Effect of Hydrogen Dilution Near the p/i Interface Region of a-Si:H p-i-n Solar Cells

It is known that the a-Si:H solar cell with H-diluted i-layer (p-iH-n) exhibits a better stability under AM1 light exposure than the non-diluted solar cell (p-i-n). Recently, Wang et al. found that the a-Si:H solar cell when inserting a thin H-diluted i-layer between the p- and the i-layer (p-iH-i-n) shows the same stability as the p-iH-n solar cell after 600 hours light soaking. It was suggestedthat the stabilization of a H-diluted a-Si:H solar cell is through controlling its p/i interface. In this work, we report the electroluminescence (EL) measurements of a-Si:H solar cells with p-iH-n, p-iH-i-n and p-i-n structures made in identical conditions except the difference in H-dilution processing. EL spectra in a wide range of temperature indicate that the defect-band emission can becontrolled through a thin H-diluted i-layer near the p/i interface region, but the main-band emission depends more on the diluted i-layer thickness. According to the temperature dependence of the EL efficiency, the valence band-tail width of the active layer in the p-iH-i-n cell is estimated to be about 13% broader than that in the p-iH-n cell. From the total EL intensity as a function of theforward current density, the recombination processes at room temperature are suggested to be a monomolecular type for p-iH-n, p-iH-i-n, and p-i-n structures.