Control of Molecular Orientation in Organic Semiconductors Using Weak Iodine–Iodine Interactions

Controlling the molecular orientation of materials is a key issue for improving the performance of organic semiconductor devices. Herein, we demonstrate the structure–property relationships of iodinated and noniodinated molecules based on an asymmetric thienoacene framework. The noniodinated molecule formed an antiparallel slip-stack structure with small orbital overlap between molecules. In contrast, the iodinated molecule formed a head-to-head layered-herringbone structure, and as a result, the transfer integrals became larger and the hole mobility increased significantly compared with the noniodinated material. The iodinated molecule was made into a stable and solution-processable p-type organic semiconductor with a mobility of 2.2 cm2 V–1 s–1, which was 2 orders of magnitude higher than that of the noniodinated molecule. This study reveals that controlling molecular orientations using iodine–iodine interactions is a promising strategy for accelerating the development of organic semiconductor materials.