We report the luminescence characteristics of Sr(S,Se):Ce,Cl thin film electroluminescent devices, fabricated by co‐evaporation of SrS:Ce,Cl pellet and elemental Se. From the electroluminescence spectra measurements for varied S:Se mole ratio and temperature, it is found that the relative intensity of green emission band to blue emission band decreases with increasing lattice constant of the host lattice. This can be qualitatively accounted for as being caused by a nonradiative energy transfer from the emission band of Ce3+to the absorption band due to defects associated with anion vacancies in the host lattice. ©1995 American Institute of Physics.