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

Abstract

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 of 1000 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.

Thickness-dependent exciton relaxation dynamics of few-layer rhenium diselenide

“…The resolution-limited enhancement of ∆T signal before 0 delay is caused by the carrier thermalization via carrier-carrier scattering and carrier-phonon scattering, [28] which rapidly expands the photoexcited carriers from the highenergy state toward the bottoms of energy bands, and es-tablishing a quasi-equilibrium distribution for the formed hot carriers. [29] To analyze the subsequent relaxation process, the time-resolved curves are fit to a bi-exponential function as follows:…”