Stability And Application Device Exploration Of All-inorganic Perovskite CsPbBr₃ Nanocrystals

All-inorganic perovskite materials refer to a class of materials with ABX₃ crystal structure,where A is an inorganic group.Due to the higher defect tolerance than traditional luminescent materials,they usually exhibit excellent optical properties,such as narrow emission peak and high photoluminescence quantum yield(PLQY).Now,perovskites have been widely used in light emitting diode(LED),laser and X-ray imaging fields.However,they will generate intrinsic defects during the synthesis process.The existence of defects makes their stability in water,light,heat and other environments poor.Therefore,to realize its commercial application,we still need to further improve its structural stability.This topic takes Cs Pb Br₃ nanocrystals(NCs)as an example,starting from its synthesis route,optimizing the synthesis scheme,passivating its surface defects,thereby improving its stability and exploring its passivation mechanism.The specific content is:(1)The first is to solve the problem of water stability of perovskite Cs Pb Br₃ NCs.Here we use a water-treatment method to induce the phase transformation of Cs₄Pb Br₆ NCs into Cs Pb Br₃ NCs.The surface of the obtained Cs Pb Br₃ NCs is rich in a layer of short-chain hydroxyl(OH)ligands.The presence of OH ligands makes perovskite exhibit excellent water stability.The prepared Cs Pb Br₃ NCs are successfully applied to white LED(W-LED).(2)Although the water treatment method provides ligand protection,the contact time between the sample and water is longer during the phase transition,and the surface of the prepared Cs Pb Br₃ NCs has a large number of defects.Therefore,we adopt a cooperative effect of water and photon energy to accelerate the phase transition process,thereby further optimizing the structure of Cs Pb Br₃ NCs.After introducing 365 nm light,the phase change time of water treatment is reduced from48 hours to 5 hours.The surface defects of the prepared Cs Pb Br₃ NCs are reduced,and they still have excellent photostability under 800 nm femtosecond laser continuous irradiation.(3)In the process of cooperative effect of water and photon,the presence of water makes it difficult to control the phase transition process,which is not conducive to further optimizing the crystal structure and improving heating stability.Here,we adopt a solution-process annealing strategy with a relatively easy process to improve the crystal structure.The defect of Cs Pb Br₃ NCs obtained is significantly reduced and the structure is more complete.The annealed NCs have higher heating stability,light stability and water stability.In addition,the annealed NCs scintillator exhibit long-term stable(?3600 s)X-ray imaging at a commercial radiation dose(1 m Gy/s).