• Takeya, Jun
• Ariga, Katsuhiko

Abstract

<jats:title>Abstract</jats:title><jats:p>The chemical doping of molecular semiconductors is based on electron transfer reactions between the semiconductor and dopant molecules; here, the molecular orbital energy of the dopant is key to control the Fermi level of the semiconductor. The tunability and reproducibility of chemical doping are limited by the availability of suitable dopant materials and effects of impurities such as water. In this study, we focused on proton-coupled electron transfer (PCET) reactions, which are widely employed in biochemical processes; changes in the free energy in these redox reactions depend on not only the molecular orbital energy but also an easily handled parameter, that is, proton activity. We immersed p-type organic semiconductor (OSC) thin films in aqueous pH-controlled doping solutions under ambient conditions. In accordance with the Nernst equation, the Fermi levels of the semiconductors were controlled with a high degree of precision, ca. thermal energy of 25 meV at RT, over a few hundred meV around the band edge. The OSC thin films showed repetitive and reproducible resistance changes as a function of the pH of the doping solution, which could lead to the development of a reference-electrode-free, resistive pH sensor. Knowledge of the connection between semiconductor doping and proton activity, a widely employed parameter in chemical and biochemical processes, may help create a new platform for developing ambient semiconductor processes and biomolecular electronics.</jats:p>

Topics

• impedance spectroscopy
• thin film
• semiconductor