Molecular semiconductors and the Ioffe-Regel criterion: A terahertz study on band transport in DBTTT

Terahertz electromodulation spectroscopy provides insight into the physics of charge carrier transport in molecular semiconductors. The work focuses on thin-film devices of dibenzothiopheno[6,5-b:6',5'-f]thieno[3,2-b]thiophene. Frequency-resolved data show a Drude-like response of the hole gas in the accumulation region. The temperature dependence of the mobilities follows a T-1/2 power law. This indicates that the thermal mean free path of the charge carriers is restricted by disorder. Only a fraction of approximately 5% of the injected carriers fulfills the Ioffe-Regel criterion and participates in band transport. (C) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http:// creativecommons.org/licenses/by/4.0/).