Improved electro-optical property by introducing stronger acceptor to thermal stable chromophores using modified julolidine as donor

摘要

Two novel second order nonlinear optical chromophores based on large steric hindrance group modified julolidine donor and CF3-Ph-TCF acceptor linked via thiophene bridge were synthesized and characterized. Density functional theory (DFT) calculations suggested that the molecular quadratic hyperpolarizability (beta) value of CF3Ph-TCF based chromophore is 18.1% and 18.8% larger than that of TCF based chromophores, respectively. The optimized structure shows that chromophore z4-3f with stronger acceptor and larger modification group presents the best molecular configuration. UV-Vis results show great red-shift about 130 nm for chromophores z2-3f and z4-3f compared with z2 and z4. According to cyclic voltammetry measurements, chromophores z2-3f and z4-3f showed lower energy gap indicating better intramolecular charge-transfer (ICT) transition. Especially, chromophore z4-3f displayed good thermal stability with onset decomposition temperature at about 265 degrees C. The poled films containing 25 wt% chromophores in amorphous polycarbonate (APC) afforded electro-optical(EO) coefficients (r(33)) of 125 and 128 pm/V at 1310 nm. Further, film containing larger group modified chromophore was more efficient to realize good EO property with an order parameter (45) up to 18.4%. Ws confirmed that chromophores z2-3f and z4-3f, which had good thermal stability and high r(33) values after poling in films, was a promising candidate for practical use.