Piezo-Phototronic In2Se3 Nanosheets as a Material Platform for Printable Electronics toward Multifunctional Sensing Applications

Abstract

A facile, ultralow-cost, and up-scalable printable manufacturing process of flexible, multifunctional sensors that respond to more than one external stimulus could have a pivotal role in low-cost wearables and portable systems for Industry 4.0. Herein, using a low capex, in-house spray coating system, the fabrication of a low-cost photodetector that is tuneable by mechanical strain exploiting the piezo-phototronic nature of defect-free 2D In2Se3 nanosheets is reported. Moreover, force sensors that respond to different levels of applied force are spray-coated by using In2Se3 nanosheets. Regarding the photodetector, a nonmonotonic and asymmetric effect of strain on photocurrent response is shown exhibiting a local maximum at the 23°–32° compressive angle range and a slight hysteresis. Forward compressive bending leads to a photocurrent enhancement by 27% at 32° and reverse by 31% at 23°, while tensile strain leads to a current suppression by 8–10% at 23°–32° angle. The resulting force sensor repeatably demonstrates discrete piezoelectric voltages in the millivolt scale upon different mass loads, opening the path for force and tactile sensing applications. Applying industrially compatible materials for the underlying flexible substrate and electrodes, combined with spray coating, removes manufacturing complexities that engage costly and energy intensive fabrication.