Vacuum Pressure Leads to an Organic Molecular Electronic Response

N, N'-Bis(n-octyl)-1,6-dicyanoperylene-3,4: 9,10-bis(dicarboximide) (PDI8-CN2) organic thin film transistors (OTFTs) were found to exhibit a remarkable change of electrical conductivity when characterized under vacuum pressure in the range from 70 Pa (low vacuum) to 100 kPa (atmosphere). A similar phenomenon was also observed on pentacene-based OTFTs but not on two-dimensional layered MoS2 TFTs. The mechanism to interpret a vacuum pressure response of organic thin film transistors is assumed to be the miniscule change of intermolecular distances under applied pressures. The values of variation of intermolecular distances are theoretically calculated based on a hopping model of the Marcus transfer rate. In addition, the Young's modulus of the PDI8-CN2 thin film evaluated through this model agrees well with the experimental values measured by atomic force microscopy ( AFM) characterization using a Peakforce Quantitative NanoMechanics (QNM) mode.