Vibrational overtones quenching of near infrared emission in Er3+ complexes

Erbium organic complexes are receiving increasing attention in view of their application in polymeric telecommunication devices, but their use is limited by small emission quantum yield. Non-radiative deactivation of near IR (NIR) transition in Er3+ organic complexes is discussed on the basis of the electronic-vibrational energy transfer. Relevant transition matrix elements necessary to predict quenching effects exerted by various bonds located in the Er3+ coordination sphere are evaluated on the basis of an anharmonic Morse oscillator model and expressed as analytical functions of the fundamental vibrational intensities. The latter are calculated on the basis of various 'ab initio' quantum chemical methods, which yield intensity values close to the experimental measurements. Quenching effects in complexes containing a number of common ligands are evaluated and discussed, and a strategy to design highly efficient NIR emitters is proposed.