Research On Optical Properties Of Perovskite And Oil Phase Cadmium Telluride Quantum Dots

In recent decades,compared with traditional organic luminescent materials and solid phosphors,semiconductor quantum dots（QDs）have attracted increasing attentions due to their characteristics of size-dependent photoluminescence（PL）,large light absorption coefficient,excellent photothermal stability,simple solution processing.Therefore,thoroughly investigation on the QDs synthesis is significant for their technological development in the fields of light-emitting diodes（LED）,photovoltaic cells（PV）,and biomarkers.Based on these investigations,this paper has conducted a series of studies on the high-quality synthesis of all-inorganic perovskite（CsPbX₃,X=Cl,Br,I）,doped perovskite(CsPbC13:Mn²⁺),and cadmium telluride（CdTe）QDs in the organic phase from basic optical properties,surface chemistry to nucleation-growth kinetics.1.Cubic phase CsPbX₃ is an excellent candidate for photoelectric applications.In this section,we synthesized a series of CsPbX₃ QDs at room temperature by studying the intrinsic relevance between reaction solvent and nucleation-growth processes.Experiments show that the full width at half-maximum（FWHM）and the PL can be tuning via varying polarity of the reaction solvent.One of the most outstanding consequences is the synthesis of cubic phase CsPbI3 QDs at room temperature for the first time.Another breathtaking case is the first realization of ultra-small sized CsPbCI3 QDs with PL at 385 nm.In addition,in our scheme,we reduced the ligands loss of CsPbX₃ QDs and avoid the irreversible non-fluorescent phase transitions by eliminations of bad reaction solvents（such as ODE,DMSO,DMF）.The synthesized CsPbX₃ QDs exhibits 100%PL QY and long-term stability under moisture conditions.Further NMR characterizations showed that all ligands remained completely inactive states on defects sites,regardless of the initial paired X-type or degenerately hybrid L-X type ligands.Our synthesis scheme will promote photoelectric application of CsPbX₃ QDs.2.It is significant to synthesis CdTe QDs in organic phases at mild temperatures without utilization of explosive reagents such as trioctylphosphine-tellurium（TOPTe）.In this section,we have synthesized CdTe QDs via utilizing X-type ligand as initiator at low temperature.It was found that the initiator firstly induced the formation of CdTe magic size cluster（MSC1）,then induced generated new critical sized MSC₂,and finally converted MSC₂ to CdTe QDs.The experimental results show that the injection rate and concentration of initiator have a significant effect on the nucleation growth rate and morphology.The characterizations of XPS,Ramna and NMR indicated that the CdTe surface was coordinated by oleylamine,thioalcohol and initiator.The temperature-varying spectra and temperature-varying fluorescence lifetime show that CdTe QDs have defects derived from shallow level and deep level,respectively.Traditional passivation treatments such as chloride cannot completely inhibit second typed defect.This synthesis method will open a new entrance for applications of CdTe QDs in other optoelectronic fields.3.Simplifying synthesis,improving the stability,and improving PL QY of the CsPbCl₃:Mn²⁺QDs are the important preconditions for their optoelectronic applications.In this section,we developed a method to self-assemble CsPbCl₃:Mn²⁺QDs at room temperature.Our synthesis protocol controls the nucleation-growth kinetics through aryl chloride（third-party initiator）.The characteristic PL and PL intensity of Mn²⁺can be tuning by varying the ratio of Mn²⁺/Pb²⁺ concentration in the initial reaction solution or changing the injection rate of the initiator.The energy transfer efficiency between the CsPbCl₃ matrix and the Mn²⁺with aryl phosphorus chloride as the initiator is close to 100%.Our synthesis method will promote new applications of the CsPbCl₃:Mn²⁺QDs in other fields such as solar battery.