The ALMO Method Is Used To Calculate The Exciton Dissociation Energy And External Recombination Energy Of Organic Photovoltaic Materials

The dissociation energy and charge carrier mobility of the charge transfer state exciton are important factors restricting the conversion efficiency of the organic solar cell.However,the research on the dissociation energy of the exciton is still insufficient;the study of the carrier mobility is more Calculating rate constants based on the classical Marcus charge transfer rate equation does not correctly explain the carrier mobility in certain materials at low temperatures.To use Marcus theory at low temperatures,it is necessary to use external recombination energy calculations.Therefore,in this paper,the effect of exciton dissociation energy and the external recombination energy in the charge transfer process have been studied using the absolutely-localized molecular method(ALMO)method to design organic solar cells with small dissociation energy and external reorganization energy.The material has a theoretical reference.The specific research content of this paper includes the following two parts:1.The dissociated energy(ECT diss)of charge-transfer state at the DA interaction is a crucial parameter to determine the efficiency of organic solar cells.The ?SCF-liked ALMO combining with DFT is applied to investigate ECT diss of the lowest CT at the oligoacenes/C60 interfaces.ALMO computed CT energies behave a correct 1/d asymptotic feature and almost exchange-correrlation(XC)functional independent character.ALMO coupled with polarizable continuum model provide a nice method to study the electrostatic polarization of CT in organic solids.The results of dissociation energy of CT demonstrate that increasing the conjugation-length,high-dielectric constant,and adjusting molecular packing to control the polarization effect are effective methods to dissociate the lowest CT into free electron and hole carriers.2.Using non-equilibrium solvation model combined with ALMO method,the external reorganization energy,polarization energy,FMO energy level and bandgap of naphthalene,perfluoro-naphthalene,pentacene and perfluoropentacene were calculated.In addition,the rule of the external reorganization energy of the fullerene(A)and pentacene(D)systems with different intermolecular distances under different configurations was studied;the influence of the conjugation length on the reorganization energy and the pentacene crystals were different and the external reorganization energy of the transport channels.The results show that for naphthalene(perfluoronaphthalene)and pentacene(perfluoropentacene),the external reorganization energy and polarization energy have the same tendency,and the introduction of electron-withdrawing groups in the system can change the loading.The transport properties of the dyestans;compared with the face-on configuration,the external reorganization energy of the system in the edge-on configuration is more pronounced due to the large polarization component in the direction of the molecular skeleton and the change in intermolecular distance;in pentacene In crystals,the external reorganization energy of different transport channels(the spatial arrangement of molecules is determined)is also different.The above studies suggest that when designing photovoltaic materials,it is possible to obtain characteristic materials that are conducive to increasing carrier mobility by taking control of substituents and crystal morphology.