Available on-demand - F.EN01.06.05
Strategy to Choose Best Building Blocks for Efficient Triboelectric Generator Devices
Linards Lapčinskis1,Kaspars Malnieks1,Artis Linarts1,Māris Knite1,Andris Sutka1
Riga Technical University1
TEG devices have potential to satisfy growing energy needs in portable electronics and sensors providing a clean alternative to conventional batteries.1 TEG devices are produced from cheap, lightweight, flexible, widely used polymer materials and offer promise to capture neglected and unutilized forms of mechanical energy. TEG device consists from two conductive electrodes from which at least one is covered with polymer insulator film.1 The two electrodes in TEG are connected by outer circuit and upon electrode oscillation surface charge on polymer layers and electric potential is created that drive electrons to flow between two electrodes in order to balance this electric potential difference. TEG devices can be operated in different modes – vertical separation, sliding, rotating, single electrode etc.2 but the key feature for high TEG efficiency is surface charge from contact electrification.3
Different mechanisms are responsible for contact electrification and depend on material used. It is well demonstrated, that on metal-metal, metal-semiconductor or semiconductor-semiconductor contact the electron transfer occurs,4,5 but this is not so obvious for polymer insulators.6 The three mechanisms for polymer insulator contact electrification are considered – electron transfer,7 ionic transfer,6 and covalent bond cleavage.8 Electron transfer between polymers is doubtful, because there are no available free electrons in insulators. Usage of the term “effective work function” in connection to the driving force for charge exchange between polymer insulators is also questionable even if the polymer is contacted with metal.6 Ion exchange between contacted polymer insulators has been considered, because water under ambient conditions is adsorbed even on hydrophobic polymers.9 The water layers on contacted surfaces fuse together upon contacting and as different polymer materials may have different affinity towards cations and anions in water, the imbalance between ions form during separation, thus creating surface charge.6 However, it has been proven, that contact electrification of polymer insulators also occurs in complete absence of water.10
In our work we show that polymer contact-electrification can be predicted using their cohesive energy density. This allows us to select the most suitable materials as the building blocks for efficient TEG devices.
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