Synthesis And Characterization Of Mn-doped Cesium Lead Halide Perovskites Nanocrystals

In recent years,perovskite halide nanocrystals have excellent optical and optoelectronic properties due to their unique"defect tolerance"characteristics,and have broad application prospects in the field of light-emitting diodes and solar cells.Luminescent doped semiconductor nanocrystals are one of the hotspots of current research.Doping can broaden the luminescent range of nanomaterials and provide a unique way to design solid-state lighting and light collecting materials.What is important is Mn²⁺is one of the most commonly used transition metals.Doping of Mn²⁺can introduce many new optical,electrical and magnetic properties.So,Like other semiconductors,doping has been widely used in CsPbX₃ NCs.According to the literature report,Mn²⁺ions can be easily doped into CsPbCl₃ NCs by hot-injection method.However,on the one hand,although Mn²⁺is relatively easy to dope in CsPbCl₃ nanocrystals,the proportion of manganese salts in the synthesis process is very high（MnCl₂/PbCl₂=1-10）,due to cost considerations,it has certain limitations in industrial applications.On the other hand,although the properties of CsPbCl₃ are not ideal compared with CsPbBr₃,such as low fluorescence quantum yield and high band gap of visible light absorption,it is difficult to dope Mn²⁺ions in CsPbBr₃ NCs by the same hot-injection method.Therefore,the establishment of a new low-cost,high-quality manganese-doped lead cesium perovskite nanocrystals is particularly important in future applications.In the second chapter,we propose a new"seeds method"doping methond for controllable synthesis of Mn:CsPbCl₃ nanocrystals,which can be synthesized controllably under low manganese salts with a very low feed ratio of MnCl₂,which is only 1%of the relevant literature.The effect of doping concentration on optical properties was studied.The results show that with the increase of MnCl₂ dosage in the system,the content of Mn²⁺in CsPbCl₃ nanocrystalline lattice increases,and the doping emission intensity increases first and then decreases,and the maximum value is reached when the feed ratio of Mn²⁺is 0.2%.In addition,the effect of reaction temperature on optical properties was also studied.The results show that with the increase of reaction temperature,the absorption peak of Mn:CsPbCl₃ nanocrystals gradually red shifts,and the host emission peak is adjustable in the range of 370-410nm.In order to further broaden the fluorescence emission range of Mn:CsPbCl₃nanocrystals,the host emission range of Mn:CsPbCl₃ nanocrystals was adjusted from405-470 nm by introducing PbBr₂ solution into the solution of Mn:CsPbCl₃nanocrystals by anion exchange method.In the third chapter,we synthesized Mn:CsPbBr₃ nanocrystals by"seeds method".The effects of ligands and lead salts on the reaction system were studied.The results show that oleic acid and oleamine ligands do not hinder the formation of Mn:CsPbBr₃nanocrystals,but are not conducive to the synthesis of pure phase nanocrystals.The existence of lead salts is not conducive to the formation of Mn:CsPbBr₃ nanocrystals.In order to obtain high quality Mn:CsPbBr₃ nanocrystals,the effects of reaction temperature and doping concentration on the reaction system of Mn:CsPbBr₃nanocrystals were also studied.The experimental results show that the doping of Mn²⁺can be achieved at 20-210℃.The absorption peak gradually red shifts with the increase of reaction temperature.The host emission peak of Mn:CsPbBr₃ nanocrystals can be adjusted in the range of 445-496 nm.The effect of doping concentration on the reaction system was studied.The results showed that with the increase of the ratio of MnBr₂ and the increase of doping emission intensity,the maximum fluorescence quantum efficiency of Mn:CsPbBr₃ NCs was obtained when the ratio of MnBr₂ was30%.At this time,the doping amount of Mn²⁺was 36.5%.