Flexible, transparent and high-power triboelectric generator with asymmetric graphene/ITO electrodes

Abstract

The reported flexible and transparent triboelectric generator (FTTG) can only output ultralow power density (∼2 μW cm −2 ), which has seriously hindered its further development and application. The low power density of FTTG is mainly limited by the transparent material and the electrode structure. Herein, for the first time, a FTTG with a superior power density of 60.7 μW cm −2 has been fabricated by designing asymmetric electrodes where graphene and indium tin oxide (ITO) act as top and bottom electrodes respectively. Moreover, the performance of FTTG with graphene/ITO (G/I) asymmetric electrodes (GI-FTTG) almost remains unchanged even after 700 cycles, indicating excellent mechanical stability. The excellent performance of GI-FTTG can be attributed to the suitable materials and unique asymmetric electrode structure: the extraordinary flexibility of the graphene top electrode ensures the GI-FTTG excellent mechanical robustness and stability even after longer cycles, and the bottom electrode with very low sheet resistance guarantees lower internal resistance and higher production rate of induction charges to obtain higher output power density. It shows that lightemitting diodes (LED) can be easily powered by GI-FTTG, which demonstrates that the GI-FTTG is very promising for harvesting electrical energy from human activities by using flexible and transparent devices.

Direct Visualization of Cross-Sectional Strain Distribution in Flexible Devices

“…It is most important to minimize the strain of functional inorganic materials, which are brittle and fragile, such as electrodes including indium-tin-oxide, graphene, and alumina encapsulated by various thin-film layers, to prevent premature failures under bending. − An effective mechanical approach to reduce the imposed strain on such components is to place the brittle functional layers close with the mechanical neutral plane (NP) where the strain is free under bending. This NP strategy has been widely used to enhance the bending reliability of flexible devices. − As a promising expansion of the NP strategy, a novel laminated structure has recently been proposed, which generates multiple NPs (MNPs) in a device by adopting very soft interlayers.…”

Piezoelectricity and Biocompatibility of Flexible ScxAl(1–x)N Thin Films for Compliant MEMS Transducers

“…The asymmetric nature of the positive and negative voltage peaks can be attributed to a slightly different stress applied to the device during compression/release states provided by the linear motor-based measurement setup . The asymmetry of the positive and negative current peaks has been ascribed to different charge relaxation times in the piezoelectric device . Doping of Sc into AlN would affect the mechanical properties of the piezoelectric layer.…”

“…25 The asymmetry of the positive and negative current peaks has been ascribed to different charge relaxation times in the piezoelectric device. 26 Doping of Sc into AlN would affect the mechanical properties of the piezoelectric layer. This has consequences in the reliability and stability of the microdevices for long-term applications.…”

Recent progress in flexible tactile sensor systems: from design to application

“…However, considering the unique energy collection characteristics of the piezoelectric materials, they have very important advantages in the development of fast dynamic response, low energy consumption, and selfpowered flexible tactile sensors. The piezoelectric materials commonly used in piezoelectric sensors include lead zirconate titanate (PZT) [52][53][54][55][56] , ZnO [57] , BaTiO 3 [58] , LiTaO 3 [59,60] , Group III-nitride (III-N) materials (AlN and GaN) [61][62][63] , and intrinsic flexible polyvinylidene fluoride (PVDF) [64][65][66] .…”