Development Of Stable A-Si Solar Cells With Wide-Gap A-Si : H I-Layers Deposited By An Inert Gas Plasma Treatment Method

The stability against light soaking of wide-gap hydrogenated amorphous silicon (a-Si:H) films and a-Si solar cells deposited by a newly developed inert gas plasma treatment method has been systematically investigated for the first time. The defect density (N-D) of a-Si:H films with an optical gap (E-opt) of 1.64 eV deposited by the inert gas (He, Ar, Xe) plasma treatment method was measured by a constant photocurrent method (CPM). E-opt was determined by (alpha h nu)(1/3) versus h nu plots. It was found that the inert gas plasma treatment method is capable of decreasing the initial and stabilized ND of the wide-gap a-Si:H films to a greater extent than that achieved by the 100% SiH4 process. In particular, the wide-gap a-Si:H film deposited using an Ar plasma treatment showed low initial and stabilized N-D of about 8 x 10(14) cm(-3) and 9 x 10(15) cm(-3), respectively, which are comparable to those of our optimized a-Si:H with E-opt similar to 1.57 eV deposited from 100% SiH4. It was also found that this deposition method is able to improve the stability of a-Si solar cells with wide-gap i-layers when compared to the 100% SiH4 process. Experimental results indicate that this deposition method can suppress the fast light-induced degradation which is probably caused by the light-induced defects that are difficult to recover by thermal annealing at similar to 150 degrees C.