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Chi W.-J.,Beijing Institute of Technology | Chi W.-J.,Key Laboratory of Cluster Science of Ministry of Education | Li Z.-S.,Beijing Institute of Technology | Li Z.-S.,Key Laboratory of Cluster Science of Ministry of Education | And 2 more authors.
Physical Chemistry Chemical Physics

The electronic structures, optical properties and hole mobilities of 4-(4-phenyl-4- α-naphthylbutadieny)-triphenylamine and its five derivatives are investigated by density functional theory (DFT). The results show that the highest occupied molecular orbital (HOMO) of all molecules is almost fully delocalized throughout the whole molecule, and the substituents -N(CH3)2 and -C6H5 denoted as molecules 6 and 2, respectively, have the largest contribution to the HOMO, which is favorable for hole transfer integral and hole mobility. Spectrum analysis indicates that all molecules have large Stokes shifts based on absorption and emission spectra. In addition, it is found that the hole reorganization energy of all molecules is about 0.5 times compared to that of electrons, which implies that hole mobility is bigger than electron mobility. On the basis of predicted packing motifs, the hole mobilities (u) of all molecules are also obtained. The largest hole mobility of molecule 2 (0.1063 cm2 V-1s-1) is found to be higher than that of other molecules due to the face-to-face stacking mode, which suggests that -C6H5 is a good substituent group for improving hole mobility compared to other electron releasing groups. We hope that our results will be helpful for the further rational molecular design and synthesis of novel hole transport materials (HTMs) for high performance perovskite-type solar cells. © the Owner Societies 2015. Source

Sun Z.-Z.,Key Laboratory of Cluster Science | Sun Z.-Z.,Beijing Institute of Technology | Zheng K.-M.,Key Laboratory of Cluster Science | Zheng K.-M.,Beijing Institute of Technology | And 6 more authors.
RSC Advances

Density functional theory (DFT) calculations were carried out to explore the effects of chemically modifying the polypyridine ligands and design efficient Co-based redox mediators for dye-sensitized solar cells (DSSCs). Our results showed that the redox properties of cobalt complexes can be well tuned by altering the number and position of nitrogen atoms on the ligand ring. Adding oxygen atoms on the ligand ring will evidently increase the redox potential, which might be unfavorable for the dye regeneration. The designed good redox mediators possess similar redox potential and reorganization energy to the current high-efficiency redox couples, thus are promising to be used in prospective DSSCs. © 2014 the Partner Organisations. Source

Hao X.,Beijing Key Laboratory for Chemical Power Source and Green Catalysis | Zhu J.,Northwestern University | Jiang X.,Beijing Key Laboratory for Chemical Power Source and Green Catalysis | Wu H.,Beijing Key Laboratory for Chemical Power Source and Green Catalysis | And 6 more authors.
Nano Letters

Polymeric nanomaterials emerge as key building blocks for engineering materials in a variety of applications. In particular, the high modulus polymeric nanofibers are suitable to prepare flexible yet strong membrane separators to prevent the growth and penetration of lithium dendrites for safe and reliable high energy lithium metal-based batteries. High ionic conductance, scalability, and low cost are other required attributes of the separator important for practical implementations. Available materials so far are difficult to comply with such stringent criteria. Here, we demonstrate a high-yield exfoliation of ultrastrong poly(p-phenylene benzobisoxazole) nanofibers from the Zylon microfibers. A highly scalable blade casting process is used to assemble these nanofibers into nanoporous membranes. These membranes possess ultimate strengths of 525 MPa, Young's moduli of 20 GPa, thermal stability up to 600 °C, and impressively low ionic resistance, enabling their use as dendrite-suppressing membrane separators in electrochemical cells. With such high-performance separators, reliable lithium-metal based batteries operated at 150 °C are also demonstrated. Those polyoxyzole nanofibers would enrich the existing library of strong nanomaterials and serve as a promising material for large-scale and cost-effective safe energy storage. © 2016 American Chemical Society. Source

Liu Q.,Key Laboratory of Cluster Science of Ministry of Education | Liu Q.,Beijing Institute of Technology | Li Q.-S.,Key Laboratory of Cluster Science of Ministry of Education | Li Q.-S.,Beijing Institute of Technology | And 13 more authors.
Theoretical Chemistry Accounts

By means of density functional theory calculations, the adsorption process of I2 at Pt (111) surface in dye-sensitized solar cells (DSSCs) has been investigated. The obtained adsorption energies and stable structures depending on the adsorption sites of the Pt surface are in good agreement with experimental values. Our results show that the dissociative chemisorption and the non-dissociative chemisorption are competitive for the adsorption of I2 on the Pt surface, and the dissociative pathway is more favored in energy. This study is expected to enrich the understanding on the origin of the excellent heterogeneous catalytic performance of Pt for triiodide reduction and the complex iodine chemistry in DSSCs. Understanding of this adsorption mechanism is helpful for rational screening for redox couple and the Pt-free alternative counter electrode materials. © Springer-Verlag Berlin Heidelberg 2013. Source

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