Method for low temperature plasma enhanced chemical vapor deposition

Abstract

A sequential plasma-enhanced chemical vapor deposition (PECVD) of SiN and SiO.sub.x produces a very effective double-layer antireflection coating. This antireflection coating is compared with the frequently used and highly efficient double-layer MgF.sub.2 /ZnS coating. It is shown that the double-layer SiO.sub.x /SiN coating improves the short-circuited current (J.sub.sc) by 47%, open-circuit voltage (V.sub.oc) by 3.7%, and efficiency (Eff) by 55% for silicon cells with oxide surface passivation. The counterpart MgF.sub.2 /ZnS coating gives smaller improvement in V.sub.oc and Eff. However, if silicon cells do not have the oxide passivation, the PECVD SiO.sub.x /SiN gives much greater improvement in the cell parameters, 57% in J.sub.sc, 8% in V.sub.oc, and 66% in efficiency, compared to the MgF.sub.2 /ZnS coating which improves J.sub.sc by 50%, V.sub.oc by 2%, and cell efficiency by 54%. This significant additional improvement results from the PECVD deposition-induced surface/defect passivation. The internal quantum efficiency (IQE) measurements showed that the PECVD SiO.sub.x /SiN coating absorbs fair amount of photons in the short-wavelength range (<500 nm), however, the improved surface/defect passivation more than compensates for the loss in J.sub.sc and gives higher improvement in the cell efficiency compared to the MgF.sub.2 /ZnS coating.