Hydrogenated amorphous silicon oxide (a-SiO:H) films were prepared by rf glow discharge decomposition of SiH4, C02 and H2 gas mixture. These films showed better properties than a-SiC:H films. By applying the a-SiO:H to the player, we attained an efficiency of 12.5% for 1cm 2 single junction solar cells and a total-area efficiency of 10.1% for 30cm x 40cm tandem submodules.

Dark current-voltage (J-V) characteristics of p-i-n a-Si solar cells are studied to clarify the effect of the p/i interface layer on the open-circuit voltage (Voc). It is shown that the recombination current in the p/i interface region is predominant in the a-Si solar cells with an i-layer thickness of less than 200 nm and has a great effect on the dark-current transport in the solar cells. It is also shown that the current transport of the cells with the p/i interface layer of constant band gap of a thickness of more than 14 nm is effectively the same as that of a cell in which the band gap of the whole i layer is equal to that of the interface layer. A model in which the dark current of the cell consists of the recombination current at the p/i interface and the recombination current in the bulk region of the i layer is proposed. Using this model, the Voc degradation for the a-Si solar cells with the p/i interface layer is shown to be due to the defects generated in the i layer.

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