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In this study, we investigate the use of phosphor materials to enhance the efficiency of solar cells. A phosphor usually consists of a host material doped with rare-earth ions. This study aims to identify a suitable host and ions and, by empirical methods, optimise the phosphor for application in solar technology.

Radiation Dosimetry Phosphors provides an overview of the synthesis, properties and applications of materials used for radiation dosimetry and reviews the most appropriate phosphor materials for each radiation dosimetry technique. The book describes the available phosphors used commercially for their applications in the medical field for dose measurements. Although radiation dosimetry phosphors are commercially available, continuous efforts have been made by the worldwide research community to develop new materials or improve already existing materials used in different areas with low or high levels of radiation. Moreover, researchers are still working on developing dosimetric phosphors for OSL, ML, LL and RPL dosimetry. This book provides an overall view of the phosphors available, low cost synthesis methods, mechanisms involved, emerging trends and new challenges for the development of emerging materials for radiation dosimetry. It is suitable for those working in academia and R&D laboratories in the discipline of materials science and engineering, along with practitioners working in radiation and dosimetry.

The efficient blue luminescence of Eu2+ doped BaMgAl10O17 is well-known to be severely degraded by prolonged irradiation with vacuum-ultraviolet light. The degradation process at the atomic level is however not fully understood. In this work we employed X-rays as an equivalent but accelerated cause of degradation, as an excitation source of luminescence and as an element-selective probe of both dopants and host-lattice chemical species. The X-ray absorption near edge structure (XANES) recorded in high energy resolution mode reveals that the structural properties of the host lattice are preserved during irradiation, while Eu2+ is rapidly oxidized. The correlation between Eu oxidation as derived from XANES and the decrease of blue luminescence is however not linear and a significant fraction of Eu2+ survives degradation, implying additional mechanisms for the quenching of the luminescence. Defects created during the photogeneration may reduce the ability of the remaining Eu2+ to receive or to radiatively release energy. A kinetic Monte Carlo simulation confirms that defects in the vicinity of a photogenerated Eu3+ can act as killer centers for the remaining Eu2+ and explain the observed accelerated quenching of the blue luminescence. The present approach, which takes full advantage of the different interactions of X-ray radiation with impurity doped luminescent materials, can easily be transferred to reveal degradation pathways in other phosphors.

Laser excitation and x-ray spectroscopy are combined to settle a long-standing question in persistent luminescence. A reversible electron transfer is demonstrated, controlled by light and showing the same kinetics as the persistent luminescence. Exposure to violet light induces charging by oxidation of the excited Eu2+ while Dy3+ is simultaneously reduced. Oppositely, detrapping of Dy2+ occurs at ambient temperature or by infrared illumination, yielding afterglow or optically stimulated luminescence, respectively.

Eu-doped BaMgAl10O17 (BAM) is an excellent inorganic phosphor. Its luminescence efficiency is however severely degraded during prolonged vacuum-ultraviolet (VUV) excitation. Furthermore, the degradation process at the atomic level is not yet fully understood. To shed light on this process, we simultaneously employed X-rays as an equivalent but accelerated source of damage, as an excitation source of luminescence and as an element-selective probe of both dopants and host-lattice chemical species. We investigated commercial samples of Eu doped and Mn, Eu co-doped BAM. We measured High-Energy Resolution Fluorescence Detected (HERFD)-XANES at Eu and Ba L3-edges and at Mn K-edge. The X-ray induced radio-luminescence (RL) and the HERFD-XANES spectra were simultaneously acquired while progressive damage was induced. The evolution of the RL spectra confirms that the degradation induced by X-rays and by VUV irradiation are equivalent. The HERFD-XANES reveals that Ba and Mn are stable under the X-ray beam, while Eu2+ undergoes a rapid oxidation to Eu3+. We found that the correlation between Eu oxidation and RL intensity decay is non-linear and that a significant fraction of Eu2+ resists to irradiation, implying that an additional mechanism is responsible for the quenching of the remaining Eu2+. A kinetic Monte Carlo simulation indicates that the creation of defects acting as killer centers in the vicinity of a photo-oxidized Eu3+ can reproduce the dynamics observed on RL and Eu oxidation. By simultaneously degrading and probing Eu-doped BAM we found [1] that the degradation process is due to oxidation of the luminescence impurities combined with the formation of killer centers that quench the luminescence of the remaining Eu2+.

The efficient blue luminescence of Eu2+ doped BaMgAl10O17 is well-known to be severely degraded by prolonged irradiation with vacuum-ultraviolet light. The degradation process at the atomic level is however not fully understood. In this work we employed X-rays as an equivalent but accelerated cause of degradation, as an excitation source of luminescence and as an element-selective probe of both dopants and host-lattice chemical species. The X-ray absorption near edge structure (XANES) recorded in high energy resolution mode reveals that the structural properties of the host lattice are preserved during irradiation, while Eu2+ is rapidly oxidized. The correlation between Eu oxidation as derived from XANES and the decrease of blue luminescence is however not linear and a significant fraction of Eu2+ survives degradation, implying additional mechanisms for the quenching of the luminescence. Defects created during the photogeneration may reduce the ability of the remaining Eu2+ to receive or to radiatively release energy. A kinetic Monte Carlo simulation confirms that defects in the vicinity of a photogenerated Eu3+ can act as killer centers for the remaining Eu2+ and explain the observed accelerated quenching of the blue luminescence. The present approach, which takes full advantage of the different interactions of X-ray radiation with impurity doped luminescent materials, can easily be transferred to reveal degradation pathways in other phosphors.

Low doses of ultraviolet B (UV-B) light have significant effects on plant morphology [1]. In Arabidopsis, many UV-B induced morphological modifications have been ascribed to the UV-B specific receptor UV resistance locus 8 (UVR8). Recent findings in etiolated Arabidopsis seedlings indicate that UVR8 regulated signaling can induce phototropin independent directional bending towards UV-B light [2]. Here, we study the relative contribution of each of these pathways in UV-B regulated phototropism through kinetic analysis of seedlings. The role of phototropins is favored under reduced light conditions and the higher UVR8 response in the UV-B hypersensitive rup1rup2 mutants is interfering with the fast phototropin-regulated phototropic response. Our data suggest that phototropins are the primary receptors for UV-B induced phototropism in etiolated Arabidopsis seedlings, and the RUP-mediated negative feedback pathway prevents UVR8-mediated signaling to affect the phototropin-dependent response. In conclusion, phototropins are the most important receptors for UV-B induced phototropism in etiolated seedlings, and a RUP-mediated negative feedback pathway prevents UVR8 signaling to interfere with the phototropin dependent response.

Phosphor-converted white light-emitting diodes (pcLEDs) are now commonly used in general lighting and display backlighting. For the latter application, red and green phosphors with saturated colours are preferred to reduce filtering losses. In this paper we report on our studies on green-emitting thiogallate phosphors (ZnGa2S4:Eu and SrGa2S4:Eu) with narrow emission bands.