Development of Phosphors for Light Conversion and Thermography in Solar Panels
Entwicklung von Leuchtstoffen zur Lichtumwandlung und Thermografie in Solarmodulen
Creators: name: Ali, Amjad
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2024
Subjects: Thermography, Laser induced fluorescence thermography, Phosphors, Luminescent materials, Phosphor thermography, Light conversion

description: The most significant parameter that impacts practically all industrial processes in many ways is temperature. Novel methods of temperature measurement, like phosphor thermometry, are very useful in many situations where conventional techniques have some limitations. Lack of measurement in two-dimensional (2D) space is a significant drawback of conventional techniques. Phosphor thermography has many advantages in 2D measurement in terms of resolution, accuracy, and cost in comparison with competing techniques like infra-red, thermal paints, and liquid crystals. The phosphor thermography method is based on the photoluminescence characteristics of a phosphor material that is affected by temperature in most phosphors. The search for a suitable phosphor material which can survive harsh measurement conditions with suitable optical characteristics is of prime importance. The focus of this work is to investigate suitable phosphor materials and develop a cost-effective lifetime-based technique. At the start of the thesis, the motivation behind this work is given. In chapter 2, the reader is provided with the knowledge of conventional temperature measurement techniques and commonly employed 2D techniques other than phosphor thermography, along with their pros and cons. Chapter 3 starts with the development history of phosphors, and then the basic theory behind luminescence is discussed. Radiative and non-radiative processes occurring during absorption, emission and energy transfer are also discussed. Energy levels in transition metals and rare earth elements, which will be used often in the luminescence Radiography, are also given. Chapter 4 describes the different methods of phosphor thermography along with their advantages and disadvantages. It also describes the experimental factors that may contribute to the errors in the measurement. Manganese-doped magnesium germanate phosphor is the most frequently used phosphor for thermography applications. However, there are various compounds possible with different stoichiometries of magnesium and germanium oxides. Fluoride ions may also replace some oxide ions in magnesium germanate and increase the emission many times. In my first paper of the appendix, the synthesis and characterization of different compositions of magnesium germanate and fluoro-germanate phosphors are discussed. A strikingly unique observation was made during the synthesis of magnesium fluoro-germanate phosphor that the moisture content during the synthesis can severely deteriorate the photoluminescence emission. This phenomenon is investigated in the second paper of the appendix. In the third paper attached, a new method is introduced for the determination of lifetime in 2D space using a conventional low-speed scientific grade camera. In contrast to the well-known present methods, the technique relies on capturing multiple images in multiples decay curves with progressively shifted integration time window after excitation. The obtained results indicate a relatively low standard deviation in 2D thermography in a wide temperature range.