A high-performance organic field-effect transistor based on platinum(II) porphyrin: Peripheral substituents on porphyrin ligand significantly affect film structure and charge mobility

Organic field-effect transistors incorporating planar π-conjugated metal-free macrocycles and their metal derivatives are fabricated by vacuum deposition. The crystal structures of [H₂(OX)] (H₂OX= etioporphyrin-I), [Cu(OX)], [Pt(OX)], and [Pt(TBP)] (H₂TBP=tetra-(n- butyl)porphyrin) as determined by single crystal X-ray diffraction (XRD), reveal the absence of occluded solvent molecules. The field-effect transistors (FETs) made from thin films of all these metal-free macrocycles and their metal derivatives show a p-type semiconductor behavior with a charge mobility (μ) ranging from 10^-6 to 10^-1 cm²V^-1 s^-1. Annealing the as-deposited Pt(OX) film leads to the formation of a polycrystalline film that exhibits excellent overall charge transport properties with a charge mobility of up to 3.2×10^-1 cm ²V^-1 s^-1, which is the best value reported for a metalloporphyrin. Compared with their metal derivatives, the field-effect transistors made from thin films of metal-free macrocycles (except tetra-(n-propyl)porphycene) have significantly lower μ values (3.0×10^-6-3.7×10^-5 cm²V ^-1 s^-1).