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.