A FRET-Enabled Ordered Nematic Liquid Crystal en Route to Electrically Conductive Solution-Processable Nanofilms

With the rising demand for large-area solution-processable organic semiconductors, the high structural order of any charge-transport system needs to be supplemented with simultaneous flexibility to form uniform films in devices, especially to effectuate charge carrier extraction at its electrode interfaces. Hence, approaching nematic mesophases to induce fluidic properties in an organic charge-transport layer, without hindering its electrical conduction properties, assumes the utmost importance. In this context, we design a luminescent discotic liquid crystal (DLC) dyad molecularly engineered to tune its self-assembly to facilitate a columnar nematic (N_Col) phase at room temperature, balancing the dichotomy of ordered columnar superstructures with the dynamicity of a nematic phase. Rationally collated photophysical, theoretical, and electrochemical studies demonstrate that the constituent donor and acceptor units govern electronic interactions and energy transfer in the excited state, predominantly influenced by low reorganization energies. With this uniquely ordered nematic phase rendering defect-free solution-processable nanofilms, the DLC was suited to fabrication of highly stable nanoscale devices under ambient conditions. Exhibiting a remarkable charge-extraction property in its undoped native state with an electrical conductivity of 10^–4 S m^–1, this report of a N_Col DLC nanofilm in solution-processable vertical-transport devices is a pioneering contribution to the knowledge of self-assembly and charge conduction of ordered nematic phases in DLCs.