Broadband wavelength and wide-acceptance angle of the SiO2 sub-wavelength surface structure for solar cells using CF4 reactive ion etching

This study examines using sub-wavelength surface structure (SWS) anti-reflection (AR) coating with a broad wavelength range of low reflectance and wide-acceptance angles of incident light fabricated on solar cells for improving solar cell performance. The SWS AR coating consisted of TiO2 and SiO2 layers that had thicknesses of a quarter-wavelength and heights of 300-nm SiO2 nano-pillars on the top surface of the sub-wavelength structure. The sub-wavelength SiO2 nano-pillars were formed using a reactive ion etching process with CF4 that involved using silver nanoparticles as the etching masks. The reflective spectrum of the SWS AR coating was examined using software simulation and experimental measurement. The average reduced reflectance of SWS AR coating was less than 3% between 450 nm and 900 nm wavelengths. SWS AR coating improved solar cell performance in conversion efficiency and maximal output power (PMAX) at higher incident angle illumination. Therefore, at an incident angle of 60°, the conversion efficiency improvement was 52.9% and the PMAX was 55.8%, as compared with the cells that had two layers (TiO2/SiO2) of AR coating.

► The sub-wavelength SiO2 nano-pillars were formed using CF4 reactive ion etching.
► Average reduced reflectance of sub-wavelength-structure was less than 3%.
► At an incident angle of 60°, the conversion efficiency improvement was 52.9%.