Role of the Alkylation Patterning in the Performance of OTFTs: The Case of Thiophene-Functionalized Triindoles

Abstract

Organic semiconductors have emerged as potential alternatives to conventional inorganic materials due to their numerous assets and applications. In this context, the star-shaped triindole core stands as a promising system to design new organic materials with enticing charge-transporting properties. Herein, we present the synthesis of three thiophene-containing triindole derivatives that feature N-alkyl chains of different lengths, from methyl to decyl. The impact of the alkylation patterning on the crystallinity of the thin films and their resultant performance as semiconductor have been analyzed. All derivatives displayed p-type semiconductor properties, as demonstrated via both TOF measurements and integration in organic thin-film transistor (OTFT) devices. The attachment of longer alkyl chains and the functionalization of the silicon substrate with octadecyltrichlorosilane (OTS) prompted better OTFT characteristics, with a hole mobility value up to 5 × 10−4 cm2 V−1 s−1. As elucidated from the single crystal, this core is arranged in a convenient cofacial packing that maximizes the π-overlapping. The analysis of the thin films also corroborates that derivatives possessing longer N-alkyl chains confer a higher degree of order and a more adequate morphology.