Effect of Spinel Inversion on (CoxFe1-x)(3)O-4 All-Oxide Solar Cell Performance

Oxide materials have been widely investigated for use as absorber layers in high-performance solar cells, and in this study combinatorial methods were used to specifically investigate cobalt-iron (Co-Fe) oxide composites. Structural inversion of Co-Fe oxides from a normal to an inverse spinel structure occurs at the critical composition of approximately 33% Fe added to Co, causing changes in the crystallinity, symmetry, sub-lattice vibrational modes, optical bandgap, and electrical resistivity. When used as an absorber layer in all-oxide solar cells with the multi-layered geometry of glass|FTO|TiO2|Co-Fe-O|Au, enhanced photovoltaic performance was observed, with a maximum V-oc of 534mV at a composition of approximately 45%Fe and a 200% improvement in P-max compared to cobalt-rich devices. Using combinatorial data maps of the various material properties, a significant correlation between the solar cell properties and the chemical composition of the Co-Fe-O layer was revealed. This correlation allows for a better understanding of the Co-Fe-O system, which is a necessary step towards the development of Co-Fe-O-based all-oxide solar cells.