Synthesis And Gas/Humidity Sensing Properties Of Te,Sb,In-Based Halide Perovskites

With the progress of science and technology and the improvement of living standards,gas and humidity sensors have become an important research topic.The increasing healthcare in demand modern society has created a huge market for intelligent devices that enable early diagnosis and prevention of diseases.Sensors are the core components of intelligent equipment,which is used to detect volatile organic compounds（VOCs）related to human health and identify characteristics related to human activities,including temperature,pressure and humidity.Therefore,it is important to develop humidity sensors that can identify breathing behavior relevant to disease detection,and chemical gas sensors relevant to early disease diagnosis to enable non-implantable body health management.Compared with other sensors,chemical sensors have simple structure,small size,low power consumption and low preparation cost,which are more helpful to improve the portability of sensors.Metal halide perovskites（MHPs）materials have tunable band gap,high electron and hole carrier mobility,long carrier transport distance,and stable crystal structure.MHPs are widely considered as promising sensing materials in the field of sensing devices.In recent years,the research on metal halide perovskites has achieved great progress.However,due to the instability and inherent toxicity of lead cation in perovskite itself,the long-term performance of the sensor is far from satisfactory.In this work,we focus on more stable internal structure of Te based perovskite Cs₂Te X₆（X=Cl,Br,I）and Sb based perovskite Cs₃Sb₂X₉（X=Cl,Br,I）,to investigate the effect of halogen elements on the performance of perovskite gas/humidity sensing.A more stable noble metal Ag-containing halide double perovskite Cs₂Ag In Cl₆ was synthesized by a simple hydrothermal method.It achieves excellent sensing performance such as high selectivity,high sensitivity and low detection limit for gas,providing a new direction for perovskite materials in the field of gas humidity sensing.The specific results are as follows:（1）The hydrothermal synthesis of perovskite was carried out by introducing different acid ions in the synthesis of vacancy-ordered perovskite Cs₂Te X₆ with different halogen elements（X=Cl,Br,I）.Characterization of the Cs₂Te X₆microstructure,morphology,specific surface area and surface defects.Cs₂Te Cl₆ is rich in surface defects.By comparing the humidity sensing properties,Cs₂Te Cl₆ has ultra-fast response time(τ_res<1 s).The excellent sensing performance is mainly attributed to the large number of active sites on the surface of Cs₂Te Cl₆.In addition,the Cs₂Te Br₆humidity sensor shows great potential in non-contact human humidity detection.This work provides new candidate materials for humidity sensors and further provides a new direction for MHPs in human health detection.（2）In a simple hydrothermal synthesis process,the perovskite Cs₃Sb₂X₉（X=Cl,Br,I）with different halogen elements absence was synthesized by changing the acid radical ions.The materials were characterized by XRD,SEM,EDS,UV-Vis,PL and XPS.Cs₃Sb₂Br₉ showed a response value of 3.89 to 20 ppm dimethylamine（DMA）at room temperature,with shorter response recovery time,good repeatability and stability.The excellent DMA sensing performance is mainly attributed to the large number of defects on the surface of Cs₃Sb₂Br₉.（3）Ag-rich halide double perovskite Cs₂Ag In Cl₆ was synthesized by hydrothermal method.The structure,morphology,optical properties and elemental composition of the materials were systematically analyzed.Cs₂Ag In Cl₆ exhibits excellent gas sensing properties,the response is up to 68 for DMA（200 ppm）at room temperature,a response recovery time of only 270/64 s,and a low detection limit of 30 ppb,which has great prospects for low concentration DMA detection.In addition,it was confirmed by gas chromatography that the DMA gas adsorbed on the surface of Cs₂Ag In Cl₆ material was partially oxidized at room temperature.The gas sensing mechanism can be explained as the combined effect of abundant Cl vacancies on the surface and Ag-induced chemical sensitization and electron sensitization.In summary,this paper explores the potential application of metal halide perovskites in the field of gas/humidity sensors by synthesizing perovskites of different structural types.It expands new ideas for portable human health detection at room temperature in the future.