| With the rapid growth of energy demand and concomitant challenges for equitable climate protection in modern society,there is a constant need to develop green and sustainable energy.Solar energy,as renewable energy,has the advantages of environment-friendly and sustainable for utilization,and its exploitation and research have been a subject of intense:interest.Here several kinds of dye molecules and Si-based low-dimensional nanomaterials have been designed and characterized,based on extensive theoretical calculations and ab initio molecular dynamics simulations.Their structures,stabilities,photoelectric properties and potential applications in optimal utilization of solar energy and development of high-performance lithium ion batteries,have been discussed.The main research contents and results are summarized as follows:(1)Motivated by the newly-synthesized osmacyclic complexes,theoretical calculations have been employed to explore electronic and optical properties of osmium-bridged tricyclic aromatic compounds.Considering the direction of charge transfer,the steric effect of triphenylphosphine groups,and the features of frontier orbitals of these osmacycle derivatives,the optimal positions for introduction of different π-bridge groups have been determined,and several D-π-A dye molecules with the carboxyl group as an anchor have been constructed.The present calculations show that such newly-designed molecules by introducing thiophene and thienothiophene units into the bridge show very strong and broad adsorptions in the whole visible region and excellent charge separation in the first excited state of 1(ππ*)from the HOMO-LUMO excitation.Furthermore,the predicted relatively high light harvesting efficiency and large driving force for the electron injection suggest that they are quite promising for design of high-performance dye-sensitized solar cells.(2)Based on the recently-synthesized tetraethynylsilane molecule,a diamond-like Si(C≡C)4 crystal material has been envisaged and constructed.Ab-initio molecular dynamics simulations and first-principles calculations show that the semiconductor material has high thermal stability.The properties of band structure,absorption spectrum,density of states,electronic transport,and mechanical parameters have been investigated as well.The calculations reveal that the through-space conjugation among the d orbitals of Si and the π*orbitals of ethynyl moieties can remarkably enhance the photoconductivity.Furthermore,this new-type superlight and super-flexible semiconductor is predicted to have unique electronic,optical,and mechanical properties,and it is quite promising material for the high-performance UV optoelectronic devices suitable for various practical demands in a complex environment(3)Extensive density functional theory calculations have been performed on the ptSi C12H8Si molecule and its resultant 2D SiCs siligraphene periodic system.The molecular planarization of C12H8Si can remarkably lower the energy levels of LUMO and LUMO+1 and substantially enhance its electron-storage ability.The stabilization of ptSi-C12H8Si can be realized by capturing four electrons.Alternatively,the ptSi-C12H8Si molecule can easily accommodate four lithium atoms,yielding a stable and nonmagnetic ptSi-C12H8Si-Li4 complex with novel properties for Li adsorption and Li+desorption.Based on the ptSi SiC12 building block,a newly-designed SiC8 siligraphene 2D network containing ptSi has been constructed,and it was predicted to have high thermal stability,good conductivity,and strong electron-storage ability with a theoretical capacity of 1297 mAh/g.The predicted relative energy profiles for Li and Li+ diffusions on the 2D ptSi SiC8 sheet show the Li intercalation and Li+ dissolution is quite facile.Such novel structural and electronic properties of the SiC8 siligraphene containing ptSi are highly required for a promising anode,and these results open up an avenue to develop new electrode materials for the high-performance LIBs. |
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