Electronic structure and optical properties of In2X2O7 (X=Si, Ge, Sn) from direct to indirect gap: An ab initio study

Electronic optical properties of In 2 X 2 O 7 (X = Si, Ge, Sn) compounds were calculated using density functional theory (DFT) calculation based on full potential linear augmented plane wave (FPLAPW). Four schemes LDA, GGA, EVGGA and mBJ were used to solve exchange correlation factor. The calculations of In 2 X 2 O 7 show that mBJ give better band splitting. The band structure of In 2 Ge 2 O 7 show an indirect band gap (X → Г) of about 3.55 eV while In 2 Si 2 O 7 and In 2 Sn 2 O 7 exhibit direct band gap (Г → Г) of 5.59 eV and 2.44 eV. The frequency dependent dielectric functions of In 2 X 2 O 7 compounds show the highest transparency at the infrared (IR) region. The In 2 Si 2 O 7 and In 2 Ge 2 O 7 are broad band semiconductors starting from ultraviolet (UV) region while In 2 Sn 2 O 7 start from visible region. The reflectivity spectra shows that In 2 X 2 O 7 compounds are suitable for antireflection coating layer in solar cells and filters in far UV region. As In 2 Si 2 O 7 and In 2 Sn 2 O 7 are a direct band gap material, that make them suitable for light emitting diodes (LED’s). In 2 Si 2 O 7 is suitable for UV light while In 2 Sn 2 O 7 is fit to emit green, blue and violet light. The present work provides information about variation of the electronic and optical properties by replacing Si by Ge and by Sn in the pyrochlore oxide which helps to understand the electronic and optical properties of this group of compounds.