Rhodanine-Bridged Core-Expanded Naphthalene Diimide Derivatives for n-Type Semiconductors

Abstract

Abstract The core expansion of naphthalene diimides (NDIs) is an effective strategy to modulate frontier molecular orbital energy levels and improve device performances. Herein two new rhodanine-bridged and core-extended NDIs T1 and T2 were designed and synthesized. The rhodanine moiety could act not only as a π-spacer to enlarge the molecular conjugated system, but also as an electron-donating unit to tune the molecular energy levels. As a result, both T1 and T2 showed slightly lower lying LUMO energy levels (< − 4.2 eV) by ca. 0.1 eV and narrower optical band gaps (ca. 1.5 eV) by 0.5 eV compared to those of n-type organic semiconductor (OSC) NDI2DT-DTYM2.The solution-processed organic thin-film transistors based on T1 and T2 exhibited electron motilities in the range of 10−4–10−3 cm2 V−1 s−1, and the inverted perovskite solar cells constructed using T2 as electron transport materials provided a power conversion efficiency value of 8.82%. The results demonstrated that embedding rhodanine units in a NDI2DT-DTYM2 backbone is an effective approach to tune the energy levels and optical properties of OSCs, providing a new way to construct novel n-type OSCs with multifunctional optoelectronic applications.

Keywords

• rhodanine
• naphthalene diimides
• organic semiconductors
• organic thin-film transistors
• electron transport materials