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Improved Transistor Performance by Modulating Molecular Packing with Donor and Acceptor Moieties
摘要： The joint of the donor and acceptor moieties allows a facile and effective strategy to develop novel organic conjugated materials. However, few works report the understanding of the donor-acceptor interactions at the molecular level. Herein, we develop three small molecules contain one acceptor motif with different amounts of the donor unit. By the combination of theoretical calculation and energy level characterization, the lowest occupied molecular orbital (LUMO) levels of the three molecules were proven to be almost identical. The molecular packing modes were evaluated from crystal structure prediction. Due to the donor-acceptor interactions, the packing mode can be tuned from the 1D slipped stacking to the 2D brick layer. The 2D molecular packing and charge transport channel endowed the materials a higher electron mobility of 3.29 cm2 V?1 s?1 in the single-crystal field-effect transistors after such modulation.
关键词： organic field-effect transistor,conjugated molecules,donor-acceptor,crystal structure prediction
更新于2025-09-23 15:22:29
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4H-pyranylidene-based small push-pull chromophores: Synthesis, structure, electronic properties and photovoltaic evaluation
摘要： The synthesis and electrochemical and optical characterizations of four new 4H-pyranylidene-based push-pull molecules are reported herein as well as their evaluation as donor materials for organic photovoltaics. Studied systems exhibit good absorption properties and appropriate LUMO levels for a photoinduced electron transfer to C60. Bilayer organic solar cells fabricated from these new donors and C60 as the acceptor gave photocurrent however with low power conversion efficiencies. As shown by X-ray diffraction and theoretical calculations, titled molecules present a twisted structure which may prevent the formation of suitable π-π contacts between adjacent molecules hence explaining their low photovoltaic performance.
关键词： Push-pull systems,Small conjugated molecules,4H-pyranylidene,Organic photovoltaics
更新于2025-09-23 15:21:01
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Surface-Controlled Crystal Alignment of Naphthyl End-Capped Oligothiophene on Graphene: Thin-Film Growth Studied by <i>In Situ</i> X-ray Diffraction
摘要： We report on the microstructure, morphology, and growth of 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2) thin films deposited on graphene, characterized by grazing-incidence X-ray diffraction (GIXRD) and complemented by atomic force microscopy (AFM) measurements. NaT2 is deposited on two types of graphene surfaces: custom-made samples where CVD-grown graphene layers are transferred onto a Si/SiO2 substrate by us and common commercially transferred CVD graphene on Si/SiO2. Pristine Si/SiO2 substrates are used as a reference. The NaT2 crystal structure and orientation depend strongly on the underlying surface, with the molecules predominantly lying-down on the graphene surface (face-on orientation) and standing nearly out-of-plane (edge-on orientation) on the Si/SiO2 reference surface. Post growth GIXRD and AFM measurements reveal that the crystalline structure and grain morphology differ depending on whether there is polymer residue left on the graphene surface. In situ GIXRD measurements show that the thickness dependence of the intensity of the (111) reflection from the crystalline edge-on phase does not intersect zero at the beginning of the deposition process, suggesting that an initial wetting layer, corresponding to 1-2 molecular layers, is formed at the surface-film interface. By contrast, the (111) reflection intensity from the crystalline face-on phase grows at a constant rate as a function of film thickness during the entire deposition.
关键词： surface-controlled alignment,molecular orientation,conjugated oligomers,GIXRD,small π-conjugated molecules,two-dimensional materials
更新于2025-09-19 17:13:59
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“Twisted” conjugated molecules as donor materials for efficient all-small-molecule organic solar cells processed with tetrahydrofuran
摘要： High-performance organic semiconductors that can be processed with environmentally benign solvents are highly desirable for printable optoelectronics. Herein, four acceptor–donor–acceptor conjugated molecules, i.e., DRTT-T, DRTT-R, DRTT-OR and DRTT, with 3-ethylrhodanine as acceptor terminal units and 2,5-bis(4,8-di(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b0]dithiophen-2-yl)thieno[3,2-b]thiophene derivatives as donor units were synthesized. 5-(2-Ethylhexyl)thiophen-2-yl, 2-ethylhexyl and 2-ethylhexyloxy were introduced at the b-positions of the central thieno[3,2-b]thiophene (TT) units in DRTT-T, DRTT-R and DRTT-OR, respectively, and unsubstituted TT was used as the central unit in DRTT. As revealed by density functional theory calculations, DRTT-OR and DRTT adopt an almost planar geometry, while DRTT-T and DRTT-R have “twisted” backbones due to the introduction of bulky substituents on TT units. Di?ering from DRTT-OR and DRTT which are only well soluble in chlorinated solvents such as chloroform, DRTT-T and DRTT-R also show high solubility in “greener” solvents, including toluene and tetrahydrofuran (THF). Non-fullerene small molecule (NFSM) organic solar cells (OSCs) were fabricated with these molecules as donor materials. The molecules (DRTT-T and DRTT-R) with twisted backbones displayed remarkably higher device performance compared to more planar ones (DRTT-OR and DRTT), attributed to the formation of ordered face-on microstructures with p–p stacking distances of 3.7–3.8 ?A and interpenetration networks of donor and acceptor components in the blend ?lms based on DRTT-T and DRTT-R. Most importantly, the power conversion e?ciencies (PCEs) of DRTT-T and DRTT-R based devices processed with THF reached 9.37% and 10.45%, respectively. This study demonstrates that “twisting” conjugated backbones is an appropriate strategy to design eco-friendly solvent processable organic semiconductors for high-e?ciency OSCs.
关键词： conjugated molecules,tetrahydrofuran,organic solar cells,donor materials,power conversion efficiencies
更新于2025-09-16 10:30:52
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Tailoring a Molecule’s Optical Absorbance Using Surface Plasmonics
摘要： Understanding the interaction of light with molecules physisorbed on substrates is a fundamental problem in photonics, with applications in biosensing, photovoltaics, photocatalysis, plasmonics, and nanotechnology. However, the design of novel functional materials in silico is severely hampered by the lack of robust and computationally efficient methods for describing both molecular absorbance and screening on substrates. Here we employ our hybrid G0[W0 + ?W]-BSE implementation, which incorporates the substrate via its screening ?W at both the quasiparticle G0W0 level and when solving the Bethe-Salpeter equation (BSE). We show this method can be used to both efficiently and accurately describe the absorption spectra of physisorbed molecules on metal substrates and thereby tailor the molecule’s absorbance by altering the surface plasmon’s energy. Specifically, we investigate how the optical absorption spectra of three prototypical π-conjugated molecules: benzene (C6H6), terrylene (C30H16) and fullerene (C60), depends on the Wigner-Seitz radius rs of the metallic substrate. To gain further understanding of the light–molecule/substrate interaction, we also study the bright exciton’s electron and hole densities and their interactions with infrared active vibrational modes. Our results show that (1) benzene’s bright E1 2u exciton at 7.0 eV, whose energy is insensitive to changes in rs, could be relevant for photocatalytic dehydrogenation and polymerization reactions, (2) terrylene’s bright B3u exciton at 2.3 eV hybridizes with the surface plasmon, allowing the tailoring of the excitonic energy and optical activation of a surface plasmon-like exciton, and (3) fullerene’s π ? π? bright and dark excitons at 6.4 and 6.8 eV hybridize with the surface plasmon, resulting in the tailoring of their excitonic energy and the activation of both a surface plasmon-like exciton and a dark quadrupolar mode via symmetry breaking by the substrate. This work demonstrates how a proper description of interfacial light–molecular/substrate interactions enables the prediction, design, and optimization of technologically relevant phenomena in silico.
关键词： Plasmonics,Optical Absorbance,π-conjugated molecules,Fullerene,Excitons,Hybrid Materials,Benzene,Surface Plasmonics,Magnetic,Infrared active vibrational modes,Wigner-Seitz radius,Optical,Terrylene
更新于2025-09-16 10:30:52
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D‐A Type Pendant Conjugated Molecules based on Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers
摘要： A set of fluorene-capped pendant conjugated molecules (T-m and T-p), which consist of triazine center with three carbazole substituents as the donor-acceptor (D-A) type pendant structure, were designed, synthesized and investigated as gain media for organic semiconductor lasers (OSLs). Particularly, varying the capping positions of the fluorene units onto the pendant core structures results in obviously different intramolecular charge transfer (ICT) properties, whereas T-m manifested depressed ICT characteristic and high fluorescence quantum yield. The lowest ASE threshold in neat films was recorded of 1.9 μJ/cm2 for T-m and 83.8 μJ/cm2 for T-p, respectively, which indicated that depressed ICT characteristic in the case of T-m helps to enhance the ASE properties. Remarkably, the ASE threshold remained almost unchanged and the ASE spectra showed very small shifts (within 1 nm) for T-m with film samples annealed up to 180°C in open air. In contrast, its linear counterpart 2FEtCz-m showed obviously increased ASE threshold upon annealing above 100°C. The results suggest that the selective construction of conjugated pendant molecules with depressed ICT characteristics is beneficial for finely modulating the optical and electrical properties as well as improving the thermostability and photostability, which manifests the great potentials as robust gain media for OSLs.
关键词： Organic semiconductors,Amplified spontaneous emission (ASE),Organic semiconductor lasers,Pendant conjugated molecules,Intramolecular charge transfer (ICT)
更新于2025-09-12 10:27:22
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Unraveling Correlations between Molecular Properties and Device Parameters of Organic Solar Cells Using Machine Learning
摘要： Understanding the relationships between molecular properties and device parameters is highly desired not only to improve the overall performance of an organic solar cell but also to fulfill the requirements of a device for a particular application such as solar to fuel energy conversion (high VOC) and solar-window applications (high JSC). In this work, a series of machine learning models are built for three important device characteristics (VOC, JSC, and FF) using 13 crucial molecular properties as descriptors, with an impressive predictive performance (r=0.7). These models may play a vital role in designing promising organic materials for a specific photovoltaic application with high VOC/JSC. The importance of descriptors for each device parameter is unraveled, which may assist in tuning them and improve understanding of the energy conversion process.
关键词： virtual screening,organic photovoltaics,machine learning,conjugated molecules,Organic solar cells
更新于2025-09-12 10:27:22
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Investigation of hydrogen-bonding mediated molecular packing of diketopyrrolopyrrole based donor-acceptor oligomers in the solid state
摘要： Two diketopyrrolopyrrole (DPP)-based Donor-Acceptor oligomers with thermal labile 2-methylhexyl-2-oxylcarbonyl (mHoc) groups, mHocPBT and mHocTBT, were synthesized and characterized to study the hydrogen-bonding mediated molecular packing in solid state. The soluble oligomers can be converted to strong intermolecular hydrogen-bonded and pigment-like materials HPBT and HTBT by annealing the casted solid film at a temperature between 180 and 200 °C. The formation of intermolecular hydrogen bonding significantly altered the conformation of the molecules, molecular packing structure and related optical properties of the oligomers, with HPBT molecule exhibiting bathochromic shift and HTBT molecule exhibiting hypsochromic shift on UV/Vis spectra. Spin-casted mHocTBT and HTBT films also exhibited interesting morphology and charge transport properties. Even though the single mHocTBT oligomer molecule has a better coplanar molecular conformation as compared with that of HTBT, an enhanced π-π stacking structure and larger crystal grain size rendered HTBT film better charge transport performance.
关键词： Molecular Packing,Conjugated Molecules,Hydrogen Bond
更新于2025-09-10 09:29:36