Fluorinated Benzothiadiazole-based polymers with chalcogenophenes for organic field-effect transistors

Abstract

The effect of incorporating chalcogenophene comonomers, namely, furan, thiophene, and selenophene, on the optoelectrical properties of cyclopentadithiophene-based polymers (P1, P2, and P3, respectively) for organic field-effect transistors is reported. The optical, electrical, and morphological properties of the P1, P2, and P3 are investigated. Compared to the other polymers, the P2 showed the highest crystallinity with the shortest π–π stacking distance ( d π–π ≈ 3.58 Å) and the longest crystalline length ( L c ≈ 40 Å), as confirmed by two-dimensional grazing incidence wide-angle X-ray diffraction. However, P3 had the highest hole mobility ( μ = 0.25 cm 2 /V-s), which is higher than P1 ( μ = 0.06 cm 2 /V-s) and P2 ( μ = 0.20 cm 2 /V-s). The relatively lower mobility of the P2 than of the P3 is attributed to its island-like crystalline domains, confirmed by atomic force microscopy results and the edge-on dominant orientation. Our findings suggest a new design guideline for developing high-mobility π-conjugated polymers. • We first address the importance of size of substituted atoms in determining optoelectronic properties and thin film crystallinity of the FBT-based polymers. • The influence of chalcogenophene atom substitution on optoelectrical properties of the FBT-based polymers was thorough investigated. • Combining a highly-crystallized molecular packing with effective morphologies led to the best hole mobilities of 0.25 cm 2 V −1 s −1 for P3.