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Fan Chen skal forsvare avhandlingen sin for graden philosophiae doctor (ph.d.) ved Universitetet i Sørøst-Norge.
Han har fulgt doktorgradsprogrammet anvendte mikro- og nanosystemer ved Fakultet for teknologi, naturvitenskap og maritime fag.
Alle interesserte er velkomne til å følge den digitale prøveforelesningen og disputasen.
Sammendrag
With the development of fourth generation solid-state light source technology, phosphor materials have received widespread attention due to their distinctive wavelength conversion characteristics. At present, solid-state light source white light diodes, which are constructed using conventional blue light-emitting diodes in conjunction with yellow phosphor materials, have emerged as the predominant light source in the domains of lighting and display technology. However, the absence of red spectral components in this light source results in diminished quality, rendering it inadequate to meet the growing demands for high-quality lighting.
Consequently, the incorporation of red spectral components into the light source spectrum has emerged as a viable strategy to enhance the overall quality of the light source. Inorganic compounds doped with trivalent europium are highly regarded by researchers owing to their pronounced red emission characteristics. Currently, several inherent limitations of red fluorescent materials employing trivalent europium as the luminescent center—including extended electron lifetimes, narrow excitation spectra, and low quenching temperatures—continue to restrict their photoluminescence performance. These drawbacks ultimately result in diminished electro-optical conversion efficiency in practical applications.
The aim of this PhD research is to optimize the photoluminescent performance of red phosphor materials with Eu3+ as the luminescent center, enhancing their competitiveness in applications within the fields of lighting and display. The main achievements are summarized in the following paragraphs.
In this work, a new method has been successfully developed to improve the photoluminescent performance of Eu3+ doped Y2(MoO4)3 red phosphor material through lattice ordering. Eu3+ doped Y2(MoO4)3 powder samples were subjected to high-temperature annealing to achieve large-scale ordered lattice arrangement, forming dense ceramic piece, thereby enhancing their photoluminescent performance. The main improvements include: the excitation peak has been broadened by more than two-fold; the absorption efficiency increased from 22% to 67%; the zero-quenching temperature has increased from 75 ℃ to 200 ℃; the electronic lifetime decreased from 0.716 milliseconds to 0.634 milliseconds.
In addition, a novel red phosphor material Eu3+ doped Y2(WxMo1-xO4)3 (x=0, 0.25, 0.50, 0.75, and 1.0) has been successfully synthesized, and the lattice structure the sample depending on the synthesis temperature and Mo/W ratio has been studied. The photoluminescent performance of samples with different lattice structures was evaluated. In addition, the measured thermal quenching temperature of the sample was found to be 200 ℃, indicating that this material is highly promising for use in harsh environments and can withstand high excitation power density.