Double stack layer structure of SiNx/pm-Si thin films for downshifting and antireflection properties

In this work, we propose a double stack layer design of SiNx/pm-Si thin films by using dichlorosilane in plasma enhanced chemical vapor deposition (PECVD). Adequate deposition condition has been found to attain the average minimal reflectance corresponding to two different layers of SiNx and pm-Si at the suitable refractive index and thickness of the respective films. The average reflectance of the structure is reduced to ∼3% at normal incidence for a wavelength range from 190 to 1100 nm as in comparison to single layer of SiNx thin film structure. Furthermore, using transmission electron microscopy (TEM) presence of double layer stack and formation of silicon quantum dots (QD's) in the size regime of 3-4 nm has been found. Photoluminescence (PL) diminishment in the double layer structure as in comparison to the single layer of SiNx thin film confirms the effective absorption and total internal reflection induced due to the gradient refractive index. However, visible photoluminescence observed in the present work also remarks the downshift property from the thin film which could subsequently improve the efficiency in silicon solar cells. Present work highlights the prospective of novel structure for downshifting, antireflection and as an passivation coating in new generation of silicon solar cells.