EFFECTS OF THE I-LAYER PROPERTIES AND IMPURITY ON THE PERFORMANCE OF A-SI SOLAR-CELLS

The relation between the opto-electric properties of an a-Si:H i-layer and the performance of a-Si solar cells are extensively investigated, paying careful attention to the controllable range of the opto-electric properties and the effects of the impurities. It is shown that even trace amounts (10(19) cm(-3) or less) of oxygen impurity in the i-layer affect the film properties and the solar cell performance. When the impurity concentration and other undesirable factors are suppressed, the mutual relationship among the i-layer properties becomes clear. Although there is a limitation in the controllable range of the properties of device-quality a-Si:H, techniques such as a hydrogen plasma treatment can improve the controllable range. Guidelines to design and optimize the i-layer for solar cells are discussed on the basis of these experimental results. A total-area conversion efficiency of 12.0% is achieved for a 10 cm x 10 cm integrated a-Si solar cell submodule.