Study of carrier transport in flexible organic field-effect transistors: Analysis of bending effect and microscopic observation using electric-field-induced optical second-harmonic generation

•Bending effect on flexible organic field effect transistors was studied.•The second-harmonic generation measurement was used to probe carrier motion.•Results showed that the grains affected carrier transport in flexible transistors.

We studied the effect of bending on the carrier transport properties of flexible 6,13-Bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) field-effect transistors. Results showed that the effective carrier mobility increased ~ 30% with a 1.5% mechanical strain (compressive stress), whereas it decreased ~ 15% with a − 1.5% strain (tensile stress). Theoretical analysis based on the Maxwell–Wagner model was carried out, and suggested that both carrier mobility and carrier density in the organic field-effect transistor (OFET) channel were modulated due to the mechanical strains. The microscopic electric-field-induced second harmonic generation (EFISHG) images showed that carrier transport was governed by the presence of grains of TIPS-pentacene. The EFISHG observation is a powerful tool to investigate carrier transport in flexible OFETs which are being subjected to mechanical strains.