Theoretical Investigations Of Conformation And Charge Transfer Properties Of Several Kinds Of Materials For Organic Solar Cells

In this thesis,we have considered 6 kinds of naphthalimides-based small molecules and polymer MDMOPPV as research objects,then investigated their structural properties,aggregation properties,absorption properties and charge transfer properties.With the results we got,we try to find the mechanism that how the properties of materials that influence the efficiency of organic solar cells and finally provide theoretical guidance for the organic synthesis.The details are as follows:(1).First we optimized the geometry of 6 naphthalimides-based molecules.We find that there are many potential wells for these Polycyclic Aromatic Hydrocarbon Molecules.We can hardly get the real structure with minimum energy with the help of Gaussion.And if we want to optimize the geometry of polymer,the situation may become even worse.In order to solve this problem,we chose molecular dynamics simulations to simulate the structure of MDMOPPV.During the period we investigated the aggregation process and the aggregation properties,we have fitted a new OPLA-AA force field,we have also discussed how the solvent influence the radial distribution function,solvation energy,mean square displacement and radius of gyration.Finally,we find that when we solvates MDMOPPV with chlorobenzene(CB),chloroform(CF)and methyl alcohol(MA),the MDMOPPV-CB solution has the largest solvation energy,which means that CB is a better solvents for MDMOPPV than CF and MA.The polarity of solvents also has distinct impacts on the radius of gyration,the stronger the polarity,the shorter the radius of gyration.For MDMOPPV,it has the largest mean square displacement in MA,however,when MDMOPPV solvates with CB,we can find a noticeable decrease for the mean square displacement compare to solvating,with MA.(2).We have caleulated the organization energy,driving force and coupling of 6 naphthalimides-based acceptors for organic solar cells of both D*A?D+A-process and DA*?D+A-process,with the help of semielassical Macus Theory,we predicted their charge transfes velocity constants.We have also calculated the absorption spectra of all molercules.From the results,we find that electronic-withdi awing side groups have great impacts on the photoelectrical properties of the molecules.First,electronic-withdrawing side groups may result in lower energy of LUMO orbit,what's more,the energy of LUMO orbit t of the side group of acceptors decrease along with he electronegativity of side groups.Second,the electronic-withdrawing side groups may cause the localization of Charge distribution of backbones,which then increase the conversion energy between neutral molecules and anion molecules,and finally increase the reorganization energy.Third,if we add an electronic-withdrawing side group on the backbone,the position of the Maximum absorption peak does not charge,but the intensity increases.However,if we add an electron-donating group on the backbone,the absorption spectra will shift towards the longer wavelength side and the intensity of the Maximum absorption peak will decrease at the same time.