Solvothermal Synthesis Of Transition-Metal-Doped Inorganic Perovskite Nanocrystals And Their Properties

As a new type of semiconductor nanomaterials,inorganic lead halide perovskite CsPbX₃(X=Cl,Br,I)nanocrystals(NCs)show promising application prospects in various optoelectronic fields owing to their excellent optoelectronic properties.Doping is an extensive and effective method for the modification of semiconductor materials,which can improve their properties or endow them with novel optical,electrical and magnetic characteristics.In recent years,many studies on the doping of inorganic perovskite NCs have shown that the doping of metal ions in inorganic perovskite NCs can significantly improve their properties.However,controllable synthesis of high-quality metal-doped perovskite NCs with precisely tunable morphology and properties still remains challenging.Solvothermal synthesis can provide a mild reaction environment,making it easier to control the growth process of NCs.In this paper,a modified solvothermal synthesis strategy is applied to the preparation of transition-metal-doped perovskite NCs,and the controlled synthesis of doped perovskite NCs is realized.The main contents are as follows:(1)Mn-doped CsPbCl₃ NCs were successfully synthesized by solvothermal method.The morphology and optical properties of perovskite NCs can be precisely controlled.The incorporation of Mn²⁺introduces an energy transfer pathway from CsPbCl₃ host to dopant,which enhances the d-d transitions(⁴T₁-⁶A₁)of the Mn²⁺and generates new Mn²⁺orange luminescence.Mn-doped CsPbCl₃ quantum dots(QDs),nanoplatelets(NPLs)or their mixtures can be obtained respectively by changing the amount of organic ligands.The doping ratio,photoluminescence(PL)indensity and emission peak position of Mn-doped CsPbCl₃ NCs can be accurately controlled by adjusting Mn-to-Pb molar feed ratio(5:1-10:1)or solvothermal reaction time(3-12 h).In addition,Mn-doped CsPbCl₃ QDs and NPLs both show size-dependent quantum confinement effect,which can be confirmed by the change of exciton emission peak with their size.(2)Ni-doped CsPbCl₃ QDs were suceessfully obtained by solvothermal method.The incorporation of Ni²⁺ions into CsPbCl₃ QDs effectively reduces the defect states and restrains the nonradiative recombination rates without introducing new emission peaks,thereby significantly improving the PL quantum yield(QY)of CsPbCl₃ QDs.The Ni²⁺ions enhance the PLQY of CsPbCl₃ QDs from 1.9%to 14.2%.Moreover,the structure,doping ratio and optical properties(absorption,emission,PL lifetime and PLQY)of Ni-doped CsPbCl₃ QDs can be precisely controlled by adjusting solvothermal reaction temperature(160-180�C),reaction time(1 min-6 h)and Ni-to-Pb molar feed ratio(2:1-4:1).(3)Cu-doped CsPbX₃(X=Br or Br/Cl)QDs were successfully prepared by solvothermal method.The introduction of Cu²⁺improves optical properties and stability of CsPbX₃ QDs.The effects of Cu-to-Pb molar feed ratio(0.25:1-2:1)and solvothermal reaction time(0.5-3h)on the size,doping ratio,emission peak position,PL lifetime and PLQY of Cu-doped Cs Pb Br₃ QDs were systematically investigated.The PLQYs of Cu-doped Cs Pb Br₃ and Cs Pb(Br/Cl)₃ QDs maintain 93%and 85%of the original value respectively after gradually heating to 65�C,showing excellent thermal stability.The high stability of Cu-doped QDs can be attribute to the improvement of short-range order in the crystal and the formation of Cu-X bonds with higer bond energy via the incorporation of Cu²⁺ions.