Carbon Nanotube Mesh/Silicon Nanowire Array S Based Hydrovoltaic Devices And Their Charge Transport Modulation

In recent years,hydrovoltaic technology,which uses water as a source of energy,has become an energy conversion method with significant development potential due to its wide range of energy sources and the clean energy of its non-polluting products.The efforts of researchers have led to the development of hydrovoltaic technology material systems such as carbon materials,polymer materials and inorganic semiconductor materials.Silicon nanowire arrays(SiNWs)are excellent hydrovoltaic materials due to the low price,low internal resistance,high carrier transport properties and abundant nanopores.However,its output still can’t meet the energy supply requirements of commercial electronic products.Developments of hydrovoltaic technology are mainly limited to the selection of electrodes for the devices,the adaptation to the environment and the modulation of the charge transport.The research focuses on the electrode materials of hydrovoltaic devices,moisture absorption strategy and charge selective transport layers on the performance enhancement and working mechanism of hydrovoltaic devices.The main studies are as follows:1.A hydrovoltaic device based on carbon nanotube(CNT)mesh electrodes was proposed and realized.By the characterization of scanning electron microscopy and electrical conductivity,the porous CNT films allowed water molecules to rip through the conductive films quickly on the one hand,and provided a high conductivity to collect the electrons generated by the device in time on the other hand.When the size and hydrophilicity of CNT were optimized,the nanostructure of carbon nanotubes enabled capillary penetration of water molecules and provided a large number of channels for ion transport.Fourier infrared spectroscopy(FTIR)and Raman spectroscopy were used to investigate the mechanism of device performance after oxygen plasma treatment of CNT.The hydrophilicity of CNT after oxygen plasma treatment was enhanced to become excellent ion transport channels,increasing the strong coupling with water molecules and substantially improving the charge transport and charge collection efficiency by the introduction of oxygen functional groups.Finally,a CNT/carbon paste composite electrode was designed to further increase the specific surface area in the electrode,which was expected to reduce the evaporation enthalpy of water in the electrode and can maintain high efficiency of evaporation of water molecules.The device performance was significantly improved by using CNT as the electrode material for SiNWs based hydrovoltaic devices,with an open-circuit voltage of 753 mV and a current density of 60 μA/cm2.2.A CNT electrode/biomass material/SiNWs moisture electricity generation device(MEG)with a moisture absorption layer(silk protein and hyaluronic acid)has been designed and realized with an order of magnitude improvement in device performance.The device can maintain a stable DC high current and voltage output at medium humidity(60%)with an open circuit voltage of 500 mV and a short circuit current of 0.8 μA/cm2.We characterized the hygroscopic ability of silk protein and hyaluronic acid,which showed significant moisture harvesting effect and also exhibited water retention property,and the hygroscopic layer of biomass materials enabled the device to maintain stable output at low and fluctuating ambient humidity.3.CNT film/polyelectrolyte/SiNWs MEG with charge-selective layer structure was designed and realized.In this structure,polydiallyldimethylammonium chloride(PDDA)was selected as the charge-selective layer and spontaneous hygroscopic layer,the PDDA based SiNWs-MEG can generate a stable open-circuit voltage of 1000 mV,and DC current of 8.2 μA/cm2,and the output power can reach 2.2 μW/cm2 under a natural environment of 60%humidity and 25℃.The ion transport behavior across membranes of poly electrolytes with different electrical properties has been studied by Kelvin probe microscopy.The energy source of moisture electricity generation is most likely thermal energy from the Gibbs free energy change of water molecules.The display device light-emitting diode(LED)arrays were powered by the series integration of the devices.