Organic field transistors attracted considerable attention due to their excellent compatibility with flexible and biological substrates, low cost, easy processing and chemical tunability of properties that enable their wide application in electronics, including: large area flexible displays, smart cards and sensors, biomedical devices and radio frequency identification tags among many more applications. Many high mobility organic semiconductors have been developed based on π-extended acenes, oligothiophene and their derivatives. A majority of organic semiconductors have relatively low band gaps, typically in the visible region of the spectrum (~2-3 eV). On the other hand, large band-gap semiconductors would be beneficial due to their intrinsically higher stability and illumination-independent transport. They could likely find applications in transparent field-effect transistors that are currently fabricated with oxide semiconductors and carbon nanotubes.
Researchers led by professor Dmitrii Perepichka at McGill University in collaboration with professor Hong Meng at Nanjing Tech University in China developed a novel organic semiconductor 2,6-bis(4-methoxyphenyl)naphthalene (BOPNA) with unprecedentedly large band gap of 3.35 eV and an apparent hole mobility measured in thin-film organic field-effect transistors in a saturation regime. Their work, now published in Advanced Electronic Materials, presents a detailed analysis of photo-physical, electrical, and structural properties of BOPNA, showing its high thermal stability, facile morphology reorganization upon annealing at low temperatures, and band-like transport established through the temperature-dependent mobility measurements..
The researchers reported a multi-gram scale high-yield synthesis of BOPNA by a simple Suzuki coupling of commercially available 2,6-dibromonaphthalene with 4-methoxyphenylboronic acid. Photo-physical studies revealed the optical band gap of 372 nm demonstrating complete optical transparency of the film in the visible region. An excellent photo-stability of current response of BOPNA was also observed in the output characteristics of the organic field transistors.
In totality, a novel naphthalene semiconductor BOPNA with a wide band gap of 3.35 eV, high thermal, high photo-stability and complete optical transparency has been synthesized herein. A distinctive characteristic of BOPNA-based transistors is their excellent photo-stability and independence of the electrical characteristics of the illumination conditions; this is important for a wide-range practical application of low-cost organic electronics. Quoting Dr. Perepichka, “it is now clear that a notion of the “semiconducting region” in organic semiconductors being limited by 3 eV band-gap is just a misconception and that it is possible to design efficient field-effect transistors with large band-gap organic materials”.
Lijia Yan, Filip Popescu, M. Rajeswara Rao, Hong Meng, and Dmitrii F. Perepichka. A Wide Band Gap Naphthalene Semiconductor for Thin-Film Transistors. Advanced Electronic Materials, volume 3 (2017) pages 1-8.Go To Advanced Electronic Materials