Hot-wire chemical vapor-deposited microcrystalline silicon in single and tandem n–i–p solar cells

Abstract This paper examines the potential of μc-Si deposited by hot-wire chemical vapor deposition (HWCVD) at a constant hydrogen dilution of 0.95, as absorber layer in n–i–p thin film solar cells. For a series of single junction cells onto plain stainless steel, the highest open circuit voltage (Voc) and Fill Factor (FF) were 0.54 V and 0.72. From J–V measurements at reduced light intensities, the change of the AM1.5-normalized FF values with light intensity was found to depend on the μc-Si i-layer thickness. This is attributed to the thickness evolution of the i-layer crystallinity, which influences the cell properties, particularly for i-layers thinner than 2.0 μm. For thicker layers the measurements clearly show drift-driven charge carrier collection. Tandem cells showed FF values as high as 0.77, which indicates the very high optoelectronic quality of the μc-Si material. A 2.0 μm cell on a textured back reflector shows an efficiency of 7.8%.