Enhancement of Spectral Response in μc-Si1-xGex:H Thin-Film Solar Cells with a-Si:H/μc-Si:H P-Type Window Layers

Abstract

The hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon (μc-Si:H) double p-type window layer has been developed and applied for improving microcrystalline silicon-germanium p-i-n single-junction thin-film solar cells deposited on textured SnO2:F-coated glass substrates. The substrates of SnO2:F, SnO2:F/μc-Si:H(p), and SnO2:F/a-Si:H(p) were exposed to H2 plasma to investigate the property change. Our results showed that capping a thin layer of a-Si:H(p) on SnO2:F can minimize the Sn reduction during the deposition process which had H2-containing plasma. Optical measurement has also revealed that a-Si:H(p) capped SnO2:F glass had a higher optical transmittance. When the 20 nm μc-Si:H(p) layer was replaced by a 3 nm a-Si:H(p)/17 nm μc-Si:H(p) double window layer in the cell, the conversion efficiency (η) and the short-circuit current density (JSC) were increased by 16.6% and 16.4%, respectively. Compared to the standard cell with the 20 nm μc-Si:H(p) window layer, an improved conversion efficiency of 6.19% can be obtained for the cell having a-Si:H(p)/μc-Si:H(p) window layer, with VOC = 490 mV, JSC = 19.50 mA/cm2, and FF = 64.83%.