Effect Of Silicon Nanostructure Morphology On Hydrovoltaic Device And Its Integration With Triboelectric Nanogenerator

Hydrovoltaic technology,which harvests electricity from water,has attracted wide attention because of its low cost,stable performance,and no mechanical energy required.Particularly,in recent years,the output of hydro voltaic device has been boosted by a silicon nanowire arrays(SiNWs)based structure,which relies on water evaporation.Besides,triboelectric nanogenerator(TENG)is proposed to convert the mechanical energy of waterdrop into electricity by utilizing dielectric material as a functional layer.However,the output of SiNWs based hydrovoltaic device is limited by the length of SiNWs.Even worse,either hydro voltaic device or TENG can only exploit one form of energy contained in water,which severely hinders the device application.Here,we have investigated the influencing factors for hydrovoltaic device such as morphology,structure,and length of SiNWs.In addition,hydrovoltaic device is integrated with TENG to convert thermal energy during evaporation and mechanical energy of waterdrop into electricity simultaneously,which broadens the possibilities for applications.The main investigation of this topic is shown as followed:1.The tilted SiNWs were fabricated by metal-assisted chemical etching.SiNWs of various crystal orientations have been obtained on silicon of different crystallographic orientations.Characterized by scanning electron microscopy,tilted SiNWs exhibit a length of 45 μm on Si(110)wafer.After adjusting the concentration of AgNO3 and H2O2 during the etching,tilted SiNWs can deliver an optimal morphology,which is crucial to the output of hydrovoltaic device.2.The influence factors of hydrovoltaic device based on tilted SiNWs are fully explored by comparing the output of hydrovoltaic device based on various lengths and doping concentration of SiNWs.The hydrovoltaic device can generate an open-circuit voltage(Voc)of 500 mV and a short-circuit current density(Jsc)of 9.5 μA/cm2,along with a maximum power density of 0.9 μW/cm2 by utilizing the heavily doped tilted SiNWs with a length of 45 μm.Moreover,due to the intrinsic structure of the tilted SiNWs,the hydrovoltaic device shows a superior ability for water retention,contributing to a preferable output under the ambient environment,which makes it more likely for the potential application of siliconbased hydrovoltaic devices in the future.3.An integrated device is built to couple the hydrovoltaic technology with triboelectric effects by using a mutual electrode and realize the simultaneous harvesting of energy from water in different methods.The contributory factors of TENG such as the material of the friction layer,the morphology of the friction layer,the material of the top electrode,and releasing height along with the volume of droplets were explored.TENG delivers a boosted output with a peak Voc of 200 V along with a peak short circuit of 60 μA.The corresponding power density of TENG is 2.5 W/m2 by a single droplet in the ambient environment.Meanwhile,the SiNW-based HD with hierarchical nanofabric carbon electrode can constantly generate a Voc of 550 mV and an Jsc of 30 μA/cm2,with an output of 80 mW/m2.The integrated device can convert both mechanical energy and thermal energy into electricity,which provides a new idea for collecting energy from natural rainwater.