n-Type selectivity and enhanced electron mobility in an ambipolar organic semiconductor induced by tetrathiafulvalene

Abstract

The realization of high-mobility unipolar organic semiconductors is pivotal for advancing next-generation optoelectronic technologies. The present work proposes a novel strategy for engineering charge transport in an ambipolar benzo[c]cinnoline-based semiconductor, (MOTPA)₂Ab, by achieving significantly enhanced n-type selectivity and electron mobility through complexation with tetrathiafulvalene (TTF). It is demonstrated that the formation of the (TTF)₂(MOTPA)₂Ab charge–transfer complex effectively reduces electron trap density below the SCLC detection limit via a mechanism of strategic hole passivation. While pristine (MOTPA)₂Ab exhibits an electron trap density of approximately 10¹⁶ cm⁻³, the (TTF)₂(MOTPA)₂Ab complex renders electron traps undetectable, thereby creating an effective near-trap-free transport channel. Consequently, the electron mobility is enhanced by 15-fold, increasing from 1.9 × 10⁻³ to 2.9 × 10⁻² cm² V⁻¹ s⁻¹. Simultaneously, hole transfer is meticulously suppressed, resulting in a precipitous decline in hole mobility from 7.2 × 10⁻⁵ to 1.7 × 10⁻⁷ cm² V⁻¹ s⁻¹. The results demonstrate that the (TTF)₂(MOTPA)₂Ab complex exhibits significantly enhanced n-type transport characteristics with strongly suppressed hole transport. It is evident that modulating hole dynamics via strong π-donors represents a promising strategy for optimizing trap suppression and achieving superior electron transport in organic semiconductors.