Effect of PECVD process parameters on structural transition of a-Si/µc-Si thin-film solar cell and its operational parameters

Abstract

In the first part of this work the Plasma Enhanced Chemical Vapor Deposition PECVD process parameters; namely dilution ratios and substrate temperature, were controlled to build i-layer at low dilution ratios with moderate substrate temperatures. An intrinsic layer was deposited on Indium Tin Oxide glass by PECVD technique, with different dilution ratios of silane in hydrogen and different substrate temperatures to study the transition from amorphous to microcrystalline phase. The Si:H thin film was evaluated by field emission scanning electron microscopy, x-ray diffraction and atomic force microscopy. The structural transition between a-Si:H to μc-Si:H was achieved at dilution ratio 13.3 and substrate temperature 250°C with surface roughness 22.5 nm. This condition was used to build a p-i-n junction. The second part of the work included using the p-i-n junction as a substrate and applying a silver nanoparticles layer by Physical Vapor Deposition (PVD) technique at different substrate temperatures. The microstructure and the morphology of the entire silver deposited a-Si:H/μc-Si:H p-i-n junction was studied by FESEM and atomic force microscope AFM. The performance of the a-Si:H/μc-Si:H solar cell was evaluated by current-voltage measurements and optical absorption. It was observed that PVD silver nanoparticles layer deposited at 200°C had a surface roughness of 88nm, which resulted an increase in the optical absorbance to 74% at 300nm wavelength with a cell efficiency of 7.38%.