New three-layer antireflection/surface passivating coating for high efficiency III-V compound solar cells

We use a chemically grown, thermally and chemically stable oxide, not only for surface passivation but also as an integral part of a 3-layer antireflection (AR) coating for thermally diffused p⁺n InP solar cells, thus solving the dual problem of surface passivation and surface reflection reduction on these cells. A phosphorus-rich interfacial oxide, In(PO₃)₃, is grown at the surface of the p⁺ emitter using an etchant based on HNO₃, o-H₃PO₄ and H₂O₂. This oxide has the unique properties of passivating the surface as well as serving as a fairly efficient antireflective layer. We show that it is possible to design a three-layer AR coating for a thermally diffused p⁺n InP solar cell using the In(PO₃)₃-grown oxide as the first layer and either ZnS, MgF₂ or a new combination MgF₂ as the second and third layers respectively, so as to yield an overall theoretical reflectance of less than 2%