Towards a general concentration quenching model of Bi3+ luminescence

The vacuum referred binding energy of the electron in the Bi2+ ground state has been determined in 15 different compounds. This shows that the electron binding energy in the ground state of Bi2+ is at lower (more negative) energy compared to the electron binding energy in the excited state of Bi3+. This means that electron transfer from the excited state of one Bi3+ to a neighboring Bi3+, forming a Bi2 + -Bi4+ pair, acts as a quenching route for the Bi3+ emission. Electron back transfer in the Bi2 + Bi4+ pair is then suggested to be the origin for the frequently observed pair emission. This paper shows that vacuum referred electron binding energy diagrams can provide a unique physical insight in the properties of inorganic compounds.