The Investigations On The Colour Modification Of Upconversion Phosphate Inverse Opal Photonic Crystal

Rare earth ion doped upconversion luminescent materials have great potential for applications in the field of infrared detection, cooling, laser device, three-dimensional display. Especially for three-dimensional upconversion display, the regulation of three primary colors which are red, green, and blue is particularly important. The upconversion luminescence in the three primary colors on the display has its unique advantages, such as color purity. Current method for color modification of upconversion luminescence is doping multiple rare earth ions, changing density of ions or power of pump excitation power. The main drawback of all the methods is uncontrollable light-emitting process. Photonic crystal which is known as a new photoelectric materials, can take advantage of its unique photonic bandgap properties, modulating upconversion luminescence by suppression effect of band gap or enhancement effect of band edge for the purpose of color adjustment.Phosphate materials have already been widely applied in the field of optoelectronic materials. Good stability and easy preparation make it a good choice as a matrix of upconversion luminescence material. This study investigated the phosphate inverse opals with a variety of photonic bandgap, observed upconversion luminescence properties of a variety of rare earth ions under excitation of a980nm laser, and strive to modulate the behavior of upconversion luminescence for achieving the purpose of color adjustment.There is an overview of the upconversion luminescence materials at the beginning of this script, including the mechanism, influencing factors, as well as applications. Then some major problems of upconversion color modification were pointed out, and the concept of photonic crystals was introduced. At the meantime, the purpose and significance of the use of photonic crystal in regulating upconversion luminescence were described. The experimental section describes the preparation methods of opal and inverse opal. Meanwhile, the examining method for the upconversion luminescent properties of inverse opal was described. In the part of experimental results, the upconversion luminescence properties of Tb3+/Yb3+co-doped phosphate inverse opals was investigated firstly. The properties of opal templates were investigated, the microstructure of inverse opal was observed by metallurgical microscope and scanning electron microscope, and the band gap of552nm was found through the transmission spectrum. In the end, the inhibitory effect of photonic band gap on upconversion luminescence was observed under excitation of980nm laser, so the color modulation work of upconversion luminescence was successful.After that, upconversion color modification of Tm3+, Er3+single-doped YbPO4inverse opal was investigated respectively. On the basis of preparation of two set of inverse opal, the microscopic structure, photonic bandgap, and upconversion luminescence properties were characterized by detection method. Band gap at480nm and550nm were found in YbPO4:Tm3+inverse opal. Band gap at480nm inhibited upconversion emission peak corresponding to1G4→3H6transition of Tm3+while Band gap at550nm enhanced it. In addition, by changing the laser power, mechanism of upconversion luminescence was studied. Transition1G4→3H6of Tm3+in YbPO4:Tm3+inverse opal was three-photon absorption process, while the transition3F3,2→3H6is two-photon absorption process. In the other hand, bandgap at475nm,548nm and680nm were found in YbPO4:Er3+inverse opal. Band gaps at475nm and548nm, enhanced and suppressed the upconversion peaks correspond to transition2H11/2→4I15/2and4S3/2→4I15/2of Er3+respectively; the680nm band-gap suppressed the upconversion peak corresponding to transition4F9/2→4I15/2of Er3+. At last, the CIE chromaticity coordinates of inverse opals were calculated out, and the purpose of three primary color modulation was achieved while upconversion luminescence was regulated.Upconversion color modification of Ca5(PO4)3F:Tb3+/Yb3+inverse opal were investigated later.489nm and543nm photonic bandgap were found in inverse opals. It could be observed that under the excitation of980nm laser,5D4→7F6and5D4→7F5transition of Tb3+were suppressed the band gap effect. And the calculation of CIE chromaticity coordinates of all samples proved the upconversion behavior and color was tunable. In addition, through the variation of excitation power, upconversion mechanism of all the emission peaks of Tb3+in Ca5(PO4)3F:Tb3+/Yb3+was second order processes.At the end, all the work was summarized and current problems as well as future plan were pointed out.