Modulation and mechanism of ultrafast transient spectroscopy based on dimethylamino-carbaldehyde derivatives

Two dimethylamino-carbaldehyde derivatives with different π-bridge lengths were prepared, and their transient optical properties and photophysical mechanisms were investigated by transient absorption spectroscopy and Z-scan measurements. Owing to the difference in molecular structures, the two compounds exhibit different populations of locally excited states and, therefore, they also produce different transient absorption spectra. After photoexcitation, both molecular materials exhibit a wide excited state absorption band from 450 nm to 1000 nm. Meanwhile, the excited state lifetimes are dramatically different, 2 ns and 100 ps, for the two molecules. A figure of merit greater than 2 at the wavelength of1000 nm is obtained. The results show that modulating the population of the locally excited states in this type of molecule can be a promising approach for obtaining optical switching and solar cell materials.