Self‐powered e‐Skin based on integrated flexible organic photovoltaics and transparent touch sensors

There is a growing interest in the large area, lightweight, low-power electronic skin (e-Skin), consisting of a multitude of sensors over conformable surfaces. The use of multifunctional sensors is always challenging, especially when their energy requirements are considered. Herein, the heterogeneous integration of custom-made flexible organic photovoltaic (OPV) cells is demonstrated with a large area touch sensor array. The OPV can offer power density of more than 0.32 μW cm−2 at 1500 lux, which is sufficient to meet the instantaneous demand of the array of touch sensors. In addition to energy harvesting, it is shown that the OPVs can perform shadow sensing for proximity and gesture recognition, which are crucial features needed in the e-Skin, particularly for safe interaction in the industrial domain. Along with pressure sensing (sensitivity of up to 0.26 kPa−1 in the range of 1–10 kPa) and spatial information, the touch sensors made of indium tin oxide and monolayer graphene have shown >70% transparency, which allow light to pass through them to reach the bottom OPV layer. With better resource management and space utilization, the presented stacked integration of transparent touch-sensing layer and OPVs can evolve into a futuristic energy-autonomous e-Skin that can “see” and “feel.