Highly-stable, green-solvent-processable organic thin-film transistors: angular- vs. linear-shaped carbazoledioxazine derivatives

The design and synthesis of new dye/pigment-based semiconductors have made a significant contribution to the development of organic electronics. However, there are few detailed studies on the comparison of isomeric dye/pigment molecules, which play an important role in revealing the molecular structure-property-device performance relationships. In this study, we, for the first time, compared the thermal stability, optical, electrochemical, molecular assembling and charge transport properties of isomeric angular and linear-shaped carbazoledioxazine derivatives, namely Ang-CZ and Lin-CZ, respectively. While the molecular shapes hardly affect the optical bandgaps and energy levels, they dramatically alter the charge transport characteristics. Accordingly, Lin-CZ exhibited a two orders of magnitude higher mobility than Ang-CZ, evaluated by thin-film transistors (TFTs). Further studies suggested that Lin-CZ tends to adopt a denser molecular packing motif and a higher molecular orbital overlapping than Ang-CZ which is revealed by grazing-incidence wide-angle X-ray scattering (GIWAXS), atomic force microscopy (AFM), and density functional theory calculations (DFT). More importantly, Lin-CZ-T, a p-extended derivative of Lin-CZ, showed a relatively high and stable TFT mobility of over 0.1 cm(2) V-1 s(-1), which was revealed by using an environmentally-benign solvent and a pre-aggregation method. Our findings will provide direction for developing more promising molecular semiconductors and organic TFT technology.