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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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Searching the crystal structure of silicon using the generalized scaled hypersphere search method with the rapid nuclear motion approximation
摘要： The scaled hypersphere search method with the rapid nuclear motion approximation was applied for the prediction of the crystal structure of silicon. Five well-known structures and one novel structure were found. The space group of the novel structure found is Imma. By comparing this with the two known silicon structures in the same space group, it is found that one of these well-known Imma structures and the novel Imma structure are similar. According to our ab initio calculations based on the projector augmented wave method with the Perdew–Burke–Ernzerhof functional, the novel structure is a semiconductor, with calculated band gap 0.89 eV.
关键词： scaled hypersphere search method,crystal structure prediction,silicon,semiconductor,rapid nuclear motion approximation
更新于2025-09-23 15:19:57
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Topochemical Path in High Lithiation of MoS <sub/>2</sub>
摘要： Lithiation of MoS2/RGO (reduced graphite oxide) electrodes repeatedly reached experimental capacities larger than 1000 mA·g–1, corresponding to at least 6 lithium equivalents per gram of MoS2. At our best knowledge, a convincing explanation is still missing in literature. In most cases, phase separation into Li2S and elemental Mo was assumed to occur. However, this can only explain capacities up to 669 mA·g–1, corresponding to an exchange of four Li. Formation of LiMo alloys could resolve the problem but the Li/Mo system does not contain any binary phases. If signs for Li2S formation were found, indeed experimental capacities were below 700 mAh·g–1. Here we present a topochemical mechanism, which sustains multiple charge/discharge cycles at 1000 mAh·g–1, corresponding to an exchange of at least 6 Li per formula unit MoS2. This topochemical reaction route prevents decomposition into binary phases and thus avoids segregation of the components of MoS2. Throughout the whole lithiation/delithiation process, distinct layers of Mo are preserved but extended or shrunk by slight movements and reshuffling of sulfur and lithium atoms. On addition of 6 Li per formula unit to MoS2, all central sulfur atoms are hosted in mutual Mo–S layers such that formal S2– and Mo2– anions appear coordinated by lithium cations. Indeed, similar structures are known in the field of Zintl phases. Our first-principles crystal structure prediction study describes this topological path through conversion reactions during the lithiation/delithiation processes. All optimized phases along the topological path exhibit a distinct Mo layering giving rise to a series of dominant scattering into pseudo 001 reflections perpendicular to these Mo planes. The mechanism we present here explains why such high capacities can be reached reversibly for MoS2/RGO nano composites.
关键词： topological path,Crystal structure prediction,Total energy calculations,MoS2,Li-Mo-S ternary phases,Li-ion battery,Lithium
更新于2025-09-23 15:19:57
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Theoretical study on the charge transport properties of three series dicyanomethylene quinoidal thiophene derivatives
摘要： It is very important to analyse the most advantageous connection style for quinoidal thiophene derivatives, which are used in n-type organic semiconductor transport materials. In the present work, the charge transport properties of three series of quinoidal thiophene derivatives, oligothiophene (series A), thienothiophene (series B) and benzothiophene (series C), are systematically investigated by employing the full quantum charge transfer theory combined with kinetic Monte-Carlo simulation. The single crystal structures of the molecules we constructed were predicted using the USPEX program combined with density functional theory (DFT) and considering the dispersion corrected. Our theoretical results expounded that how the different connection styles, including oligo-, thieno-, benzo- thiophene in the quinoidal thiophenes derivatives, effectively tune their electronic structures, and revealed that how their intermolecular interactions affect the molecular packing patterns and hence their charge transport properties by symmetry-adapted perturbation theory (SAPT). In the meanwhile we also elucidated the role of end-cyano groups in noncovalent interactions. Furthermore, it is clarified that the quinoidal thiophene derivatives show excellent carrier transport properties due to their optimal molecular stacking motifs and larger electronic couplings besides low energy gap. In addition, our theoretical results demonstrate that quinoidal oligothiophene derivatives (n=3~5) with more thiophene rings will have ambipolar transport properties, quinoidal thienothiophene and benzothiophene derivatives should be promising alternatives as n-type OSC. When we focused only on the electronic transport properties in the three series of molecules, quinoidal benzothiophene derivatives are slightly better than quinoidal oligothiophene and thienothiophene derivatives.
关键词： Crystal structure prediction,Dicyanomethylene quinoidal thiophene,N-type and ambipolar organic semiconductors,Charge transport property,Intermolecular interactions
更新于2025-09-19 17:15:36