Preparation And Properties Of Stabilized Perovskite Quantum Dots With Layered Double Hydroxide Nanosheets

In the past few years,metal halide perovskite quantum dots（PQDs）have received great attention from researchers due to their excellent optical properties and broad application prospects.Because of their adjustable band gap,high photoluminescence quantum efficiency,long exciton lifetime and high carrier mobility,PQDs has been widely used in solar cells,high-efficiency light-emitting diodes,high-sensitivity photodetectors and other fields.Although PQDs have such broad application prospects,they also have shortcomings such as poor stability and low synthesis yield,which severely limits their further applications.In order to overcome these shortcomings of PQDs,researchers are committed to developing some effective strategies to improve the optical performance and stability of PQDs.Among them,the use of organic or inorganic matrix to encapsulate PQDs is a very effective method.Due to the unique microscopic morphology,delicate electronic structure and relatively large specific surface area,layered double hydroxides（LDHs）have very broad prospects in many fields such as photoelectricity and catalysis.In this paper,we use LDH nanosheets and PQDs to significantly improve the stability of perovskite.The detailed work includes the following two parts:In the first part,LDH nanosheets are used as the protective substrate,and perovskite quantum dots are grown in situ on the surface by a one-pot method at room temperature to prepare LDH/CsPbBr₃ composites on a large scale.The synthesized composite material shows good green light emission,high solid photoluminescence quantum yield PLQY（～41%）,narrower half-value width（FWHM～20nm）and longer fluorescence lifetime.Because the LDH nanosheet has a unique two-dimensional structure and excellent adsorption capacity for Pb²⁺and Cs⁺,it is conducive to the firm anchoring of the PQDs on the LDH nanosheet,preventing the aggregation of PQDs,and providing significantly enhanced humidity stability,thermal stability and excellent light stability of LDH/CsPbBr₃ composites.In addition,the assembled WLED based on LDH/CsPbBr₃ composite also shows excellent performance.This provides new opportunities for the application of perovskite in the field of optoelectronics.In the second part,the surface of LDH nanosheets was grafted with hydrophobic polymer chains by reversible addition-fragmentation chain transfer（RAFT）radical polymerization method,and a cross-linked network was constructed through quaternary ammonium salt reaction to prepare cross-linked polymer functionalized LDH（LDH-CP）.Subsequently,a simple ligand-assisted co-precipitation（LARP）method was used to grow PQDs on the surface of LDH-CP at room temperature to prepare LDH-CP-CsPbBr₃ composites.The synthesized LDH-CP-CsPbBr₃ composite shows bright green luminescence,with a narrow FWHM（～25nm）and a high solid photoluminescence quantum yield（PLQY）（～51.9%）.With the double protection of the unique two-dimensional structure of LDH nanosheets and the hydrophobic polymer cross-linked network,the LDH-CP-CsPbBr₃ composite is endowed with excellent water stability,thermal stability and light stability.In addition,the WLED based on the LDH-CP-CsPbBr₃ composite also shows great white light emission and excellent device performance,proving that the composite material we prepared has great development potential in lighting and display applications.