Introduction of Metal Coordination Bonds into Conjugated Polymers to Increase Carrier Mobility and Stretchability

Conjugated semiconducting polymers are the core materials of flexible and stretchable electronics. However, some polymer semiconducting films with high carrier mobility are brittle, and the carrier mobility decreases rapidly as the tensile strain increases. Herein, the metal coordination bonds are introduced into the conjugated polymers to enhance coplanarity of the backbone to increase the charge transport mobility, and the strain energy is dissipated through the breakage of metal coordination bonds and π–π aggregates when strain is applied. This idea is proved by soaking indacenodithiophene-co-benzothiadiazole (IDTBT) thin film in ethanol solution with varying concentrations of zinc chloride (ZnCl2). Zn2+ ions can coordinate with the nitrogen atom on the BT unit, as verified by XPS, FT-IR, and density functional theory calculations. The results of Raman, UV–vis, and molecular dynamics simulations indicate that the treated films exhibit improved backbone coplanarity and polymer aggregation, resulting in a 2-fold enhancement in carrier mobility. Furthermore, during stretching, the carrier mobility of ZnCl2-treated IDTBT films decreases from 2.21 ± 0.15 to 1.43 ± 0.14 cm2 V–1 s–1, which is much slower than the decrease observed in the pristine films (decreases from 1.4 ± 0.15 to 0.18 ± 0.01 cm2 V–1 s–1) at 100% strain.