Investigation Of The Optical Properties Of Doped Perovskite Nanocrystals And Hybrid Nanomaterials

Recently,all-inorganic perovskite nanocrystals?PNCs?become the contemporary star materials due to their flexible crystal configuration and unique physicochemical properties.It has excellent optical and electrical properties,such as high photoluminescence quantum yield?QY?,narrow and tunable fluorescence emission peaks,wide color gamut range and fast carrier mobility,which has been widely used in light-emitting diodes?LED?,solar cells and photodetection.Nevertheless,in the course of their development,there still remain some problems that we cannot ignore and need to solve urgently.The main issues are the low emission yield of blue-violet light based on CsPbCl₃ PNCs,the poor stability of PNCs themselves and under environmental conditions as well as the limitations of the optical absorption range only in the visible region.At present,hetero-ion doping and construction of hybrid nanomaterials have been proved to be the effective methods to improve the optical properties of fluorescent nanomaterials.In this dissertation,we will improve the fluorescence properties of PNCs from both the emission and excitation performances.The blue-violet emission QY of CsPbCl₃ PNCs was effectively improved by doping of hetero-ion,and the UV illumination stability was also enhanced.Moreover,the hybrid nanomaterials were constructed to achieve fluorescence emission of near-infrared-triggered PNCs by and broaden the effective light absorption range of PNCs.The results achieved as follows:?1?F^-ion-doped CsPbCl₃ PNCs and F^-/La³⁺ions co-doped CsPbCl₃ PNCs were successfully synthesized by thermal injection method.Introduction of F^-ions resulted in an enhanced photoluminescence QY from the initial 3.4%of CsPbCl₃ PNCs to 9.3%of CsPb(Cl_0.7F_0.3)₃ PNCs and further increased to 36.5%when introduction La³⁺ions.The improved photoluminescence performance was related to the decreased nonradiative recombination pathways and increased radiative recombination rate of PNCs.Moreover,we used CsPb(Cl_0.7F_0.3)₃:La³⁺PNCs as inks for nano-printing,showing its potential applications in anti-counterfeiting.?2?By using thermal injection method,we systematically investigated the effects of doping Co²⁺ions on the morphology,structure and fluorescence properties of CsPbCl₃ PNCs.The results shown that the CsPbCl₃ PNCs morphology and crystal structure could be effectively regulated by adjusting the doping concentration and synthesis temperature of Co²⁺ions.Meanwhile,the introducing of Co²⁺ions could reduce the density of defect states and increase the radiative recombination rate of CsPbCl₃ PNCs,thus resulting in an enhanced fluorescence QY from the 4.2%of CsPbCl₃ PNCs to 83.3%of CsPbCl₃:Co²⁺PNCs.?3?NaYF₄:Yb,Tm@SiO₂-CsPbBr₃ hybrid nanomaterials were successfully designed and prepared.By using of up-conversion effect,the fluorescence emission of PNCs triggered by near-infrared was realized and the effective light absorption range of PNCs was broadend.Through adjusting the thickness of SiO₂ shell between up-conversion nanoparticles and PNCs,we studied the fluorescence emission properties and the luminescence mechanism of PNCs in the hybrid nanoparticles in detail.It was found that only when the thickness of the SiO₂ shell was relatively thin,the effective fluorescence emission of the PNCs was achieved by nonradiative resonance energy transfer process between the NaYF₄:Yb,Tm nanoparticles and the PNCs.Otherwise,the fluorescence emission of the PNCs tended towards the re-absorption process of the emitting photons.