The properties of photonic crystals that allow or inhibit the propagation of electromagnetic (EM) waves in between photonic band gap (PBG) regimes have proved to be significant. In this work, we investigated the PBG analysis of one-dimensional TiO2/SiO2 photonic crystal using plane wave method (PWM). The PBG width depends of on the various optical parameters such as lattice constant (Λ), center wavelength (λc), thickness of the layers (d), dielectric constant (ε) and refractive indices (n). Among various parameters, the center wavelength (300-1100nm), the thickness of TiO2 (28-103 nm) and SiO2 (51-189 nm) layers were optimized for the tuned bandgap. The obtained results revealed that the PBG shifting towards the lower frequency region and reducing the size due to the increment of center wavelength and thicknesses. This result is useful for the understanding the way of photon propagation within artificial structure and it could be possible for the better back reflector in thin film solar cells.

In this work, we have adopted a sol-gel spin-coating technique and prepared alternative TiO2/Si3N4 multilayers on glass substrates. These alternating layers of TiO2/Si3N4 thin film samples were calcinated at two different temperatures and studied for their optical performance. The optical properties of fabricated thin films were investigated by UV-Visible spectrophotometer, X-ray diffractometer (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy. UV-visible spectra showed broader and higher optical reflectance in the visible spectral region. FTIR transmission spectra show Ti-O-Ti and Si-N stretching modes at around 600 and 881 cm-1. XRD pattern confirmed the presence of anatase-TiO2 and α-Si3N4 phases. Finally, Raman spectra revealed the presence of anatase-TiO2 and N-Si vibration modes.

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Enhanced conversion efficiency with reduced cost of thin film solar cell is the primary objective of the scientific community. Light trapping mechanism is essential which have been explored and improved the performance of the solar cell. Past few decades, the plasmonic solar cell has been investigated in which actively involves metal nanostructure like nanoparticle or grating. Our numerical work analyzes the light absorption enhancement in the 1µm thin c-Si solar cell with different nanostructures. The optimal design combines front dielectric (ITO) and back metal (Ag) gratings as the reflector. This designed cell shows enhanced absorption through localized surface plasmon (LSP) or surface plasmon resonance (SPR). Comparing reference, the dual grating solar cell provides a significant efficiency from ~11% to 18.82%, which is a 71% enhancement. This enhancement has been attributed to the field localization and resonantly field scattering at the interface of the metal and active region.