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

Abstract

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 R B 2 H 6 = ( F B 2 H 6/ F SiH 4)×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 R B 2 H 6 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.