Patent ID: 8071872

Claim:
A device for converting radiation to electrical energy comprising; active layer for converting incident radiation to electrical energy comprising a Group IV semiconductor; transparent substrate; and transparent barrier layer consisting of one or more rare earth compounds; wherein the barrier layer separates the active layer and the substrate and substantially prevents unwanted ions from the substrate migrating to the active layer wherein the active layer comprises one or more layers of a large band gap material; and one or more layers of a small band gap material; wherein the large band gap material is chosen from a group consisting of rare-earth oxide (RE x O z ), rare-earth germanium oxide (RE x Ge y O z ), rare-earth silicon oxide (RE x Si y O z ), rare-earth-silicon-oxide-phosphide (RE x Si y O z P w ), rare-earth-silicon-oxide-nitride (RE x Si y O z N w ), rare-earth-silicon-oxide-nitride-phosphide (RE x Si y O z N w P q ) wherein X, Z>0 and Y, W, Q are â‰§0, such that the band gap is greater than about 3 eV and wherein said small band gap material is chosen from a group consisting of rare-earth-silicon (RE x Si y ), rare-earth-germanium (RE x Ge y ), rare-earth-phosphide (RE x P y ), and rare-earth-nitride (RE x N y ) and mixtures thereof and wherein X, Y>0 and said small band gap is less than about 3 eV.