Chalcogenides - ebook

INTRODUCTION

Last decades brought a development in research of new materials, especially in photovoltaics. They are the most often substances not occurring under natural conditions and they can be obtained only with the use of new preparation methods. These are, first of all, binary compounds, such as fluorides, sulfides, selenides, tellurides, nitrides, arsenides, phosphides, antimonides, silicides, and also complex ternary compounds – products of reactions of the binary compounds mentioned, such as fluoro- or thiosalts or complex selenides. The latter are capable of forming many compounds with various elements of the periodic system, e.g. aluminium MAlS₂, gallium MGaS₂, silicon M₂SiS₃, M₄SiS₄, arsenic M₃AsS₄ etc. (where M is a metal of the 1^(st) group in the periodic system).

A poor side of inorganic chemistry may result from the lack of general theory enabling a uniform presentation of structures, properties, and preparation methods of the enormous amount of compounds hitherto obtained. Such a state was also a limiting factor in theoretical forecasting. The new version of the morphological classification, used in this monograph, has become possible, at least in part, to present instead of encyclopaedic review of chemical compounds a balanced, coherent and comprehensive knowledge of the chemistry of chalcogenides.

In the recent decade, sulfides, selenides and tellurides probably have become the most fashionable group of simple chemical compounds, mainly owing to several compounds, such as zinc and cadmium sulfides, zinc and cadmium selenides or zinc and cadmium tellurides, and more complex ternary CuSnS₂, and quaternary CuIn_(x)Ga_(1-x)Se₂ (CIGS) or Cu₂ZnSnS₄ (CZTS – kesterite) etc. – all referred to as compounds of technological future in optoelectronics and photovoltaics. The nanopowders of CdSe are used as inorganic part of composites in new light-emitting diodes. The thin layers of CdTe can replace thick silicon layers in solar cells. CIGS also successfully replaces silicon in photovoltaics. Kesterite seems to be an ideal candidate for new, cheap and ecological friendly nanophotovoltaics.

The monograph should therefore play a ternary role. First, it should present the crystal structures of the known chalcogenides. Second, the monograph should explain a wide range of preparation methods and basic chemical properties of the known chalcogenides that can be important from a practical point of view. Third, the book should explain to the reader the possibility of transferring the relationships known in the domain of oxygen or nitrogen compounds to other groups of new chemical compounds, such as sulfides, selenides and tellurides. In this place, the use of the morphological classification of simple chemical species is very useful to preview some phenomena and relationships. The book will not be able, however, to completely fill the gap existing in the literature of chalcogenides, since crystal structures of many of them have not been confirmed .