THE INFLUENCE OF PLASMONIC AND DIELECTRIC INCLUSIONS ON ANTIREFLECTIVE PROPERTIES OF HOMOGENEOUS COATINGS FOR SILICON PHOTOVOLTAIC STRUCTURES

Abstract

Subject of Study. Theoretical analysis of the efficiency for the antireflective coatings based on plasmonic silver (Ag) and dielectric silicon (Si) nanoparticles is presented. We observe the increase of light absorption in the active layer, which is related to the optical resonant properties of considered nanoparticles. Characteristic property of the studied composite layer is its ability to combine the functions of electric contacts and anti-reflective coating. Method. Numerical calculations were performed in CST Microwave Studio with FDFD method (Finite Difference in Frequency Domain). The optical parameters of materials were extracted from the experimentally measured data available in literature. Geometrical parameters of composite layer – size and location of particles – were varied. Comparison of light absorption efficiency for different coatings on top of the active layer is presented: the homogeneous Indium Tin Oxide (ITO) layer, ITO layer with the spherical nanoparticle inclusions on the ITO surface, ITO layer with spherical nanoparticle bulk inclusions. Periodical lattices of particles with sizes of range between 15 and 80 nm were considered. Nanoparticles of this size have dominant dipole response. Main Results. Numerical calculations have shown that nanoparticle inclusions cause significant deformation of the absorption spectra with appearing of resonant pecularities in the wavelength range equal to 300-800 nm. It originates from the nanoparticle resonant features, which are similar to the resonant features of isolated nanoparticles. Absorption in the active layer decreases sharply at the resonant wavelength. Resonant response of nanoparticles placed on the ITO surface differs significally from the isolated ones: the resonant frequency and Q-factor decrease. It was shown that absorption in the active layer decreases by 25 % when the size of Ag and Si particles increases. Ag nanoparticles, placed in ITO layer on top of the active layer, show a monotonic decrease of integral absorption down to 30% with decreasing of nanoparticle size. Si nanoparticles of 50 nm radius have maximal influence on the absorption. Practical Significance. These results may be useful for understanding the physics of antireflective composite coatings with inclusions of nanoparticles for developers of silicon solar cells.

Keywords

• photovoltaics
• antireflection
• nanoparticles
• plasmon
• Mie-resonance