Microstructure of Oligofluorene Asymmetric Derivatives in Organic Thin Film Transistors

Abstract

In organic thin film transistors (OTFT), modifying the molecular chemical structure affects the molecular packing and thin film morphology, which both sensitively influence the charge carrier mobility. A detailed understanding of the interplay of molecular chemical structure, molecular packing, and thin film morphology is therefore necessary to improve OTFT performance. Fluorene-bithiophene-fluorene (FTTF) derivatives have demonstrated great potential for use as the active layer for OTFTs. A series of FTTF asymmetrically substituted derivatives were synthesized to fine-tune the film properties. In this study, the thin film microstructure details of FTTF and several FTTF derivatives with asymmetrically substituted alkyl-chains of different lengths are studied and compared with their electrical performance in thin film transistor devices. The respective unit cells were characterized using grazing incidence X-ray diffraction (GIXD), and for FTTF the detailed molecular packing was determined from the GIXD int...