Characterizing Interesting Chromophores with Ultrafast Investigations

Abstract

Ultrafast spectroscopy has made important fundamental contributions to multiple fields of science despite its relatively young age. Its unmatched ability to probe dynamics of electronic excited states on a femtosecond timescale has vastly expanded understanding of solvation dy- namics, rates of electron transfer, the photophysics of transition metal complexes, and more that are not mentioned here. Fundamental insights will remain important for understanding new, unexpected behavior as previous findings manifest themselves in applications with more complex structures and mechanisms. Ultrafast spectroscopy is well-suited to investigate new materials and phenomena on a such a level and help guide future studies, as this thesis hopes to accomplish. It will be divided into 4 chapters. Chapter 1 will serve as an introduction tothe field and introduce background material important work within to this thesis. Focus is placed on the ultrafast, time-resolved techniques studied and employed in the work. Chapter 2 is a summary of work pertaining to uncovering symmetry-breaking charge transfer (SBCT) in a nonfullerene acceptor, IDTBR. Background is provided about organic photovoltaics and SBCTs before reviewing results and discussion. Despite displaying signatures of SBCT in nar- rowband and broadband TA, a confident assignment, a fully confident assignment is yet to be made. SBCT in the film phase could possibly assist important intermolecular coupling. Chap- ter 3 contains a report of the isolation and characterization of a series of singly-reduced iridium chromophores. Key findings include instability to polar solvents and an excited state lifetime below 25 ps, both incompatible with previous understanding. Despite the nigh-impossible diffusion-limited pathway, reactivity with chloro- and bromobenzene was displayed. Chapter 4 serves as a conclusion and look forward at the role of ultrafast spectroscopy in the fields of each project.