Luminescent Materials And Their Opto-electronic Characteristics In Optically Written Display Based On Up-conversion

The optically written display based on up-conversion is an emerging display. Ainfrared diode laser is used as excitation source. The light from the diode is scannedonto a screen with three luminescent materials, and the materials radiate blue, greenand blue light. The display has a very good application prospect because of themerits such as high efficiency, full colour, high luminance, high resolution and longlife, especially the application of three dimensional displays.The up-conversion luminescent materials are required to have loose and smallparticles for high resolution displays. Their emission spectra should present narrowemission bands or multi-layer dielectric filters are designed to filter out the unwantedcolors to improve the chromaticity of images.The main results obtained are summarized as follows.1. Three primary luminescent materials were fabricated by the sprayingmicrowave combustion method. They are YF₃: Er,Yb as a red emitter, NaYF₄: Er,Yb as a green emitter, and KY₃F₁₀: Yb, Tm as a blue emitter. Their structuralcharacterization and grain size were mearured by XRD and TEM. The results are thesame by the two meansurement mehtods. The grain size are tens nm, which issuitable for high resolution display.2. The three materials' spectra were given when the diode lasers' pumping wavelength is 1064nm and 980nm. The the luminescent mechanism were analysed.The spectrum were obtained when the got when the 1064nm diode laser hasdifferent intensity. The laser power-dependent logarithmic graph of fluorescentintensity and its slope were given. The red emission in YF3: Er, Yb lies on themulti-phonon relaxation of ⁴S_3/2→⁴F_9/2 while the red emission in NaYF4: Er, Yb lieson the transition of ⁴I_13/2→⁴F_9/2.3. In order to filter out the unwanted colors for three primary luminescentmaterials, one multi-layer interference dielectric long-wavelength pass filter for redscreen, and two short-wavelength pass filters for green and blue screens weredesigned and fabricated on the luminescent screens, respectively. Thelong-wavelength pass filter's and short-wavelength pass filters' transmittance weremore than 98% for the wanted colors, the transmittance were less than 2% for theunwanted colors. The simulated angle-dependent transmittance of the filters waspresented. The filters have good characteristics within the whole wavelengthbandwidth and the incident angles of 0°～30°. The tolerance of the filters isreasonably large because filters' transmittance changes within 3% when the layersthickness and refractive index vary by±3% from the optimal designs. Theencompassed color triangle of the display with filters is larger than that withoutfilters, and images with more saturated colors are obtained.