Quantum Dots Based Composites For Holographic Three-dimensional Display Application

Three dimensional display is regarded as a promising technique which can improve thevisual perception. Other than commercialized3D movie and TV using stereo parallaxtechnique, holographic3D display contains optical information of light amplitude andphase position which can produce visual effects identical to real scene. In holographic3Ddisplay systems, display medium is the key component in determining the quality ofreconstructed image.Up to today, many different materials including organic dyes, gases and rare-earth dopedcrystals have been studied as possible display medium candidates for3D displayapplications. However, these materials hardly fit in the requirements of3D imagevisualization. Gaseous materials suitable for holographic3D displays are toxic and need tobe kept in a chamber at high pressure. Rare-earth materials have many disadvantages likelow upconversion efficiency, processing difficulty and high cost to produce large crystals.The poor stability and photoluminescence quenching of organic dyes limit their applicationin holographic3D display. Hence, the challenge lies in3D display mediums wasdeveloping new display materials to meet the demands of holographic display.In this work, quantum dots based composites were designed and prepared as displaymediums in holographic3D display system. Besides, the properties of composites havebeen characterized by applying UV absorption, fluorescence spectra and their performancein computer-generated holographic display was also determined. The main achievementsare listed as follows.(1) PVA hydrogel embedded with quantum dots. Highly luminescent CdxZn1-xTe andZnSe/ZnS quantum dots with color tunable emissions in the visible region were controlledsynthesized through microwave-assisted method. These quantum dots were successfullyincorporated into PVA hydrogel at high temperature to obtain high transparent andfluorescent composites with healable features.3D images with high efficiency and goodclarity can be well reconstructed inside composites when they were placed in holographicdisplay system. The peak-signal-to-noise ratio value of image reached10.94, indicating thepotential applications for holographic display.(2) Double network hydrogel embedded with quantum dots. Double network hydrogelwith enhanced mechanical strength were synthesized by adjusting the cross-linking agent,monomer concentration. Colloidal Quantum Dots were incorporated into double network hydrogels through a diffusion method and the mechanical strength of hydrogel can bemaintained after quantum dots doping. The image reconstructed by using DN hydrogelcomposites has a peak-signal-to-noise of28.48, demonstrating the high image qualitynearly identical to the real objects. In addition, the hydrogel could repeat swelling andshrinking without break its structure, benefiting for the reuse. Meanwhile, the compositeshave good mechanical strength like resistance to shear force or pressure, which provide thefree-standing characteristic.(3) Upconversion materials. Two upconversion materials were successfully synthesizedand their potential application as display medium in holography was also discussed. Firstly,NaYF4:Yb/Er nanocrystals were prepared by thermal decomposition method. Secondly, weexplored the triplet-triplet annihilation upconversion materials using CuInS2-DPA, whichconvert green light into blue emission.