Study On The Contact-separation Mode Triboelectric Nanogenerators Based On Contact Interface Effect

With the realization of the Internet of Things(Io T),electronic devices tend to be more and more miniaturized,portable and multifunctional.As the basic unit of electronic equipment,sensors are responsible for the detection of complex environments and the collection of real-time information.However,conventional power modules can no longer meet the growing demand.Therefore,micro and nano energy systems based on nanogenerators are developed to collect various energy in the working environment and convert them into electric energy,which ensuring the continuous and stable operation of electronic devices.Compared with other NGs,TENGs have many advantages such as simple preparation process,low material cost,high output power and conversion efficiency.In this paper,materials have been classified into three categories according to their electrical properties: metal,polymer and semiconductor.The output characteristics and operating mechanism of polymerpolymer/metal contact have been extensively studied,so we will not discuss them too much in this thesis.Other than that,four types of TENGs formed by their two-by-two combinations were discussed.1.Thirteen metal films,including Ag,Al,Zn and Pb were used,among which Ag was adopted as a fixed negative tribo-material due to its high work function and more stable property than most metals.Metal-Ag TENGs were prepared for subsequent testing.Metals have no-modulation of energy band due to its high electron concentration,thus only two current peaks induced by the CE effect exist same as polymer-polymer TENGs or polymer-metal TENGs.The output performance and charges transferred were determined by the work function difference between the two tribo-metals.Compared with other TENGs,the output resistance of metal-metal TENGs is generally small,allowing the output power to be easily coupled to external circuit,which plays a guiding role in expanding the practical application scenarios of TENGs.2.Since there exists surface states density for semiconductors,there will be a modulation of the depletion layer near the surface when semiconductors are put in contact and separation dynamically.There are four current peaks: two of them are attributed to the CE effect and determined by the surface potential difference between two tribo-materials,while the other two current peaks are associated with the junction modulation effect and determined by the charging and discharging processes of the depletion regions.The electron affinity difference between polymer and semiconductors can generally vary considerably,resulting in the induced current large enough to override the current peaks caused by junction modulation effect.Thus,whether the four current peaks are all observable or not depends on the relative strength of the amplitudes.3.Finally,we investigated the output characteristics and charge transfer mechanism of the semiconductor – metal TENGs.The experimental results showed that the periodic contact and separation between semiconductor and metal was accompanied by the formation and destruction of the Schottky junction,and the majority of carriers in the semiconductor material are periodically trapped and released by the surface state.Therefore,the combination of CE effect and junction modulation effect also induced four current peaks.Due to the relatively small surface potential difference between the semiconductor and metals,the current peaks caused by these two effects are comparable and can be easily observed.In summary,we outlined the output characteristics and the theoretical mechanisms of all types of materials undergoing periodic contact-separation motions,and enriched the theoretical model of TENGs.This provides a new strategy for the design and preparation of high-performance TENGs and TENGs that can satisfy the needs of various complex practical application scenarios.