End-capped engineering of truxene core based acceptor materials for high performance organic solar cells: theoretical understanding and prediction

Abstract

As the end-capped engineering plays a key role in enhancing the photovoltaic characteristics of non-fullerene acceptors for organic solar cells, therefore, the present study was aimed to develop some novel materials with excellent photovoltaic properties using end-capped acceptors engineering. For this purpose, five new molecules (S1-S5) were designed by end-capped engineering of acceptor moiety of reference Tr(Hex)6Cl (R) keeping the truxene core and thiophene π bridge same. Among different density functional theory (DFT) based functionals, B3LYP in conjunction of 6-31G(d,p) basis set of DFT was found in good agreement of experimental data and the most suitable basis set for determining the optoelectronic properties. All the designed molecules (S1-S5) illustrated greater absorption maxima (red shift), reduced energy gap and smaller excitation energy values as compared to R. Among all the studied molecules (R and S1-S5) the highest stabilized highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were observed for S1 which is due to the presence of strong electron withdrawing end capped moiety E1 which contain dicyano groups. The smaller reorganizational energy value of electron and holes proved designed molecule S1 as a better candidate for charge transfer as compared to other molecules. All the designed molecules exhibited better charge transfer properties and greater electron coherence in acceptor moiety as compared to R. Overall results of present study depicted that all the end capped acceptors (E1-E5) of designed molecules (S1 to S5) possessed efficient electron withdrawing properties. These results indicate that all star-shaped conceptual molecules (S1-S5) are ideal aspirants for construction of future organic solar cells.