Preparation of high quality widegap a-Si:H films and its application to a-Si solar cells

The novel film formation method of alternately repeating a-Si deposition and hydrogen plasma treatment (ADHT method) was studied. The optical bandgap could be changed from 1.67 to 1.98 eV, the defect densities under 1/spl times/10/sup 16/ cm/sup -3/ were obtained at wide range of optical bandgap, and the saturated defect densities after light soaking were about 3/spl times/10/sup 16/ cm/sup -3/. Single junction pin a-Si solar cells with i-layer formed by ADHT method were stable to light soaking. Applying the these widegap a-Si films to the i-layer of top cell of 2-stacked tandem solar cells, high open circuit voltage of 1.85 V and high efficiency of 10.5% was attained.