Research On Preparation And Application Of Flexible Self-powered System Based On Wide Bandgap Oxides

With the gradual popularization of the Internet of Things and artificial intelligence concepts,wearable flexible electronic devices have shown an explosive growth trend in recent years.Different from semiconductor devices on traditional rigid substrates(such as silicon,sapphire,glass),flexible electronic devices are widely used in biomedical monitoring,environmental monitoring,communication,flexible display,and human-computer interaction due to their flexibility,low mass,good biocompatibility,and adjustable mechanical properties,which has been profoundly affecting our daily lives in various fields.Traditionally,the energy of flexible electronic devices is generally derived from batteries.Compared with the miniature flexible electronic devices,these batteries are much heavier and bulkier.Besides that,their storage power is limited,requiring users to replace or charge the batteries frequently.What's more,the chemical substances contained in the batteries may leak during the use of wearable electronic devices,causing harm to human health and the environment.Therefore,it is urgent to develop new type of power-supply devices with light weight,long sustainability and smart portability.Triboelectric Nanogenerator(TENG)converts mechanical vibration energy in the environment into electrical energy because of the triboelectric effect and electrostatic induction effect.Its low operating frequency,low production cost and good biological compatibility make it suitable for the application scenarios of the wearable flexible electronic devices.To improve the output power density of TENG,preparation of the wrinkle structure on the surface of Polydimethylsiloxane(PDMS)was firstly carried out.ZnO film was grown on the surface by radio frequency magnetron sputtering.Due to the weak self-heating effect during the sputtering process and the obvious difference in Young's modulus and thermal expansion coefficient between ZnO and PDMS,irregular wrinkled structure on the surface of the PDMS film will spontaneously form.By changing the sputtering thickness of the ZnO film,the feature of the wrinkle structure can be effectively controlled.Compared with TENG prepared using flat PDMS film,the open circuit voltage(Voc)and short circuit current(Isc)of TENG using wrinkled PDMS have been significantly improved,and the output power density has increased by nearly two orders of magnitude after optimization.Furthermore,finite element simulation method has been used to confirm that the surface microstructure is beneficial to the improvement of the output performance of TENG.In addition,due to the limitation of its working principle,TENG can only work in dynamic mode,which further limits its application in flexible electronic devices.A new strategy of energy harvesting scheme in static mode has been proposed,based on which a flexible Ga₂O₃ deep ultraviolet detection system driven by environmental electromagnetic radiation has been realized.A Ga₂O₃-based metal-semiconductor-metal ultraviolet photodetector and an energy harvesting component including a metal receiving electrode and a full-wave bridge rectifier based on ZnO field effect diodes have been prepared on the flexible polyethylene naphthalate(Polyethylene naphthalate,PEN)substrate via traditional micro-fabrication technique.The environmental electromagnetic radiation energy can be collected through human hand's contact with the receiving electrode and rectified by the bridge circuit,which can be directly supplied to the Ga2O3 deep ultraviolet detector.The photoresponsivity can reach 0.1 A/W,which is generally one to two orders of magnitude higher than other junction self-powered ultraviolet detectors.In addition,the integrated system can still maintain good detection performance under bending conditions,demonstrating its application prospects in the field of wearable self-powered ultraviolet detection.Except the 50 Hz low-frequency electromagnetic waves generated by high-voltage lines,substations,general household appliances,and experimental equipment,environmental electromagnetic radiation also includes a wealth of high-frequency electromagnetic waves ranging from MHz to GHz,which are widely existed in mobile phones,communication base stations,WIFI routers,microwave ovens.In order to improve the collection efficiency of such high-frequency radiations,the frequency response performance of the field-effect diode,which is the core component of the rectifier bridge,has been optimized by constructing a dual channel layer,where a thin IGZO with low-resistance is inserted to effectively passivate the interface defects between the channel layer and the dielectric layer and improve the stability of the diode.As a result,the annealing and activation process,which is necessary for the single IGZO channel,are avoided,agreeing very well with the low-temperature manufacturing process for flexible electronics.An overlap structure between the gate and the drain is designed with the optimization of the device size,leading to the enhancement of the gate control ability,which significantly improves the frequency response performance.Furthermore,using the IGZO field effect diode with dual channel layer,a rectifier bridge has been built and then connected parallelly with a capacitor made of ionic liquid to realize an integrated circuit with the function of rectification and filtering.Through this integrated system via the coupling of the human body,the environmental radiation energy can be efficiently collected and stored in the capacitor,which can successfully lighten the commercial LED bubble.In summary,focusing on the energy harvesting and management system urgently needed for flexible electronic devices,a simple preparation method of the PDMS film with wrinkle structure has been developed,which can effectively improve the output power density of the dynamic energy harvesting device TENG.Further,a new static environmental electromagnetic radiation energy collection mode is proposed,and an integrated self-powered deep ultraviolet detection system using ZnO field effect diode rectifier bridge,Ga₂O₃-based deep ultraviolet detector and metal receiving electrode is constructed.Finally,the frequency response of the field effect diode is further optimized by introducing the IGZO double-channel layer,making it more suitable for high-frequency and low-voltage environmental radiation energy harvesting.