Fine-tuning the molecular energy levels by incorporating thiophene units onto the π-backbone of core-expanded naphthalene diimides

A series of core-expanded naphthalene diimides (NDI-DTYM) and thiophene-based derivatives (1a–c) were designed and synthesized to investigate the relationship between molecular structures and the highest occupied molecular orbital (HOMO) energy levels but has little impact on the lowest unoccupied molecular orbital (LUMO) energy levels. The results demonstrated that increasing the number of thiophene units can gradually elevate the HOMO energy levels but had little impact on the LUMO energy levels. The n-channel organic field-effect transistors (OFETs) based on 1b and 1c have demonstrated that these almost unchanged LUMO energy levels are proper to transport electrons.

Graphical abstractA series of organic semiconductors based on NDI-DTYM and thiophene were designed to investigate the relationship between molecular structure and the molecular frontier orbital energy levels. The results demonstrated that increasing the number of thiophene units leads to the gradually elevated HOMO energy levels but the almost unchanged LUMO levels.Figure optionsDownload full-size imageDownload as PowerPoint slide