Improvement of a-Si solar cells fabricated by mercury-sensitized photo-CVD using H2 dilution method

The high quality-wide bandgap i-layers prepared by the hydrogen dilution method were applied to a-Si solar cells fabricated by mercury-sensitized photo-CVD. It was found that the initial efficiency and stability of the cells were significantly improved compared to the undiluted one. This improvement was due to the increase in the quality and stability of an i-layer as confirmed by the dark I-V characteristics measurement of the solar cell. Two techniques for increasing the stabilized efficiency of the H₂-diluted i-layer-based solar cell were employed. First, the use of appropriate bandgap profile leads to the increase in J_ac while maintaining high FF, resulting in the increase in the stabilized efficiency. Another one is the improvement of V_oc of the solar cell by the optimization of the p- and buffer layer. By lowering the temperature of p- and buffer layers, a solar cell with V_oc as high as 0.990 V has been obtained