ABSTRACTThe temperature dependence of photoluminescence in SrS singly and doubly doped with Eu2+, Sm3+ was studied with different excitation energies. Different energy transfer mechanisms, namely, phonon-assisted energy transfer and electron transfer through energy bands, depending on the excitation energy, are proposed to take place in SrS:Eu2+, Sm3+ thin films. We estimate that under UV light excitation 10% of Eu2+ emission originates from electronic transitions between Eu2+ and Sm3+ through the conduction and valance bands. In contrast, direct inter-ionic transitions take place for 2.84 eV excitation energy via a phonon assistance mechanism.
The Evolution of Intermolecular Energy Bands of Occupied and Unoccupied Molecular States in Organic Thin Films