Synthesis and characterization of Y-shaped optical nonlinear chromophores with strong acceptors

Abstract

A series of Y-type chromophores L1–L3 containing bis(N,N-diethyl)aniline, bis(N-ethyl-N-phenylsilylethyl)aniline, and bis(3-phenylsilylpiperidin)aniline as electron donors, isophorone derivatives as a p-conjugated bridge, and phenyl-trifluoromethyl-tricyanofuran acceptors (CF₃-TCF) as an acceptor were synthesized and investigated. However, the introduction of stronger acceptors does not guarantee the increase of electro-optical coefficients for all the chromophores. Chromophore L1 only achieved an r₃₃ value of 110 pm V⁻¹ due to its large absorption at 1310 nm. Poled films of 100 wt% chromophores L2–L3 showed high poling efficiencies and electro-optic coefficient due to large steric hindrance and hyperpolarizability of the chromophores. An ultrahigh r₃₃ (351 pm V⁻¹ and 277 pm V⁻¹) and poling efficiency (3.50 + 0.10 nm² V⁻² and 2.63 ± 0.08 nm² V⁻²) at 1310 nm were achieved for the film containing 100 wt% chromophores L2–L3. These results indicate that the rational match between the strength of the donor, acceptor, and p-conjugated bridge plays an important role in achieving a large electro-optic coefficient.