Research On Flexible Piezoresistive Pressure Sensor Based On Perovskite

Piezoresistive pressure sensor has a very attractive market prospect because of its strong adaptability and wide application scenarios.Although the performance of piezoresistive pressure sensors has been improved rapidly,there are still problems such as low precision and narrow pressure measurement range,which are difficult to meet the requirements of high precision and wide range of industrial requirements.In order to improve this situation,the development of a new type of high stability,strong environmental adaptability of high performance pressure-sensitive materials,for the development of high precision,good stability of the pressure sensor is very important.In recent years,metal halide perovskite materials have become excellent pressure-sensitive materials due to its soft lattice,high defect tolerance and good carrier transport.Currently,the research on perovskite pressure-sensitive materials is mainly non-flexible,which is difficult to be applied to wearable and other flexible electronic devices.Without solving this problem,in this thesis,by embedding perovskite nanocrystal into flexible polymer film,high performance flexible piezoresistive perovskite pressure sensitive film was realized.Specifically,the following research work was carried out in this thesis:（1）Porous in situ perovskite flexible pressure sensitive film.In the experiment of this chapter,the flexible pressure-sensitive film based on MAPb Br₃ perovskite quantum dots was prepared by in-situ preparation technology,and its stability information was obtained through characterization of its optical properties.Then,the sandwich structure of high flexibility and high pressure sensitive MAPb Br₃/PVDF/TFSI/EPDM flexible pressure sensor was prepared by spinning coating method.The porous structure in the pressure-sensitive material leads to the quantum tunneling of carrier between perovskite quantum dot and polymer under pressure,which makes the piezoresistive sensor with perovskite quantum dot have excellent piezoresistive performance.It has high sensitivity(1.13k Pa^-1),good ohm performance,excellent stability,fast recovery response time（200ms）,and can maintain high sensitivity characteristics under low stress（0.13k Pa）and high stress（25k Pa）,indicating that the sensor has excellent practical value.In addition,according to various demonstrations of monitoring human movement,the pressure sensor proved to be effective in monitoring human pulse,subtle changes in facial muscles and real-time changes in joint movement.（2）In situ stretchable perovskite flexible pressure-sensitive film.Perovskite composite films were prepared by in situ solution method and used as pressure sensitive materials for pressure sensors.When the flexible pressure sensitive film has good stretchability,it can better fit with the flexible substrate,prolong the service life,better experience.Therefore,Tpus with good stretchability and adhesion are used to mix perovskite and PVDF to prepare PVDF/TPU/PVSK flexible pressure films,which have better adhesion to flexible substrates than PVDF/TFSI/PVSK.Better adhesion enables the PVDF/TPU/PVSK pressure sensor to achieve a sensitivity of 0.85 k Pa^-1 in the linear range of 0～25 k Pa and 0.744 k Pa^-1 in the linear range of 25～60 k Pa.It has a response time of 87.75ms and an excellent response time of 102.05ms.At the same time,the device has good working stability.The preparation of the flexible film is of great significance for the realization of high performance pressure sensor.It provides a new scientific idea for the design of high precision and high stability perovskite quantum dot flexible thin film pressure sensor.（3）Non-lead flexible perovskite pressure-sensitive film.At present,perovskite pressure sensors are mainly lead-based perovskite with toxic content.In this chapter,by controlling the crystallization process of TPU and MASn Br I₂ separated by DMF evaporation,MASn Br I₂/TPU non-lead perovskite flexible pressure-sensitive films were prepared.The size and spatial distribution of perovskite in pressure-sensitive materials were uniform.By changing the composition ratio of halides,a flexible film with high thermal stability and good water resistance was obtained.Non-lead perovskite flexible pressure sensitive films prepared with perovskite material MASn Br I₂ as pressure sensitive filler and TPU as matrix have high sensitivity S=0.796k Pa^-1,excellent response-recovery time and good stability.Subsequently,the influence of pressure on carrier transport was revealed by means of experimental characterization,and its excellent piezoresistive performance was verified by experiments.At the same time,the pressure sensor has excellent detection capabilities for respiratory airflow,pulse and finger joint curvature.The research of the above novel flexible pressure-sensitive materials brings new opportunities for flexible pressure sensors,which is of great significance in the fields of health monitoring,human-computer interaction,intelligent electronic wearable devices,etc.