is widely used to manipulate carrier density in organic semiconductors, only a small fraction of charge carriers typically escape the Coulomb potential of dopant counterions to contribute to electrical conductivity. Here, we utilize microwave and direct-current (DC) measurements of electrical conductivity to demonstrate that a high percentage of charge carriers in redox-doped semiconducting single-walled carbon nanotube (s-SWCNT) networks is delocalized as a free carrier density in the π-electron system (estimated as >46% at high doping densities). The microwave and four-point probe conductivities of hole-doped s-SWCNT films quantitatively match over almost 4 orders of magnitude in conductance, indicating that both measurements are dominated by the same population of delocalized carriers. We address the relevance of this surprising one-to-one correspondence by discussing the degree to which local environmental parameters (e.g., tube?tube junctions, the relative Coulombic stabilization, and local bonding environment) may impact magnitudes of each transport measurement.
关键词： microwave conductivity,organic semiconductors,single-walled carbon nanotube,charge-transfer doping,DC conductivity
更新于2025-09-23 15:21:01
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Chargea??Transfera??Controlled Growth of Organic Semiconductor Crystals on Graphene
摘要： Controlling the growth behavior of organic semiconductors (OSCs) is essential because it determines their optoelectronic properties. In order to accomplish this, graphene templates with electronic-state tunability are used to affect the growth of OSCs by controlling the van der Waals interaction between OSC ad-molecules and graphene. However, in many graphene-molecule systems, the charge transfer between an ad-molecule and a graphene template causes another important interaction. This charge-transfer-induced interaction is never considered in the growth scheme of OSCs. Here, the effects of charge transfer on the formation of graphene–OSC heterostructures are investigated, using fullerene (C60) as a model compound. By in situ electrical doping of a graphene template to suppress the charge transfer between C60 ad-molecules and graphene, the layer-by-layer growth of a C60 film on graphene can be achieved. Under this condition, the graphene–C60 interface is free of Fermi-level pinning; thus, barristors fabricated on the graphene–C60 interface show a nearly ideal Schottky–Mott limit with efficient modulation of the charge-injection barrier. Moreover, the optimized C60 film exhibits a high field-effect electron mobility of 2.5 cm2 V?1 s?1. These results provide an efficient route to engineering highly efficient optoelectronic graphene–OSC hybrid material applications.
关键词： growth template,organic semiconductors,organic electronics,graphene,charge transfer
更新于2025-09-23 15:19:57
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Water-Processed Organic Solar Cells with Open-Circuit Voltages Exceeding 1.3V
摘要： Conjugated polyelectrolytes are commonly employed as interlayers to modify organic solar cell (OSC) electrode work functions but their use as an electron donor in water-processed OSC active layers has barely been investigated. Here, we demonstrate that poly[3-(6’-N,N,N-trimethyl ammonium)-hexylthiophene] bromide (P3HTN) can be employed as an electron donor combined with a water-soluble fullerene (PEG-C60) into eco-friendly active layers deposited from aqueous solutions. Spin-coating a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) layer prior to the P3HTN:PEG-C60 active layer deposition considerably increases the open-circuit voltage (Voc) of the OSCs to values above 1.3 V. Along with this enhanced Voc, the OSCs fabricated with the PEDOT:PSS interlayers exhibit 10-fold and 5-fold increases in short-circuit current density (Jsc) with respect to those employing bare indium tin oxide (ITO) and molybdenum trioxide coated ITO anodes, respectively. These findings suggest that the enhanced Jsc and Voc in the water-processed OSCs using the PEDOT:PSS interlayer cannot be solely ascribed to a better hole collection but rather to ion exchanges taking place between PEDOT:PSS and P3HTN. We investigate the optoelectronic properties of the newly formed polyelectrolytes using absorption and photoelectron spectroscopy combined with hole transport measurements to elucidate the enhanced photovoltaic parameters obtained in the OSCs prepared with PEDOT:PSS and P3HTN.
关键词： frontier orbitals,organic semiconductors,organic solar cells,conjugated polyelectrolytes,sustainable fabrication
更新于2025-09-23 15:19:57
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Deep Learning for Optoelectronic Properties of Organic Semiconductors
摘要： Atomistic modeling of the optoelectronic properties of organic semiconductors (OSCs) requires a large number of excited-state electronic-structure calculations, a computationally daunting task for many OSC applications. In this work, we advocate the use of deep learning to address this challenge and demonstrate that state-of-the-art deep neural networks (DNNs) are capable of accurately predicting various electronic properties of an important class of OSCs, i.e., oligothiophenes (OTs), including their HOMO and LUMO energies, excited-state energies and associated transition dipole moments. Among the tested DNNs, SchNet shows the best performance for OTs of different sizes, achieving average prediction errors in the range of 20-80meV. We show that SchNet also consistently outperforms shallow feed-forward neural networks, especially in difficult cases with large molecules or limited training data. We further show that SchNet could predict the transition dipole moment accurately, a task previously known to be difficult for feed-forward neural networks, and we ascribe the relatively large errors in transition dipole prediction seen for some OT configurations to the charge-transfer character of their excited states. Finally, we demonstrate the effectiveness of SchNet by modeling the UV-Vis absorption spectra of OTs in dichloromethane and a good agreement is observed between the calculated and experimental spectra.
关键词： optoelectronic properties,organic semiconductors,transition dipole moment,SchNet,oligothiophenes,deep learning,UV-Vis absorption spectra
更新于2025-09-23 15:19:57