Low-temperature-processed a-SiOx:H/a-Si:H tandem cells for full spectrum solar cells

Abstract

We developed wide-bandgap amorphous silicon (a-Si:H) and amorphous silicon oxide (a-SiOx:H) absorbers by extremely decreasing deposition temperature to as low as 100 degrees C. By adjusting hydrogen and carbon dioxide gas flow rates, device-quality absorbers and thus suitable single junction cells were obtained. An a-SiOx:H single-junction cell (i = 100 nm) fabricated employing the absorber we developed showed an open circuit voltage (V-oc) of 1.007V and a fill factor of 0.741, which are better than those of a-Si:H cells. This a-SiOx:H cell was introduced in a-SiOx:H/a-Si:H tandem cells as the top cell, which contributed to the achievement of a markedly high V-oc of 1.910 V. This tandem cell with an efficiency of 9.25% showed better V-oc and current matching property than the a-Si:H/a-Si:H (8.74%) tandem structure. The low-temperature-gradient a-SiOx:H/a-Si:H tandem cells can be a promising configuration for spectrum splitting applications. (C) 2015 The Japan Society of Applied Physics