Study On The Synthesis And Mechanism Of Mn Doped Inorganic Perovskite Quantum Dots

Lead halide perovskite quantum dots（PQDs）have been paid a lot of attention due to their high quantum yield,tunable luminescence and easily to synthesize.Some unique photoelectric properties can be introduced into PQDs via a doping process.Comparing to undoped counterpart,more appropriate luminescent and electric properties can be achieved.Specially,as a kind of divalent cation,Mn²⁺ ions are easy to substitute Pb²⁺ ions and dope into PQDs.Furthermore,Mn²⁺ can be facilely sensitized by perovskite host and abundant the color of luminescence.In this paper,we focus on synthetize and luminescent properties of Mn²⁺ doped PQDs and mechanization of synthesis process.The main works are as follows:1.Here we demonstrate that dynamic halogen exchange can effectively open up [Pb X6]4-octahedrons and enable fast Mn-to-Pb cation exchange at room temperature in a few seconds.Importantly,Cl concentration rather than Mn one is demonstrated to be a dominant factor for cation exchange,where different Mn²⁺/Clsalts can be adopted as Mn/Cl sources and Cl-to-Cl or Cl-to-Br anion exchange is the necessary prerequisite.Such a facile synthesizing method can lead to the feasibility of tuning emissive colors for the Mn-doped Cs Pb（Cl/Br）3 NCs by controlling both cation and anion exchanges.2.Effective Mn²⁺ doping in a CsPbCl₃ lattice utilizing manganese acetate and trimethylchlorosilane is achieved via a one-pot hot-injection synthesis method.The Mn doping concentration are highly dependent on trimethylchlorosilane content.A new doping mechanism is proposed,where the incorporation of Mn²⁺ into CsPbCl₃ is achieved via directly inserting [Mn Cl6]4-octahedra into the perovskite structure during the nucleation/growth processes instead of Mn-to-Pb cation exchange.Accordingly,increasing Cl-content in the reaction solution indeed promotes the doping of other divalent transition metal ions such as Ni2+,Cu2+ and Zn2+ in CsPbCl₃ and improve the quantum yield of CsPbCl₃ nanocrystals up to ～20% compared to the undoped counterparts（～1%）.3.Here,a halogen-hot-injection strategy is developed to prepare Mn:Cs Pb（Cl0.6Br0.4）3 NCs with the maximal PLQY of 65%.With this method,intense blue narrowband emission from excitonic recombination and orange broadband emission from Mn²⁺ 4T1→ 6A1 transition can be simultaneously achieved.The competitive luminescence between perovskite NCs and Mn²⁺ dopants is systematically investigated by controlling the injected halogen types and ratios.As a proof-of-concept experiment,the present Mn²⁺-doped Cs Pb（Cl/Br）3 perovskite NCs with highly efficient dualcolor emissions are demonstrated to be applicable as color converter in UVexcitable solid-state lighting.