Development of plasma-enhanced chemical vapor deposition microcrystalline silicon oxide as a replacement for N-type or back transparent conducting oxide layers in amorphous silicon single-junction solar cells

The n-type hydrogenated microcrystalline silicon oxide (mu c-SiOx:H(n)) thin films with varied electrical and optical properties were prepared. We employed mu c-SiOx:H(n) as a replacement for n-type hydrogenated amorphous silicon (a-Si: H(n)) or back transparent conducting oxide (TCO) layers in hydrogenated amorphous silicon (a-Si:H) single-junction solar cells. Compared to the standard cell with a-Si:H(n)/ITO/Ag back reflecting structure, the cell using a-Si: H(n)/mu c-SiOx:H(n)/Ag or mu c-SiOx:H(n)/Ag showed a similar or even better performance. This improvement of cell performance mainly arose from the increased short-circuit current density (J(SC)) that originated from the increased long wavelength (580-660 nm) absorption in the absorber confirmed by the quantum efficiency measurement. The "all plasma-enhanced chemical vapor deposition" (if the front TCO and metal contact are disregarded) process without TCO (indium tin oxide, ITO) sputtering can simplify the fabrication and result in better interface quality. Compared to the standard cell, the conversion efficiency of a-Si:H cells using an 80 nm thick mu c-SiOx:H(n)/Ag back reflecting structure was enhanced from 9.32% to 9.84%, with V-OC = 0.90 V, J(SC) = 14.84 mA/cm(2), and FF = 73.7%.