In collaboration with the Klausen lab at JHU we are investigating the photophysics of novel classes of organosilanes (including symmetrically (Sins) and asymmetrically (Sina) functionalized silane chains) that exhibit promising photoinduced charge-transfer behavior for optoelectronic applications. Using a combination of Transient Absorption (TA) and Femtosecond Stimulated Raman Spectroscopy (FSRS) we have demonstrated that ultrafast asymmetric dipolar electron transfer occurs between the electron rich silane core and pendant organic acceptors and is attributed to molecular asymmetry associated with silane chain conformation. The rate of charge recombination increases as the donor chain length is increased and is highly sensitive to local solvent polarity. These behaviors can be attributed to a “gap-law” dependence of the recombination rate. We are continuing to explore how structure, including silane conformation, and local environment can be used to control charge separation lifetimes as needed to optimize material properties, including non-linear susceptibilities, optical gating of material charge polarization, and photovoltaic potential.
The Bragg Lab > Photoinduced charge separation in hybrid σ-π conjugated organosilanes