Naphthalene flanked diketopyrrolopyrrole: A new DPP family member and its comparative optoelectronic properties with thiophene- and furan- flanked DPP counterparts

Diketopyrrolopyrrole (DPP) has been one of the most promising building blocks for constructing organic semiconducting materials used in organic field-effect transistors (OFET). As we have known, extended π-conjugated structure can facilitate intermolecular orbital coupling which determines the magnitude of the charge transfer integral and thus the charge transport in devices. What is more, better intramolecular charge transport and intermolecular charge hopping depend on more superior morphology of the conjugated materials in thin film that is influenced by flexible substitutions. Based on the above principles, it is worthy designing and synthesizing fused ring flanked DPP monomers with alkyl chains to exploit their potential use in OFET. In this work, we first synthesized and characterized a new DPP derivative, naphthalene flanked DPP with butyl-octyl side chain (BO-DPPN). When comparing with its thiophene- and furan-flanked DPP analogues using the same common alkyl chain, BO-DPPN appears as most suitable for OFET applications. For example, DSC analysis demonstrates its high degree of crystallinity, UV–Vis spectra show a strong aggregation in solid state, XRD pattern indicates its tight and long-range ordered lamellar packing. As expected, the OFET devices function well when using BO-DPPN directly as active semiconductor and an impressive hole mobility of 0.0126 cm2 V−1 s−1 was observed with a bottom-contact/top-gate architecture using a solution processable approach indicating its promising potential for use in organic electronics.