Theoretical Study on One‐ and Two‐Photon Absorption Properties of PPV Derivative with Electron‐Donor Phenylanthracene as Pendent Group

Based on the equilibrium structures from quantum mechanics AM1 method, employing INDO/CI method and the sum‐over‐state (SOS) formula, the one‐photon absorption (OPA) and two‐photon absorption (TPA) properties as well as the second hyperpolarizabilities were discussed in detail for a kind of PPV derivative poly 2‐(9‐phenylan‐ thracen‐10‐yl)‐1,4‐phenylenevinylene ( P1 ). The results indicate that the two‐photon cross section ( δ ) increases with the increasing of the number of repeating segment ( n ), however only a slight increase corresponds to the increasing of molecular weight when the repeating unit number arrives at a certain number. From this point of view, the TPA cross section values of P1 were extrapolated through the linear fit of δ value vs. 1/ n . The δ value of P1 is as high as 181 GM (1 GM10 −50 cm 4 ·s·photon −1 ). Concerning the influence of pendent group and extension of π‐conjuga‐ tion on δ values, another four oligomers P2 , PPV , P1‐1 , and P2‐1 were investigated for comparison. The calculation results reveal that the position and property of pendent group have great influence on the OPA and TPA properties. A most crucial role for relatively larger δ value was played by the extension of π‐conjugation.