| Spectral down-conversion(DC) materials can convert one high energy UV/visible photon which can not be effectively utilized by the c-Si solar cells to two or more near-infrared(NIR) photons around operating wavelength of the c-Si solar cells. It is of value to improve the utilization of solar energy by means of quantum cutting. To enhance the conversion efficiency of solar cells, near-infrared QC can be realized by using coupled rare earth(RE) ions due to their unique energy level structures and high quantum efficiency. However, the most studied DC materials can not be used for c-Si solar cells due to the low quantum yield from UV/ Visible to NIR. Chalcogenide glasses have been extensively studied for several decades because of their optical transmission from the visible up to the far infrared region, covering the widely used atmospheric IR windows of 3-5 and 8-12 μm. Moreover, chalcogenide glasses have been demonstrated to be a good candidate for hosting RE ions to obtain high ET efficiency and QY because of their low phonon energy(~350 cm-1).In chapter I, the concept of glasses and RE ions’ luminescence, the main characteristics of preparation methods of the glasses doped with RE ions were summarized. The research progresses of RE ions doped glasses were introduced. Also the significance and main content of the research were summed up.In chapter II, the methods of measurement and preparation of these glasses were presented.In chapter III, visible to near-infrared downconversion in Tm3+/ Yb3+ co-doped chalcohalide classes for solar spectra converter were studied. Absorption spectra, emission spectra, excitation spectra, and decay measurements were performed to prove the occurrence of cooperative energy transfer from the 1G4 level of Tm3+ to two Yb3+ ions. The results indicate the potential prospect towards the development of Tm3+/ Yb3+ co-doped chalcohalide glasses in realizing high efficiency silicon-based solar cells by downconversion of the ultraviolet part of the solar spectrum to 980-1025 nm infrared emission.In chapter IV, Pr3+-Yb3+ codoped chalcohalide glasses were investigated as a downconversion layer candidate to enhance silicon solar cell efficiency. The glasses were prepared with the following composition(in mol. %): 25 Ge S2-35Ga2S3-40 Cs Cl: 0.2Pr2S3-x Yb2S3(x=0, 0.1, 0.2, 0.3, 0.4, 0.6) by vacuumed melting-quenching method in a silica glass ampoule. Absorption spectra, emission spectra, excitation spectra, and decay measurements were performed, it is determined that one visible photon has been cut to two near-IR photons during the energy transfer process. The maximum value of quantum efficiency measured by the integrated sphere is 10.8 %. Although this efficiency is still low, but this result will open a new route to realize efficient spectral modification of solar spectrumIn chapter V, effect of Ag addition on the third-order nonlinearity and physicochemical property of chalcohalide glass were mainly studied. Variety contents of Ag2S(0~10 mol. %) were introduced into 70 Ge S2-20In2S3-10 Cs I glass. The physicochemical properties, such as glass transition temperature, density, refractive index, transmittance, hardness as well as third-order nonlinearity are investigated with the increasing Ag2 S contents. The Ag-containing glass, which exhibited good thermal stability, excellent infrared transparency and ultrafast nonlinear optical properties, can be find applications for the IR window material or ultrafast infrared optics.In chapter VI, Crystallization behavior of 70 Ge S2-20In2S3-10 Cs I chalcohalide glass with silver addition was mainly studied. The crystallization behavior of the 70 Ge S2-20In2S3-10 Cs I glass introduced with 2 mol. % Ag2 S system has been studied under non-isothermal condition. By heat treatment, the mechanical property was improved. Based on the DSC, XRD, and SEM, the crystallization mechanism is elucidated in detail.Finally, the main conclusions of this research were summarized, and some improvements which should be done in the future work are also discussed. |
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