Influence of Hydrogen Plasma on the Defect Passivation of Polycrystalline Si Thin Film Solar Cells

Hydrogen passivation (HP) of polycrystalline silicon (poly-Si) thin film solar cells was performed in a parallel plate radio-frequency (rf) plasma setup. The influence of hydrogen pressure p and electrode gap d on breakdown voltage V-brk is presented showing that the minimum in V-brk shifts with higher pressures towards higher p . d values. Cell test structures provided by CSG Solar AG were used to examine the influence of p and d on the open circuit voltage V-OC. The highest V-OC's were achieved for p . d values that correspond to a minimum in V-brk. HP strongly improved the V-OC. After the hydrogen plasma treatment the V-OC improved significantly by a factor of 2 and amounted to 450 mV. Optimized parameters were then applied to different poly-Si solar cells prepared by electron beam evaporation.