Fabrication of single junction amorphous silicon solar cell/mini module using novel n-type nanocrystalline SiO_x:F:H back reflector

A novel n-type nanocrystalline hydrogenated and fluorinated silicon oxide (nc-SiO_x:F:H) based back reflector layer (BRL) has been successfully developed for the fabrication of amorphous silicon based single junction solar cells by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique. Optoelectronic properties, particularly the refractive index (n) suitable for BRL were controlled by varying the oxygen content within the film without compromising the essential nanocrystalline growth. Surface morphology, structural and optical analysis of nc-SiO_x:F:H were investigated by using AFM, HRTEM, Raman, FTIR and Ellipsometer. Advantage of this nanocrystalline material as BRL has been demonstrated by incorporating it into a single junction amorphous silicon solar cell and compared its performance with conventional aluminium doped zinc oxide (ZnO:Al) and n doped hydrogenated microcrystalline silicon oxide (n-µc-SiO_x:H) based BRL. Single junction thin film a-Si solar cells with initial efficiency ~9.66 % have been successfully fabricated. It is found that the solar cell fabricated using newly developed BRL shows ~6 % more efficiency compared to n-µc-SiO_x:H based BRL. Spectral response studies revealed that the improvement was mainly due to enhanced response at visible as well as higher wavelength region.