Controlled Fabrications Of Organic Metal Halide Perovskite Quantum Dots And Study On Optical Properties

Organic metal halide perovskite quantum dots?QDs?,as emissive components,have been explored for applications in light-emitting diodes devices because of tunable emission spanning the whole visible range,narrowband emission and large ambipolar charge carrier mobilities.Reprecipitation method was adopted by many researchers due to its simpleness and versatility.However,there are concerns as to the formation of large particles during the reprecipitation step,leading to reduction of the yield of perovskite quantum dots.Therefore,it has become a very hot issue on how to synthesize pure perovskite quantum dots and to reveal the formation mechanism properly.In this dissertation,suitable synthetic components were chosen to investigate the preparation methods of perovskite quantum dots,formation mechanism and optical properties under the interaction of multicomponent solvent.At first,we obtained perovskite quantum dots and perovskite nanoparticles by two-step method and partly achieved the conversion from perovskite nanoparticles to QDs.The synthetic mechanism of perovskite QDs and optical properties have been well studied at the same time.Based on it,perovskite QDs with tunable emission wavelength were prepared by regulating the reaction conditions.We have made some important achievements which are as follows:?1?We chose lead bromide?PbBr₂?,a layered molecule,and methylamine bromide molecules?MABr?,which could formed the CH₃NH₃PbBr₃ QDs by two-steps method.In this process,we got two different Pb-containing intermediates,one is PbBr₂-DMF-OcAm quantum dot and the other is PbBr₂-DMF nanoparticle.And then we obtained different sized perovskite QDs?2.3 nm-5.4 nm?and nanoparticles?25-300 nm?with various dosage of oleic acid?OA?.The QDs were obtained with high photoluminescence quantum yields?34-71%?.And their emission wavelength can be tuned from 500 nm to 534 nm.During the synthesis process,the layered structure and the solvent effect play important roles in the formation of QDs,thus we put forward the possible reaction mechanism.?2?The perovskite QDs have a wide range of emission wavelengths.Based on the understanding of the formation mechanism of perovskite QDs and by selecting different conditions,we obtained CsPbBr₃,CH₃NH₃PbI₃ and CH₃NH₃PbI_xBr_3-x perovskite QDs with different emission wavelengths?494 nm-684 nm?,which lays a foundation for the extensive application of perovskite quantum dots in optoelectronic devices.Meanwhile,perovskite nanoplates were obtained by adjusting the dosage of surfactant,which extended the application fields of perovskite materials.