Naphthodipyrrolopyrrole-based Aza-BODIPY dye for N-type organic field-effect transistors

To date, n-type semiconductor designs are less investigated than their p-type counterparts, due to the fact that the charge transport mobility and the stability of the n-type materials are generally lower than those of the p-type ones. Well-defined n-type semiconductors often require low lowest unoccupied molecular orbital (LUMO) levels that facilitate the electron injection from the electrode into the semiconductors. Therefore, it is of significance to explore novel chromophores with strong electron-deficient properties, yet it is still challenging. Herein, a naphthodipyrrolopyrrole-based dimeric aza-boron dipyrromethene (Aza-BODIPY) dye (NDP-AB) is designed and synthesized. The optical studies indicate that NDP-AB presents a blue spectral shift (111 nm) in solution phase compared to the thin film state, while exhibiting a photoluminescence emission quenching. The NDP-AB semiconductor demonstrates strong acceptor properties with a low LUMO energy level of only −4.25 eV, owing to the multi-fluorine atoms, unsaturated nitrogen atoms, as well as the amide functional groups. Moreover, the large conjugation system, highly planar core, along with the large transition dipole on the line that links 2-position with 6-position of the BODIPY core, result in NDP-AB with a strong H-aggregation. As a consequence, the NDP-AB-based semiconductors show a good n-type behavior with an average electron mobility of 0.16 cm² V⁻¹ s⁻¹. Our work, proposes a strong electron-deficient chromophore that is a promising candidate as building block of organic field-effect transistors. Our design strategy paves the way for the identification of more n-type semiconductor materials with high-performance.