BORON DOPED nc-Si:H WINDOW LAYER PREPARED BY HW-CVD FOR SOLAR CELL APPLICATIONS

In this work, we report on synthesis of boron doped hydrogenated nanocrystalline silicon (p-nc-Si:H) films by HW-CVD method. Films were prepared at low substrate temperature (165 °C) and low process pressure (20 mTorr) by varying diborane gas phase ratio [defined as RB2H6 = (FB2H6/FSiH4)×100%]. The material properties of these films are studied using micro-Raman spectroscopy, low angle X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, dark conductivity measurements etc. The correlation between RB2H6 and resulting material properties such as crystalline volume fraction, crystallite size, band gap and hydrogen content has been established. We have obtained high band gap (~ 2.48 eV) p-nc-Si:H films having dark conductivity (~ 0.6 S/cm) with low hydrogen content (~ 1.8 at. %) at high deposition rate (~19.2 Å/s). The employment of these films in a-Si:H based p-i-n solar cell as a p-type window layer could have low absorption losses thereby enhancing the current density which in turn would enhance the conversion efficiency of solar cell.