Preparation Of Halide-rich Hybrid Perovskite Sensing Materials And Their Applications In Flexible Wearable Devices

Organic-inorganic perovskites are promising optoelectronic semiconductor materials with photoelectric applications.It is known that the luminescence of perovskites is highly sensitive to hydron due to its low moisture resistance of crystal structure,indicating it may have a potential application on environment-sensing.At present,due to the limited Varshini electron-phonon coupling theory of perovskite materials,all photoluminescence（PL）performances of almost all perovskites are negative temperature sensitivity to temperature responsiveness,which will not only reduce the detection sensitivity of the device but also affect the stability of the device.From the perspective of application design,the material with positive temperature response is more in line with the design and application of the device,which is positively helpful for improving sensitivity and data acquisition and analysis,but a perovskite temperature-sensitive material with positive temperature sensitive and stable sensing has not yet been developed.Based on this background,a new composite of perovskite/PEO（PPC）was developed by optimizing the drying method,precursor composition,and surface coating perovskites to achieve stable environment-PL sensing applications.The initial perovskite MAPb Br₃ with a small size,complete crystal structure,and PL was prepared by supercritical drying method.A perovskite matrix composite perovskite-based compound with high PL performance was prepared by passivating MAPb Br₃ crystal defects by excessive MABr.Polyethylene oxide（PEO）with hydrophilic and compliant polyethylene oxide（PEO）was added to clad perovskites,and the perovskite sensitivity was improved at the mass ratio of PEO/PBC=0.75:1,and an environmental sensing composite PPC with solution processability was prepared.On this basis,the performance and mechanism of humidity sensing are studied.Sensitivity:Due to the coating effect of PEO,the PL of PPC showed negative humidity sensitivity in the range of 10%～50%relative humidity（RH）,with a sensitivity of 1.670.Stability:PPC still maintains performance and structural stability under 22 RH cycles,PL only decreases by 28%,and the crystal structure can be restored under low humidity（RH 10%）.Humidity sensing mechanism:Under humidity stimulation,the O-H of PEO interacts with the N-H of the MA⁺group to adsorption-resolve,thereby preventing the invasion of O-H in water molecules.Researching the performance and mechanism of temperature sensing.Sensitivity:In the PBC stage,MABr/MAPb Br₃（MP）is MP71,and PL is increased by 2 orders of magnitude;In the PPC stage,the MP71@PEO has the highest temperature sensitivity,and the PPC PL is increased by 4 orders of magnitude compared with MAPb Br₃.In the range of room temperature25～40°C,PPC has positive temperature sensitivity of 4.25%C^-1.Stability:PPC still maintains performance and structural stability under 9 temperature cycles,PL only decreases by 48%,and the peak intensity of crystal characteristic crystal plane（110）also has positive temperature sensitivity characteristics.Temperature sensing mechanism:Under vacuum nitrogen,the contribution of MABr and PEO to PPC temperature sensitivity was analyzed,MABr was responsible for improving fluorescence performance,PEO was responsible for providing sensitivity and stability,and PPC showed negative temperature sensitivity characteristics,which proved that PPC followed the electron-phonon coupling theory.However,under the condition of keeping the indoor RH 50%constant,due to the hydrophilicity of PEO,the negative temperature coefficient properties of PPC solubility at room temperature are proposed,and the"temperature-confined microcrystalline-PL"sensing mechanism is proposed:when under different temperature stimuli,the microcrystalline perovskites are dissolved（cooled,solubility increased）and crystallized（heated up,solubility decreased）in the confinement structure of the matrix material so that the PL of the perovskites shows a positive temperature response so that it shows the sensing characteristics of positive temperature sensitivity.Based on the compliance of PEO,based on sensitivity,and solution processability,the application of fluorescence anti-counterfeiting humidity sensing is realized.Based on the transmission change of light by PPC film under macro temperature change,the thermochromic smart window is realized.Theτ_avgis 81.68 ns based on the positive temperature sensitivity characteristics of PPC PL lifetime,and the wearable portable temperature sensor with information encryption function in the time dimension is realized with 3D printing technology,and the PL lifetime is more than 8 times that of the traditional fluorescent encryption device in the time dimension.In addition,it also has broad application prospects in architectural decoration,logos,trademarks,and other aspects.