Compositional trends and the photoluminescence of phosphorus selenide glasses

The first cw photoluminescence measurements on a range of glassy phosphorus-selenium alloys are presented, including measurements of the emission and excitation spectra. The trends in the positions of these in energy are discussed in terms of the variation of the optical band gap with composition. It is thought that the electronic states in these materials may arise either from isolated molecules in a matrix, or from a polymerised, continuously bonded network derived from these molecules. The inadequacies of the polymeric model applied to the PSe system are examined and possible appropriate forms for the average coordination number are discussed. It is concluded that the structural model involving molecular cages in a matrix appears to be necessary to understand the electronic properties of these materials.