Siloxane‐Functionalized Silicon Phthalocyanine OTFTs: High Hole Mobility and Unexpected <i>p</i> ‐Type Character

Abstract Phthalocyanines are widely used in organic electronics due to their excellent chemical stability and tunable electronic properties, but their synthesis and purification often present significant challenges due to their low solubility. An alternative synthesis for a siloxane‐substituted silicon phthalocyanine ( iso (Si 3 O) 2 SiPc) is reported and its integration as an active semiconducting material in organic thin‐film transistors (OTFTs) is demonstrated. This compound is easily synthesized and purified, exhibits high solubility, and achieves a hole mobility exceeding 1 cm 2 V −1 s −1 under ambient conditions—a record high mobility for silicon phthalocyanines (SiPcs). Moreover, SiPcs usually behave as n ‐type semiconductors, and iso (Si 3 O) 2 SiPc unexpectedly displays a unipolar p ‐type character. The semiconducting behavior is investigated through a combination of density functional theory (DFT) calculations and experimental characterization of thin‐film transistors. In particular, thin film characterization using GIWAXS reveals a high degree of crystallinity with an exceptionally uniform crystalline texture of iso (Si 3 O) 2 SiPc, supporting efficient charge transport and demonstrating the material's strong potential for high‐performance OTFT applications. These results highlight the importance of siloxane‐based functional groups as an effective strategy to develop high‐performance, conjugated small‐molecule‐based OTFTs.