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 transforming it into a high-performance unipolar n-type material through complexation with tetrathiafulvalene (TTF). It is demonstrated that the formation of the (TTF)2(MOTPA)2Ab charge-transfer complex effectively eliminates electron trap states via a mechanism of strategic hole passivation. While the 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 trap-free transport channel. Consequently, 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 obtained clearly demonstrate that the (TTF)2(MOTPA)2Ab complex is a unipolar n-type semiconductor. It is evident that modulating hole dynamics via strong π-donors represents a universal pathway to optimize trap suppression and achieve superior electron transport in organic semiconductors.