Solution-processed polycrystalline copper tetrabenzoporphyrin thin-film transistors

The demonstration of organic thin-film field-effect transistors (OFETs) using a solution-processable form of the organometallic molecule copper tetrabenzoporphyrin (CuTBP) is reported. A soluble precursor was spun-cast into an amorphous, insulating thin-film, and thermally annealed at 165 °C for 30 min into a polycrystalline organic semiconductor. Absorbance spectroscopy displayed characteristics of porphyrin macrocycles. Microscopy reveals the formation of domains comprising aligned nanorod aggregates with dimensions of 55 nm wide, 300 nm long, and 100 nm tall on the gate insulator surface. OFETs demonstrated field-effect mobilities typically on the order of 0.1 cm2/V s, threshold voltages around 5 V, subthreshold slopes around 4 V/dec, and ON-/OFF-current ratios near 104.