Strong Magnetic Field Annealing for Improved Phthalocyanine Organic Thin‐Film Transistors

Abstract Thin‐film microstructure, morphology, and polymorphism can be controlled and optimized to improve the performance of carbon‐based electronics. Thermal or solvent vapor annealing are common post‐deposition processing techniques; however, it can be difficult to control or destructive to the active layer or substrates. Here, the use of a static, strong magnetic field (SMF) as a non‐destructive process for the improvement of phthalocyanine (Pc) thin‐film microstructure, increasing organic thin‐film transistor (OTFTs) mobility by twofold, is demonstrated. Grazing incident wide‐angle X‐ray scattering (GIWAXS), X‐ray diffraction (XRD), and atomic force microscopy (AFM) elucidate the effect of SMF on both para‐ and diamagnetic Pc thin‐films when subjected to a magnetic field. A SMF is found to increase the concentration of oxygen‐induced radical species within the Pc thin‐film, lending a paramagnetic character to ordinarily diamagnetic metal‐free Pc and resulting in magnetic field induced changes to its thin‐film microstructures. In a nitrogen environment, without competing degradation effects of molecular oxygen, SMF processing is found to favorably improve charge transport characteristics and increase OTFT mobility. Thus, post‐deposition thin‐film annealing with a magnetic field is presented as an alternative and promising technique for future thin‐film engineering applications.