High Performance Solution Processed n‐Type OTFTs through Surface Engineered F–F Interactions Using Asymmetric Silicon Phthalocyanines

Abstract

AbstractTwo novel asymmetric silicon phthalocyanine (SiPc) derivatives consisting of one axially substituted fluorine and one tri‐alkyl silane group are synthesized and characterized in n‐type solution processed bottom‐gate top‐contact organic thin‐film transistors (OTFTs). The effect of surface energy and fluorination are investigated at the dielectric/semiconductor interface by thin‐film X‐ray diffraction, atomic force microscopy, bright field real‐color microscopy, and grazing‐incidence wide‐angle X‐ray scattering to assess alterations in film conformation, microstructure, and morphology. Low surface energy dielectric modification and the presence of fluorine interactions produce films with large area crystalline domains that promote charge carrier transport resulting in high performing OTFTs, with a clear relationship determined between surface energy, fluorination, and OTFT operation. Through modifying deposition solvent and the exploitation of fluorine–fluorine interactions, the asymmetric SiPc derivative, (tri‐n‐hexylsilyl oxide) fluorosilicon phthalocyanine (F‐3HS‐SiPc), leads to high performing n‐type OTFTs with an average field‐effect mobility of 0.13 cm2 V−1 s−1 and a threshold voltage of 26.3 V. These results successfully demonstrate the use of asymmetric axial fluorination as a route to high performance n‐type OTFT devices through controlled self‐assembly by fluorine–fluorine interactions.