Application Of Density Functional Theory In New Solid State Hydrogen Storage Materials And Organic Solar Materials

As fossil energy is not renewable and causes serious environmental pollution,clean green energy is imminent.As a highly efficient theoretical research method,density functional theory can be used to design functional materials by means of computer simulation.It can provide valuable guidance for the study of material properties,effectively reduce experimental costs,and shorten the research period.In this thesis,solid-state hydrogen storage materials and organic solar cells are studied through density functional theory and time-dependent density functional theory.By using quasi-dynamic simulations,solid-state hydrogen storage technology using POSS is predicted.By considering the influence of microstructure on the photoelectric conversion efficiency of organic solar cells,we investigate the organic solar cells SubPc/C70.The following innovative research results have been obtained:（1）We have systematically studied four cages of T8,T10,and T12(D_2d and D_6h)for hydrogen storage including adsorption and encapsulation of hydrogen molecules by density functional theory.We compare their specific surface area and ability of hydrogen adsorption onto four cages.We find that oxygen atoms of silsesquioxane cages and the face center are main adsorption points.In addition,we use quasi-dynamic method to study the encapsulation of hydrogen molecules into these cages because of the timescale limitation of ab initio molecular dynamics.Thermodynamic parameters such as enthalpy and Gibbs free energy at different temperatures are calculated during the insertion processes.We find that the insertion process of hydrogen molecule into T12(D_6h)cage is almost energy conserved and its energy barriers of enthalpy and free energy are moderate at standard conditions.T12(D_6h)cage has much lower energy barrier for hydrogen insertion than other three cages in all temperature ranges,we obtain the energy barrier13.2 kJ/mol using transition state theory,the SSA of T12(D_6h)is 4093.3 m²/g,and the gravimetric density is 7.55 wt%,the averaged binding energy is 0.05 eV per hydrogen molecule.In addition,T12(D_6h)can also package a H₂ molecule inside,it is an ideal hydrogen storage material.our work provides a valuable reference for new hydrogen storage materials.（2）We perform a theoretical investigation utilizing density functional theory（DFT）and time-dependent functional theory（TDDFT）to study the relationship between morphology and some key properties of SubPc/C70 solar cells.We stuty the influence of SubPc/C70 configurations in condensed phase,investigate the influence of different molecular arrangements and orientations on open circuit voltage of SubPc/C70 solar cell and ground state electronic structure as well,and also understand how the molecular arrangements and orientations impact electronic absorption spectrum of SubPc/C70 at the interface,including absorption wavelength and oscillator strength.We employ long range corrected density functionals with a polarizable continuum model to study SubPc/C70different configurations in condensed phase.By modeling different SubPc/C70configurations in condensed phase（“bed”configurations,“umbrella”configurations）,our calculated results,obtained with long range corrected density functional plus integral equation formalism variant polarizable continuum model,show the change of Voc can be up to 0.45 V and the absorption strength in visible region can be doubled due to the modification of configuration.We find that B-P configuration has the largest open circuit voltage,and B-V configureation has the best ability of photon absorption and,which both significantly influence the open circuit voltage and UV-vis absorption spectrum of subPC/C70 solar cell,among the modeled configurations.In addition,our results show that the most stable configuration U-V is a bad choice considering the strength of photon absorption and open circuit voltage in subPC/C70 solar cell.To study the effect of microscopic configuration between donor and receptor in organic solar cells,which can provide reference for designing organic solar cells and improving photoelectric conversion efficiency of organic solar cells.