Study On The Structural Phase Transition And Optical Properties Of Sb³⁺ Doped Lead-free Metal Halides Powders

Due to its excellent optical properties,lead halide perovskites have huge potential applications in light-emitting diodes(LEDs)for advanced displays and general lighting.However,lead halide perovskites are toxic and have poor environemental stability,which limited their applicatins.Lead-free metal halide perovskites may replace lead halides due to their low toxicity,good stability and excellent optical properties.Lead-free metal halide perovskites show good compositional and emission tunability after their component engineering,which makes them for a wide range of potential applications.How to effectively control their crystal structure transformation and composition of the lead-free metal halide perovskite is very important to tune their physical properties.In this dissertation,several lead-free metal chloride perovskite Sb³⁺doped(Cs_1-xRb_x)₂In Cl₅·H₂O,(Cs_1-xRb_x)₃In Cl₆ and Cs₂KIn Cl₆ have been studied.by adjusting the feed ratio or reaction solvent of the prepared lead-free metal chlorides,the reversible crystal structural transition between A₂In Cl₅·H₂O(A=Cs,Rb)and A₃In Cl₆(A=Cs,Rb)was proved;the reversible crystal structural change between A₂In Cl₅·H₂O(A=Cs,K)and Cs₂KIn Cl₆,The optical properties and stability of these lead-free metal chlorides have also been systematically studied.The research achievements are listed as follows:(1)When the hydrochloric acid(HCl)is selected as the reaction solvent,when the feed ratio Cs/Rb>2:1,Sb³⁺doped(Cs_1-xRb_x)₂In Cl₅·H₂O is synthesized.XRD,EDS and XPS results proved the formation of Sb³⁺:(Cs_1-xRb_x)₂In Cl₅·H₂O alloy.Its photoluminescence quantum yield(PLQY)is 75.7%,and emission peak is about 612 nm,and has good water and oxygen stability and thermal stability.Finally,Sb³⁺:(Cs_1-xRb_x)₂In Cl₅·H₂O powders were used to fabricate a light-emitting diode(LED)device.After working for 100 hours at a driving voltage of3.5 V,the device luminescence intensity still maintained 89.1%of its initial value.(2)When hydrochloric acid(HCl)is selected as the reaction solvent,when the feed ratio Cs/Rb<2:5,Sb³⁺doped(Cs_1-xRb_x)₃In Cl₆ is synthesized.XRD,EDS,XPS,results show that the formation of Sb³⁺:(Cs_1-xRb_x)₃In Cl₆ alloy,with a luminescence peak at about 510 nm and a PLQY of 90.86%.However,when anhydrous methanol(Me OH)is used as the reaction solvent,only the structure of Sb³⁺:(Cs_1-xRb_x)₃In Cl₆ is formed at all Cs/Rb feed ratios.In addition,between Sb³⁺:(Cs_0.67Rb_0.33)₂In Cl₅·H₂O and Sb³⁺:(Cs_0.67Rb_0.33)₃In Cl₆,a reversible crystal structure change was realized by immersing the prepared product into anhydrous methanol and hydrochloric acid in sequence,with a new green/yellow reversible emission switching,provides a way for the structural design and luminescence control of doped metal chlorides materials.(3)When hydrochloric acid(HCl)is selected as the reaction solvent,when the feed ratio Cs/K<1:1,Sb³⁺doped Cs₂KIn Cl₆ is synthesized.Sb³⁺:Cs₂KIn Cl₆has tetragonal symmetry,exhibits green light emission,with PLQY as high as98.1%.Moreover,adding an appropriate amount of KCl to the prepared Sb³⁺:(Cs_1-xK_x)₂In Cl₅·H₂O can generate Sb³⁺:Cs₂KIn Cl₆;adding an appropriate amount of Cs Cl and In Cl₃ to the prepared Sb³⁺:Cs₂KIn Cl₆ lead to Sb³⁺:(Cs_1-xK_x)₂In Cl₅·H₂O,realizes a zero-dimensional and three-dimensional reversible structural transition,with a new green/yellow reversible light-emitting switching.The light-emitting diodes of Sb³⁺:Cs₂KIn Cl₆ show excellent optical parameters,which will promote the diversified applications of environmentally stable perovskites in photonics and optoelectronics.