PLASMA PROCESSES IN PV SOLAR CELLS (a-Si:H)

The state of the art of amorphous silicon thin films deposited in PECVD processes for solar cells applications is reviewed. Precursors such as silane, tri and tetra chloro-silane as monomers in Ar, H2 and Ar+H2 gas mixtures or pure silane plasmas were mainly used in the deposition of amorphous or micro-crystalline Si thin films. Reactions kinetics in the plasma bulk and in the plasma surface (solid) interactions as measured by mass spectrometry in real time, on line, show the governing species the particulate contamination's and the rate determining steps in the deposition process. The degradation of a-Si:H solar cells at intense illumination i.,e.,at elevated temperatures and the inhibition of the degradation processes by the addition of Ar to the silane plasmas will be discussed.