The absorption and emission properties and film structure of co-evaporated mixed thin solid films of vanadylphthalocyanine (VOPc) and N,N'-bis(neopentyl)-3,4,9,10-perylenebis(dicarboximide) (BNPTCD) are reported. Exciplex emission from mixed films is clearly identified and the intensity of new near-infrared light source depends on the degree of mixing and molecular orientation in the film that control the exciplex. formation. A clear correlation between molecular organization and emission properties is established. The IR spectroscopic data and AFM topographical analysis show that thermal annealing of the mixed films induces phase separation enhancing energy transfer as main deactivation pathway of the absorbing BNPTCD molecules. (C) 2003 Elsevier B.V. All rights reserved.