Amorphous silicon based solar cells deposited from H2-diluted SiH4 at low temperatures

Amorphous silicon based solar cells have been developed which have both improved initial conversion efficiency and greater resistance to light induced degradation. The improved initial efficiency arises from higher open circuit voltage which is a result of depositing the i-layer at lower temperatures from SiH₄ diluted in H₂. The improvement in open circuit voltage is substantially greater than would be expected from the small increase in optical bandgap that is observed as deposition temperature is lowered and there are indications that charge transport across the cell might change as the deposition temperature is lowered. By optimizing the deposition parameters the authors were able not only to reduce the total light-induced degradation, but to affect a qualitative change in the nature of the functional dependence of the conversion efficiency on light soaking time, so that after a few hundred hours of light soaking time the efficiency asymptotically approaches a limiting value (“saturation”)