Modulation of two donors at different sites of the thiophene conjugate bridge for enhancing the electro-optical properties of dual-donor chromophores

We successfully synthesized and systematically investigated novel chromophores Y1, Y2, and Y3 with a dual-donor structure. By adjusting the electron-donating groups at different positions (C3 and C4) of thiophene, we optimized the electro-optical properties of the chromophores. We have optimized thenonlinear optical properties of the chromophores Y1 and Y2, which work with the common FTC hosts, incorporated additional electron-donating groups (DEA) at positions 3 and 4 of thiophene, respectively. At a doping concentration of 20 %, the r33 values for FTC/APC Y1/APC and Y2/APC were 21 pm V−1, 56.2 pm V−1, and 5.8 pm V−1. This indicates that introducing the donor group at positions 2 and 3 of thiophene is more favorable than positions 3 and 4 (Y1 > Y2). And we successfully synthesized Y3 by replacing DEA with a julolidine moiety. At a doping concentration of 30 %, Y3/APC had the greatest r33 of all values at 153.3 pm V−1. This demonstrates that introducing DEA at the 3 positions of thiophene in FTC effectively enhances the electron-donating ability, and the additional donor moiety acts as an isolated group, effectively reducing intermolecular dipole-dipole interactions. Furthermore, Y3, with julolidine as the donor group, exhibits stronger electron-donating ability, ultimately leading to enhanced macro EO activity. These findings highlight the potential application of these novel chromophores for potential applications in optoelectronic devices.