Quality improvement in a-Si films and their application to a-Si solar cells

A theoretical analysis conducted in order to raise the efficiency of amorphous-silicon (a-Si) solar cells is discussed. Based on the analysis, the quality of the i and p layers was improved. A high-quality a-Si film with a lower impurity concentration and lower defect density than conventional films was fabricated using the super chamber. A reduction in damage to the transparent conductive oxide and an improvement in p and i interface properties was achieved by using a photo-CVD method. This same method was used to study superlattice structure films, to fabricate high-conductivity films with a wider optical bandgap than conventional a-SiC films, and to improve sensitivity in the short-wavelength region. B(CH₃)₃ was used as a p-type doping gas for a-Si film that had a higher quality than that fabricated using B₂H ₆. These technologies made possible a conversion efficiency of 11.7% for 1-cm² single-junction solar cells and a total area conversion efficiency of 9.60% for 100-cm² single-junction integrated-type submodules