Tensile properties of two-dimensional poly(3-hexyl thiophene) thin films as a function of thickness

Abstract

Ultra-thin conjugated polymer films are promising candidates for flexible electronics, but the effect of the film thickness on the tensile properties of 2D conjugated polymer films at the several-nanometer scale has not been investigated. In this paper, ultra-thin poly(3-hexylthiophene) (P3HT) films (2.07 ± 0.36 nm, 4.03 ± 0.25 nm, 6.53 ± 0.45 nm) were prepared by a lamination method, and OFET devices with ultra-thin P3HT films with different thicknesses and degrees of stretching as active layers were fabricated by the film on elastomers (FOE) method. The relationship between the thickness of the ultra-thin P3HT films and their tensile properties was investigated by optical microscopy (OM), atomic force microscopy (AFM), and UV-visible spectroscopy. The results showed that the laminated ultra-thin P3HT films (<10 nm) exhibited better tensile properties than the directly spin-coated P3HT thick films (43 ± 1.5 nm) regardless of the number of layers. The ultra-thin P3HT films showed improved tensile resistance as the thickness decreased, and the 1 layer (2.07 ± 0.36 nm) film showed the best tensile properties. The average mobility of the devices parallel to the stretching direction at 100% tensile strain was 6.06 × 10⁻⁴ cm² V⁻¹ s⁻¹, with only minor cracks at 100% tensile strain and a 25% retention in mobility compared with the initial state.