Transparent Triboelectric Nanogenerators and Self-Powered Pressure Sensors Based on Micropatterned Plastic Films

Abstract

Transparent, flexible and high efficient power sources are important components of organic electronic and optoelectronic devices. In this work, based on the principle of the previously demonstrated triboelectric generator, we demonstrate a new high-output, flexible and transparent nanogenerator by using transparent polymer materials. We have fabricated three types of regular and uniform polymer patterned arrays (line, cube, and pyramid) to improve the efficiency of the nanogenerator. The power generation of the pyramid-featured device far surpassed that exhibited by the unstructured films and gave an output voltage of up to 18 V at a current density of ∼0.13 μA/cm 2 . Furthermore, the as-prepared nanogenerator can be applied as a self-powered pressure sensor for sensing a water droplet (8 mg, ∼3.6 Pa in contact pressure) and a falling feather (20 mg, ∼0.4 Pa in contact pressure) with a low-end detection limit of ∼13 mPa. KEYWORDS: Nanogenerator, transparent, polymer, pressure sensor T he integration of flexible and transparent characteristics is an important component in the new organic electronic and optoelectronic devices 1−3 and has been achieved for various applications, including transistors, 4,5 lithium-ion batteries, 6 supercapacitors, 7,8 pressure sensors, and artificial skins. 9−12 Indeed, building flexible transparent energy conversion and storage units plays a key role in realizing fully flexible and transparent devices. In 2006, our group demonstrated the first piezoelectric ZnO nanogenerator that successfully converted mechanical energy into electric energy. 13 Since then, various nanogenerators (NGs) based on piezoelectric effect have been demonstrated. 14−17 As an important part in this field, some studies on fully integrated flexible and transparent NGs have been reported. 18−21 Almost all of them are based on piezoelectric ZnO nanowires and the entire device requires sophisticated design and a high degree of integration.The general physical process for energy conversion has three important steps: charge generation, charge separation, and charge flow. These steps were accomplished in piezoelectric NGs by employing the piezoelectric potential created under strain. Recently, we have developed a flexible triboelectric generator (TEG) using all-polymer based materials. 22 By stacking two thin polymer films made of Kapton and polyester (PET), a charge generation, separation, and induction process can be achieved through a mechanical deformation of the polymer films as a result of the triboelectric effect. This is a simple, low-cost, readily scalable fabrication process of generator that can convert random mechanical energy in our living environment into electric energy using the well-known triboelectric effect. Furthermore, through rational design, this new mode of power generation can be developed to build a high-output, flexible, and transparent NG.To make the device transparent and improve the power generation density, three approaches were employed in this research: (i) replacing Kapton ...

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