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In this study, the effect of wide-gap n-type μc-Si1-XOX:H film on the performance of hetero-junction μc-Si:H solar cells has been investigated. We have developed n-μc-Si1-XOX:H films by RF-PECVD (13.56 MHz) using a gas mixture of silane (SiH4), hydrogen (H2), 1%-hydrogen-diluted phosphine (PH3) and carbon dioxide (CO2) at a low substrate temperature of about 200°C. It was found that optical band gap (E04) of n-type μc-Si1-XOX:H films were increased to larger than 2.4eV with increasing CO2/SiH4 ratio and power density. Under the optimized condition, a film showed the E04 of 2.38 eV, dark conductivity (σd) of 0.086 S/cm, activation energy of 0.076 eV and crystal volume fraction (XC) of 37%. The effect of n-μc-Si1-XOX:H was confirmed by J-V characteristics and spectral response of the hetero-junction μc-Si:H solar cells. The short-circuit current (JSC) was increased from 23.1 mA/cm2 to 23.7 mA/cm2 and the spectral response in the long wavelength region was increased. Even if this observation needs further confirmation, our study demonstrated that wide-gap n-type μc-Si1-XOX:H films is beneficial for improving the performance of hetero-junction μc-Si:H solar cells.
Date of Conference: 19-24 June 2011