Design, Synthesis, and Versatile Processing of Indolo[3,2-b]indole-Based π-Conjugated Molecules for High-Performance Organic Field-Effect Transistors

A series of indolo[3,2-b]indole (IDID) derivatives comprising the core unit of N,N-dihexyl-IDID with different aromatic and aliphatic substituents at 2- and 7-position are designed and synthesized to construct high-performance organic semiconductors by different processing routes. Structure-property relationship of the derivatives is comprehensively studied in terms of their photophysical, electrochemical, structural, and electrical characteristics. IDID derivatives are either evaporated in vacuum or dissolved in common organic solvents to ensure applicalbility in different processing routes toward outstanding p-type semiconductor films. Among others, the excellently soluble compound 4H4TIDID (with 2- and 7-substituents of 5-hexyl-2,2'-bithiophene moiety, solubility >20 wt% in chloroform), shows the highest field-effect hole mobility of 0.97 cm(2)V(-1)s(-1) in a device constructed by vacuum-deposition and 0.18 cm(2)V(-1)s(-1) in device cosntructed by spin-coating, respectively. The 2D grazing incidence X-ray diffraction of 4H4TIDID films in both devices identically show the 2D molecular orientation favorable for the high transistor mobility.