The Efficient Preparation And Optical Properties Of Copper-based And Silver-based Metal Halides

Lead halide perovskite materials have been considered as effective materials for optoelectronic applications and are widely developed in the field of optoelectronic devices due to their unique properties such as suitable band gap,large absorption coefficient,high defect tolerance and high charge carrier mobility.In spite of their attractiveness,lead halide perovskites have to face many challenges such as the lack of stability upon prolonged exposure to light,humidity,or high temperature,and,especially,the intrinsic toxicity of lead.Recently,since unique properties such as high luminescence intensity,good thermal stability,large Stokes displacement,minimum self-absorption,low cost and non-toxicity,the 0D/1D orthorhombic Cs-Cu-X(X=Cl-,Br-,I-)material has wide applications in ultraviolet light detection,scintillator,light emitting diode(LED),pressure sensing,transparent solar concentrator and other optoelectronic devices.Cs-Ag-X(X=Cl-,Br-,I-)with the orthorhombic phase presents a similar 0D/1D/2D crystal structure of Cs-Cu-X at the molecular dimension,which has a potential application prospect in the field of photonic crystals and ionic conductivity.However,it still has problems in the efficient preparation of Cs-Cu-X and exploring the factors affecting its phase transformation.In addition,there is no systematic study on the optical properties of Cs-Ag-X.Due to the lack of knowledge of optical properties of Cs-Ag-X,its development in the applications of optoelectronic devices is limited.More importantly,there are still great challenges in the field of preparing all-inorganic scintillator devices with high light yield and fast response time.Because of these problems,the main contents of this paper are as follows:In the second chapter,a series of Cs-Cu-X(X=Cl-,Br-,I-)with large Stokes displacement,broad full width at half maximum were synthesized by means of solid phase grinding.The photoluminescence band can cover range from blue-violet to yellow light via simply adjusting the stoichiometric ratio of Cs-X and Cu-X.The PLQY of Cs3Cu2Cl5 and Cs3Cu2I5 was close to 100%.Meanwhile,the results of DFT theoretical calculation confirm the composition and size of the band in each configuration,which further supported the accuracy of optical characterization.In addition,the reversible in situ conversion between Cs3Cu2I5 and Cs Cu2I3 crystal structures was achieved by the induction of water.Interestingly,the conversion of the structure was also accompanied by the conversion of photoluminescence from yellow(Cs Cu2I3)and blue(Cs3Cu2I5).When the air humidity is 70%,the water response time of Cs3Cu2I5 film was 30 seconds and it had good repeatability.In the third Chapter,Due to the limitation of Cs-Cu-X photoluminescence spectrum can not achieve full spectrum coverage,Ag ions with larger ionic radius are introduced to replace Cu ions with relatively smaller radius in order to achieve a wide range of spectrum coverage.We efficient and universal synthesized a series of stable Cs-Ag-X(X=Cl-,Br-,I-)with large Stokes displacement and broad full width at half maximum by means of solid phase ball milling method.The PLQY was 17%-68%,and the photoluminescence spectrum of Cs-Ag-X achieved full visible spectrum coverage from ultraviolet to near-infrared.The peak position of the emission band was determined by optical characterization,in which Cs2 Ag Cl3 was at 397 nm(blue-purple),Cs Ag2I3 was at 468 nm(blue),Cs2 Ag Br3 was at 524 nm(green),and Cs2 Ag I3 was at595 nm(yellow).Cs Ag Cl2 was at 620 nm(orange yellow)and Cs Ag Br2 was at 820 nm(near-infrared).By changing the halogen composition of Cs Ag(Clx/Br1-X)2,the emission peak of Cs Ag(Clx/Br1-X)2 can be adjusted continuously from Cs Ag Cl2(620nm)to Cs Ag Br2(820 nm).Cs-Ag-X had a fast response time of 11.8-135 ns and excellent X-ray absorption capacity.Under X-ray excitation,Cs-Ag-X had scintillation properties,among which the photoyield of Cs Ag Cl2 is 8400 photons /Me V.In the fourth chapter,a series of x Cu: Cs2 Ag I3 compounds were synthesized and the optimal doping concentration of Cu ion(I)was determined to be 0.66 %.The0.66%Cu: Cs2 Ag I3 single crystal with broadband emission and 1D morphology shows bright blue-green fluorescence(photoluminescence quantum efficiency is 73%),and the emission peak was 488 nm.In the application of X-ray scintillator,Cu: Cs2 Ag I3have a good X-ray absorption capacity,which was superior to commercial scintillator Tl:Cs I in the medical detection range of 25-33 ke V,which has no self-absorption properties,has a high light yield of 27000 photons /Me V with a minimum detection line of 6.69?Gy S-1.More importantly,0.66%Cu: Cs2 Ag I3 scintillator exhibited a fast response time of nanosecond,which provides a broad prospect for the realization of scintillator dynamic X-ray imaging.