Improvement of p-i buffer layer properties by hydrogen plasma treatment and its applications to pin a-Si:H solar cells

The performance of p-i buffer layers in pin amorphous silicon solar cells was improved by a method of alternately repeating deposition and hydrogen plasma treatment (ADHT). The ratio of SiH₂/SiH of a-SiC:H films was minimized and the photoconductivity was maximized at a certain treatment time. The optical bandgap of the a-SiC:H film was increased by the hydrogen plasma treatment while the hydrogen contents were almost constant. The ADHT method was also examined for improving the film properties and cell characteristics. The change of performance of the solar cells corresponded to that of a-SiC:H film properties of photoconductivity and the SiH₂/SiH ratio against the hydrogen plasma treatment time. The wide optical bandgap and the high photoconductive a-Si:H film without carbon was deposited by the ADHT method. The solar cell conversion efficiency obtained for a-Si:H buffer layer was equal to that with a-SiC:H buffer layer. With the use of the high performance p-i buffer layer deposited by ADHT method, a cell conversion efficiency of 13.2% was obtained