Donor strengthening strategy for FTC-based organic nonlinear chromophore

The molecular chromphores with high first hyperpolarizability values have been reported with the development of conjugated polyene-bridge or thiophene-bridge system and strong tricyano-containing heterocyclic electron acceptors. In this work, we investigated the enhancement of the electro-optic response by introducing various groups, such as OCH3, Ophenel, OTBDMS, etc, as an additional donor part on conventional FTC type donor-π-acceptor molecules. These new type donors exhibited a strong solvatochromic effect, indicating an extra donation to the pi-conjugated bridge, which shifted the charge-transfer absorption of the chromophores to the lower energy region. Furthermore, the simple modification on the donor moiety resulted in a great improvement in the first hyperpolarizability and macroscopic electro-optic coefficient (r ₃₃) over the benchmark dialkylamino FTC counterparts. For the real applications, the stronger acceptor was adopted to further increase the r ₃₃ and such a chromophore was post-functionalized as side-chain polymer to enhance the temporal stability.