cm9b00546_si_001.pdf (1.85 MB)
Impact of Atomistic Substitution on Thin-Film Structure and Charge Transport in a Germanyl-ethynyl Functionalized Pentacene
journal contributionposted on 2019-05-08, 00:00 authored by Jeni C. Sorli, Qianxiang Ai, Devin B. Granger, Kaichen Gu, Sean Parkin, Karol Jarolimek, Nicholas Telesz, John E. Anthony, Chad Risko, Yueh-Lin Loo
Functionalization of organic semiconductors through the attachment of bulky side groups to the conjugated core has imparted solution processability to this class of otherwise insoluble materials. A consequence of this functionalization is that the bulky side groups impact the solid-state packing of these materials. To examine the importance of side-group electronic character on accessing the structural phase space of functionalized materials, germanium was substituted for silicon in triisopropylsilylethynylpentacene (TIPS-Pn) to produce triisopropylgermanylethynylpentacene (TIPGe-Pn), with the TIPGe side group comparable in size to TIPS, but higher in electron density. We find TIPGe-Pn single crystals exhibit slip-stack, herringbone, and brickwork packing motifs depending on growth conditions, a stark contrast to TIPS-Pn, which accesses only the brickwork packing motif in both single crystals and thin films. Polycrystalline thin films of TIPGe-Pn exhibit two new, unidentified polymorphs from spin-coating and postdeposition annealing. Our experiments suggest that access to the structural phase space is not guided solely by the size of the side group; the electronic character of the side group in functionalized compounds also plays a significant role. As such, simple atomistic substitutions can cause significant differences in the accessible solid structures.