Semi-transparent silicon-rich silicon carbide photovoltaic solar cells

Abstract

All silicon-rich silicon carbide (Si-rich Si_xC_1−x)-based single p–i–n junction photovoltaic solar cells (PVSCs) were fabricated by growing nonstoichiometric Si-rich Si_xC_1−x films through medium-temperature hydrogen-free plasma enhanced chemical vapor deposition. The Si-rich Si_xC_1−x-based thin-film p–i–n junction PVSCs exhibit improved power conversion efficiency when an intrinsic Si-rich Si_xC_1−x absorbing layer with a low C/Si composition ratio is added; amorphous Si (a-Si) particles are embedded in this absorbing layer. Lowering the [CH₄]/[CH₄ + SiH₄] fluence ratio from 0.5 to 0.3 reduces the C/Si composition ratio of Si-rich Si_xC_1−x films from 0.74 to 0.665. The absorbance of these films in the visible light region (400–800 nm) is substantially enhanced to 3.8 × 10⁵ cm⁻¹ by reducing the [CH₄]/[CH₄ + SiH₄] fluence ratio, which is up to one order of magnitude larger than that of crystalline Si. The open-circuit voltage and short-circuit current density of the indium tin oxide/p-Si_xC_1−x/i-Si_xC_1−x/nSi_xC_1−x/Al PVSCs are enhanced to 0.51 V and to 19.7 mA cm⁻², respectively, raising the conversion efficiency and filling factor to 2.24% and 0.264, respectively. Through hydrogen-free deposition of the Si-rich Si_xC_1−x p–i–n cells on a-Si based p–i–n cells, Si-rich Si_xC_1−x/a-Si hybrid tandem PVSCs exhibit enhanced conversion efficiency and an enhanced filling factor of 6.47% and 0.332, respectively.