Due to growing demand on discovering new materials for light-emitting diodes devices, many efforts were made to discover and characterize new inorganic materials such as phosphors. Using the full potential method within density functional theory the electronic and optical properties of BaAl2Si3O4N4 and BaAlSi4O3N5 semiconductors have been investigated. The electronic structure and the optical properties of these phosphors were calculated through a reliable approach of modified Beck-Johnson (mBJ) approach. We found that BaAl2Si3O4N4 and BaAlSi4O3N5 have wide direct band gaps positioned at G about 5.846 and 4.96 eV respectively. The optical properties, namely the dielectric function, optical reflectivity, refractive index and electron energy loss, are reported for radiation up to 15 eV. Our study suggests that BaAl2Si3O4N4 and BaAlSi4O3N5 could be promising materials for applications in the LEDs devices and optoelectronics areas of research. (C) 2015 Elsevier B.V. All rights reserved.