Tuning the Transparency and Exciton Transition of D-π-A-π-D Type Small Molecules

Organic small molecules possess significant potential for semitransparent optoelectronic applications due to their tunable optical properties and inherent transparency. However, tailoring these materials is challenging as their optoelectronic properties are sensitive to subtle structural changes, compounded by the existence of over a million potential structural designs. To address these complexities, we present a material discovery workflow that combines literature-based molecule preselection with TDDFT calculations, creating customized small molecule structures with adjustable transparency windows. We identified fifty-four small molecules with a D-π-A-π-D architecture, incorporating nine central (A) and six end (D) units connected by a thiophene π-bridge. Through TDDFT calculations, we determined the theoretical absorption spectra and energy levels of the identified molecules. Ultimately, we synthesized twenty-four molecules that exhibit promising transparency properties by selectively absorbing photons in the ultraviolet (UV) and near-infrared (NIR) regions, with a significant optical transmission band relevant to the visible spectrum, which we will refer to as "optical window". Characterization of the resultant small molecules revealed that six of them, in particular, exhibited selective absorption with the broadest "optical window". We believe that our study will provide valuable insights to establish an effective material discovery workflow for highly transparent conjugated organic small molecules.