| The near infrared luminescence is widely used in the lasers, optical fiber communications, conversion of solar spectrum, and biological fluorescent labeling, etc. Due to the rich energy-level structure of earth ions, the various near infrared luminescence can be obtained by earth ions. Therefore, the new generation of near infrared luminescent materials have attracted many researchers' attention. It is well know that the 4f inner shell transitions of earth ions are parity forbidden transitions. Hence, the low excitation efficiency of 4f inner shell transitions will result in the low luminous efficiency. In order to increase the excitation efficiency, sensitization might be an effective pathway to increase the earth ions absorption and therefore make luminescence generation more efficiently. The possibility to improve the earth ions absorption through sensitization have been studied with various sensitizers including transition- metal ions, semiconductors and some earth ions, etc.The content of this paper includes 5 parts. Chapter 1 briefly introduces the properties of near infrared luminescence and the applications of earth ions in the luminescent materials area. In addition, the principle of sensitized luminescence was explained. C hapter 2, the theoretical basis of luminous of rare earth ions and the energy transfer theory of sensitized luminescence were explained.In chapter 3, a great sensitization of the Mn4+ to Er3+ in the Ca14Zn6Al10O35 matrix was found. The Mn4+ exhibits broadband absorption(UV and visible range) in Ca14Zn6Al10O35, which effectively broaden the excitation spectrum of Er3+ near infrared luminescence. The excitation and emission spectra of Mn4+ and Er3+ and the energy transfer process from Mn4+ to Er3+ are discussed in detail.In chapter 4, based on the study of chapter 3, a great sensitization of the Mn4+ to Nd3+/Yb3+ in the Ca14Zn6Al10O35 matrix also was found. The Mn4+, Nd3+/Yb3+ codoped Ca14Zn6Al10O35 luminescent materials convert the absorbed UV-visible light into the infrared light via the sensitization of Nd3+/Yb3+ near infrared emission by Mn4+. Due to the Si-based solar cell works most efficiently under irradiation of the infrared light(wavelengths of around 1000 nm), hence the phosphors can possibly be used as spectral conversion materials to enhance the efficiency of Si-based solar cel.In chapter 5, the g-C3N4: Yb3+ composite material is synthesized. We found the Yb3+ can compounded on the g-C3N4 and the composite material can convert the absorbed blue-violet light into the near infrared luminescence of Yb3+ via the sensitization of Yb3+ emission by g-C3N4. |
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