Investigation on light-trapping schemes in crystalline silicon thin-film solar cell on glass superstrate by ray tracer

Abstract

This paper presents investigation on light-trapping (LT) schemes in monocrystalline silicon (mono c-Si) thin-film solar cell on glass superstrate by ray tracer. In this work, solar cell with 20 μm c-Si thickness is studied. LT schemes involving silicon nitride (SiNx) anti-reflective coating (ARC), rear pyramids and back surface reflector (BSR) have been investigated. With incremental LT schemes, optical properties of the solar cell are analyzed within 300-1200 nm wavelength region. From absorption curve, maximum short-circuit current density (Jmax) is calculated, assuming unity carrier collection. From the ray tracing, planar reference solar cell exhibits Jmax of 25.70 mA/cm2. With SiNx ARC, the Jmax increases to 30.52 mA/cm2. This is attributed to enhanced broadband light-coupling into the solar cell. When rear pyramids are incorporated, the Jmax increases to 36.12 mA/cm2, due to increased long wavelength light scattering at the rear side of the cell. When the above LT schemes are combined with SiO2 and Ag BSR, Jmax up to 37.73 mA/cm2 (46.8% enhancement) is achieved. This is contributed by improved rear reflection and randomization of the long wavelength light by the BSR. Approach to reach Lambertian absorption in the 20 μm c-Si thin-film solar cell on glass superstrate is also discussed.