Quantum chemical modelling of ‘green’ luminescence in self activated perovskite-type oxides

We discuss the origin of the intrinsic visible band emission of ABO3 perovskite oxides (so-called ‘green luminescence’) which remains a topic of high interest during the last quarter of the century. We present a theoretical calculation modelling of this emission in the framework of a concept of charge transfer vibronic excitons [Phys. Solid State, 40 (1998) 834], i.e. as a result of radiative recombination of correlated (bound) self-trapped electron and hole polarons in the highly polarizable ABO3-type matrix. The Intermediate Neglect of Differential Overlap method combined with the Large Unit Cell periodic defect model was used for quantum chemical calculations and theoretical simulation of the green emission for a series of model ABO3 perovskites. The ‘green’ luminescence energies for PbTiO3, SrTiO3, BaTiO3, KNbO3 and KTaO3 perovskite-type crystals agree well with those experimentally observed earlier.