Correlated theory of triplet photoinduced absorption in phenylene-vinylene chains

In this paper, the results of large-scale correlated calculations of the triplet photoinduced-absorption (PA) spectrum of oligomers of poly-(para)phenylenevinylene (PPV) containing up to five phenyl rings are presented. In particular, the high-energy features in the triplet PA spectrum of oligo-PPV's are the focus of this study, which, to our knowledge, have not been investigated theoretically or experimentally. The calculations were performed using the Pariser-Parr-Pople model Hamiltonian and many-body effects were taken into account by means of the multireference singles- doubles configuration-interaction procedure without neglecting any molecular orbitals. The computed triplet PA spectrum of oligo-PPV's exhibits rich structure consisting of alternating peaks of high and low intensities. The predicted higher-energy features of the triplet spectrum can be tested in future experiments. Additionally, theoretical estimates of exciton binding energy are also presented