Study Of Optical Manipulation And Photoluminescence Enhancement Based On Planar Thin-film Stacks

Light is an important information carrier,which plays an important role in human understanding and transforming the world.With the development of science,people gradually realize that the essence of light is electromagnetic waves.It has always been the dream of human beings to realize the manipulation of electromagnetic waves.Artificial electromagnetic material is an artificial structural material with special electromagnetic properties,which is formed by arranging the artificial unit structure in a specific way.One-dimensional planar thin-film stacks is an important branch in the fields of metamaterials,which has the characteristics of simple structure,easy preparation and compatibility with modern semiconductor technology,so it has attracted more and more attention in recent years.All-inorganic cesium-lead halide perovskite quantum dots have shown very attractive application prospects in solar cells,light-emitting diodes,photodetectors and other fields because of their excellent optoelectronic properties,such as high light absorption coefficient,flexible wavelength and high quantum yield.The purpose of this thesis is to realize the artificially manipulating of electromagnetic parameters through theoretical design and experimental preparation of planar thin-film stacks,and to study the physical process and mechanism of photoluminescence（PL）enhancement of perovskite quantum dots（QDs）.The main research contents and innovations are as follows:1.We proposed and demonstrated that the light emission of Cs Pb Br₃ perovskite QDs can be remarkably enhanced by using metallic thin films.PL intensity as a function of both the thickness of the metallic thin film and the dielectric spacer were performed.An impressive 11-fold maximal PL enhancement factor was obtained with respect to the emission of perovskite QDs on the bare dielectric substrate when the thickness of Ag=60nm,Si O₂=10 nm.The field enhancement effect and time-averaged energy dissipation density were revealed by numerical simulation of field distribution,and the dynamic process of PL intensity attenuation was analyzed from the results of time-resolved PL spectra.The basic physics behind the large enhancement involves two aspects:first,the absorption of QDs at the excitation wavelength is greatly enhanced due to the strong optical asymmetric FP-like thin film interference effect.Second,the surface plasmon increases the radiation rate and quantum efficiency of QDs at the emission wavelength.This research can open up new avenues to expand the practical applications of high-performance perovskites optoelectronic device,such as light emitting diodes,biological sensors,and plasmonic lasers.2.We proposed and prepared experimentally a novel ultra-thin,large-area and resonant tunable planar bilayer media,which was composed of deep-subwavelength thickness and high absorptive Cu O thin films and Au substrate.Experimental results showed that reflectance spectra of Cu O/Au bilayer can be sensitively adjusted by changing the thickness of Cu O film.Compared with the bare quartz based reference sample,PL enhancement factor of Quantum dots/Cu O/Au trilayer can be achieved by up to 7 times.The PL enhancement factor decreases with the increase of the thickness of copper oxide thin films.Theoretical analysis showed that PL enhancement effect is related to the high efficient absorption caused by Fabry-Perot thin film interference and the accelerated spontaneous emission rate resulted from local field enhancement.The proposed optical coating scheme,which is composed of metal and high loss media,has good development potential in many application fields,such as metal structure color,photodetection,energy collection,radiation cooling and so on.3.We proposed and proved experimentally that PL enhancement of Cs Pb Br₃QDs can be realized by using trilayer MIM and five-layer MIMIM plasmonic nanocavity.Firstly,the structural parameters were optimized by transfer matrix method,and the nanocavity samples were prepared experimentally.PL measurements showed that the PL enhancement effect of the trilayer MIM resonant cavity at the excitation wavelength of 405 nm and the emission wavelength of 520 nm QDs was about 6 to 7times.In MIMIM dual-wavelength system,a significant 12-fold PL enhancement was obtained due to combined action of absorption enhancement and coupling emission effect.The distribution characteristics of electromagnetic field and absorption energy dissipation are given by numerical simulation,and the field enhancement mechanism of PL enhancement was clarified.The decay kinetics of luminescence of the composite system was analyzed by time-resolved PL technique.The aforementioned solution of controlling light emission by plasmonic cavity has established a general platform for promoting engineering applications in the field of optics,and has high tunability and a wide range of applications.4.We theoretically designed and experimentally explored the use of multilayer Tamm plasmon optical microcavity to control the spontaneous emission of Cs Pb Br₃quantum dots.Firstly,the basic structure and material composition of optical Tamm plasmon were designed and optimized theoretically by transfer matrix method.Then,samples were prepared in experiment according to the optimized parameters.SEM cross section and optical reflection spectrum showed that experimental results are in good agreement with theoretical predictions.Finally,PL enhancement of the microcavity QDs system at 530 nm was about 5 times higher than the reference sample.Numerical simulation results showed that the electric and magnetic field in the TPP optical microcavity were asymmetrically distributed,and the absorbed energy was mainly dissipated in the top metal and quantum dots of the microcavity.Although the preliminary PL enhancement effect has been achieved,there is still room for further optimization in the experiment,which lays a foundation for expanding a variety of optoelectronic applications of Tamm and other plasmon microcavities.