Zr-Ce oxides as candidates for optically passive counter electrodes

Zr-Ce oxide films with compositions from pure Zr oxide to pure Ce oxide wer e made by reactive DC magnetron co-sputtering. The composition and structur e were determined by Rutherford backscattering and X-ray diffraction. Pure Ce oxide films have high charge capacity and are optically passive under ch arge insertion; they are, however, chemically unstable in an electrolyte of LiClO4 in propylene carbonate. Pure Zr oxide has practically zero charge c apacity. Zr-Ce oxide films have high (above 80%) optical transmittance, hig h charge capacity, and good chemical stability. These films remain fully tr ansparent irrespective of their degree of lithiation, which may be reconcil ed with electrons accommodating 4f states of Ce. (C) 1999 Elsevier Science B.V. All rights reserved.