First Principles Investigation of Electronic Properties and High Refractive Index of Rutile TiO2 for Photovoltaic Applications

Anti-reflective layer is an essential component of photovoltaic devices, used to reduce the well-known problem of light reflection. Deposed on the silicon wafers, this glass cover significantly contributes to raise the photovoltaic solar cells efficiency. For this purpose we used different dielectric materials, namely titanium dioxide TiO2. In the present work, we report the optimized structure, electronic band structure, density of states (DOS), partial density of states (PDOS) and optical properties of bulk rutile phase of titanium dioxide (TiO2). The density functional theory based upon the pseudo-potentials method as implemented in the first principle Quantum Espresso (QE) code has been employed. We performed a plane wave self-consistent field calculation of the ground state energy with both local density approximation (LDA) and generalized gradient approximation (GGA). Optical properties such as refractive indices, depending on the ordinary and extraordinary polarization directions, have been evaluated from the frequency-dependent complex dielectric function. Moreover, the obtained band structures, DOS and PDOS confirm that the valence and conduction bands of rutile are mainly formed by O-2p and Ti-3d states respectively. This substantiates the existence of high interactions between titanium and oxygen atoms. The large optical anisotropy has been studied through the calculation of the band structure and DOS. Our results are in good agreement with previous theoretical and experimental measurements.