Structural isomeric effect on spin transport in molecular semiconductors.

Molecular semiconductor (MSC) is promising candidate for spintronic applications benefited from its long spin lifetime caused by light elemental-composition essence and thus weak spin-orbit coupling (SOC). According to current knowledge, the SOC effect, normally dominated by the elemental composition, is the main spin-relaxation causation in MSCs, and thus molecular structure induced change of SOC is one of the most concerned issues. In theoretical study, molecular isomerism, a most prototype phenomena, has long been considered to possess little difference on spin transport previously, since elemental compositions of isomers are totally same. However, here in this study, quite different spin-transport performances have been demonstrated in ITIC and its structural isomers BDTIC experimentally, for the first time, though the charge transport and molecular stacking of two films are very similar. Together with further experiments of electron-paramagnetic resonance and density-functional-theory calculations, we reveal that noncovalent-conformational locks formed in BDTIC can lead to enhancement of SOC and thus decrease the spin lifetime. Hence, this study suggests the influences from structural-isomeric effect must be taken into account for developing high-efficient spin-transport MSCs, which also provides a reliably theoretical basis on solving the great challenge of quantificational measurement of NCLs in films in the future. This article is protected by copyright. All rights reserved.