Influence of Excitation Frequencies (81.36 - 120 MHz) in the VHF-PECVD Technique on the Deposition Rate and Properties of Silicon Thin-Film Solar Cells

The influence of plasma excitation frequency (81.36 – 120 MHz) on hydrogenated amorphous silicon (a-Si:H) deposition was examined and will be presented. Intrinsic amorphous silicon has been deposited by very high frequency plasma enhanced chemical vapour deposition technique at the substrate temperature of 160°C. First, the study of plasma homogeneity was performed. The excitation frequency was varied between 81.36 and 120 MHz. Then, the changes in the material properties of intrinsic a-Si:H related to variation of deposition parameters at 120 MHz have been analyzed. Special emphasis was given to the effect of working pressure and silane concentration on layer properties and deposition rate. Finally, the p-i-n solar cell structures with implemented intrinsic a-Si:H absorber layers prepared at 120 MHz excitation frequency at different deposition parameters were fabricated. As a result, single-junction p-i-n solar cell with efficiency of 8.7% was deposited at 0.9 nm/s deposition rate.