The low energy electronic structure of poly(p-phenylene vinylene)

A two state molecular orbital model of poly(p-phenylene vinylene) (PPV) is solved using the density matrix renormalisation group method. The energies and spatial correlation functions of the low lying states are calculated. A band of tightly bound B-1(u)- excitons and a band of charge-transfer (1)A( g)(+) excitons exist below the band gap. In the limit of infinite chains, t he lowest lying B-1(u)- exciton is at ca, 2.6 eV, while the lowest lying (1 )A(g)(+) exciton is at ca. 2.9 eV. The band threshold is at 3.2 eV.