Improving Carrier Mobility of Near-Amorphous Donor-Acceptor Conjugated Polymer Thin Films via Promoting Intensive and Continuous Polymer Aggregations

For near-amorphous donor-acceptor (D-A)polymers,local aggregates can serve as charge transport contacts between conjugatedbackbones, which are important for achieving high carrier mobilityof polymer films as optoelectronic materials. However, regulatingthe aggregation density and continuity of near-amorphous conjugatedpolymers remains significantly challenging because of complex interactionsbetween polymers and processing solvents. To address this issue, wepropose a strategy to effectively promote the continuous aggregationsof poly(indacenodithiophene-co-benzothiadiazole)(IDTBT) by providing more space for polymer chain movement. Specifically,an optimized amount of chlorohexadecane was added into an IDTBT chlorobenzene(CB) solution, and the subsequent spin-coated polymer film was furtherannealed at 150 & DEG;C for 30 min. Chlorohexadecane can act as aspacer molecule that significantly increases the distance betweenIDTBT chains due to its strong interaction with both the polymer backboneand side chain. During annealing, the chlorohexadecane additive volatilizesand leaves large space, which further promotes the self-assembly ofIDTBT polymer chains into a coarse fiber-like network through effective & pi;-& pi; interactions. The IDTBT films obtained usingthis strategy show much more apparent backbone aggregates in bothsize and continuity than those in both pristine (without additives)and nonannealed (with additives) films. Furthermore, physicochemicalfeatures in these films were verified by the characterization of ultraviolet-visible(UV-vis) spectra, grazing-incidence wide-angle X-ray scattering(GIWAXS), atomic force microscopy (AFM), and molecular dynamics simulations.The average carrier mobility (& mu; (ave)) of 1% chlorohexadecane-treated IDTBT films after annealing reaches3.61 & PLUSMN; 0.09 cm(2) V-1 s(-1), 2-fold higher than that of annealed CB films.