Leveling up Organic Semiconductors with Crystal Twisting

Abstract

The performance of crystalline organic semiconductors depends on the solid-state structure, especially the orientation of the conjugated components with respect to device platforms. Often, crystals can be engineered by modifying chromophore substituents through synthesis. Meanwhile, dissymetry is necessary for high-tech applications like chiral sensing, optical telecommunications, and data storage. The synthesis of dissymmetric molecules is a labor-intensive exercise that might be undermined because common processing methods offer little control over orientation. Crystal twisting has emerged as a generalizable method for processing organic semiconductors and offers unique advantages, such as patterning of physical and chemical properties and chirality that arises from mesoscale twisting. The precession of crystal orientations can enrich performance because achiral molecules in achiral space groups suddenly become candidates for the aforementioned technologies that require dissymetry.

Polymer-Assisted Polymorph Transition in Melt-Processed Molecular Semiconductor Crystals

“…The observed optical activity of banded spherulites arises not from the molecular or crystal structure, but rather from the splaying of anisotropic crystalline lamellae in thin films as they twist about the growth direction . We have recently observed similar behavior in banded spherulites of other achiral molecular semiconductors, such as tetrathiafulvalene , and 2,5-bis­(3-dodecyl-2-thienyl)-thiazolo­[5,4- d ] thiazole . The spherulite sends as few as 4 and as many as 10 angular domains that are alternately left- and right-handed.…”