Low toxicity metal halide semiconductors for optoelectronics and thermoelectrics

Résumé

In order to fight against climate change and support renewable and non-polluting energies, the main objective of this thesis is the search and study of new materials with potential application in three main research areas: photovoltaics, thermoelectrics and light-emitting diodes (LEDs). Since many of the materials used in these areas contain toxic and environmentally harmful components, the materials developed in this thesis also have low toxicity and can be prepared by more sustainable and environmentally friendly synthesis and deposition methods. Specifically, two synthesis methods were used: dry mechanosynthesis by ball milling and single-source vacuum deposition. These methods are preferred because they are cleaner and generate less waste than traditional synthesis methods such as solution-based chemical synthesis. Chapter 3 presents two families of inorganic copper halides, which were shown to have potential for use in LEDs. These copper compounds emit green or blue light, depending on the halide used. One of the compounds, Cs3Cu2I5, proved to be particularly interesting due to its high blue efficiency. Chapter 4 focuses on a silver-bismuth compound, commonly known as double perovskite. In particular, the double perovskite Cs2AgBiBr6 was modified to reduce its bandgap and thus improve its applicability in photovoltaics. Different dopants were tested and it was shown that tin-doped thin films achieved the highest bandgap reduction. Finally, in Chapter 5, three different species in the Cs-Sn-I system were studied for thermoelectric applications. It was shown that the beta phase CsSnI3 achieved higher efficiency and remained stable under inert conditions for more than one week. Thus, the results of this thesis have important implications for the optoelectronics and thermoelectric industries, as well as demonstrating the importance of using more sustainable and environmentally friendly synthesis and deposition methods for the reduction of environmental impact in these areas.