Diketopyrrolopyrrole based highly conjugated small molecules for organic solar cells

A series of three donor molecules (DPP-B, DPP-N and DPP-P) based on diketopyrrolopyrrole (DPP) sharing the similar backbone of D-π-A-π-D have been investigated. In these molecules, substituents such as pyrene, naphthalene and benzene act as the electron donating end groups, DPP as the central core unit and thiophene has been used as a bridge between donor and acceptor fragments. Theoretical calculations have been carried out with the help of density functional theory (DFT) and time-dependent functional theory (TD-DFT). For the optimization of geometry of investigated molecules, DFT functional B3LYP/6-31g(d) has been used and TD-B3LYP/6-31g(d) has been used to obtain the best results of calculations inexcited state. DPP-P has been considered a suitable donor molecule among all investigated molecules as it manifests the suitable value of Eg of 2.24 eV and showed the stronger absorption λmaxof 611 nm. Hence, this study reveals that investigated donor molecules are suitable for high performance organic solar cell devices