Computational modeling of isoindigo-based polymers used in organic solar cells

We report a computational modeling investigation, based on DFT and TDDFT calculations, on the structural, electronic, and optical properties of three prototypical donor-acceptor polymers based on the isoindigo unit acceptor moiety, namely, PTI-1, PBDT-I, and PBDT-TIT, in order to calibrate a computational protocol to screen new candidate polymers and to get a better understanding of the properties of the investigated series. Starting from the monomeric units and by using a growing-up approach, we were able to reproduce the experimental electrochemical and optical properties and to estimate the effective conjugation length of these polymers. This study can support the choice of suitable donor and acceptor building blocks and provides the computational framework for an in silico screening of new target photoactive polymeric systems.