Structural and Solar Conversion Characteristics of the ( Cu2Se ) x ( In2Se3 ) 1 − x System

Abstract

Members of the title system were prepared by direct syntheses and studied by means of x‐ray diffraction, electron microprobe analyses, and photoelectrochemistry. We found three new hexagonal phases in the low region , all of which can be understood in terms of Se close packing. They provide indications for the occurrence of polytypism. Two of the three previously reported phases with cubic stacking were found in the less Cu‐poor part. This region of cubic stacking extends from at least to . was found to be the end member of the cubic stacking region, and its frequent recurrence in various synthesis attempts indicates its stability. This compound, as well as all others identified in this study (e.g., ), were photoelectrochemically active with some variability. Their optical bandgaps all fell between 0.9 and 1.3 eV. Two mixed sulfoselenides were prepared as well. One of them with possessed the normal chalcopyrite structure and a direct optical bandgap that corresponded to what one would expect for such a mixed sulfide‐selenide. Close to the nominal stoichiometry , we did not find the spinel phase as found for ; instead, we found two different polytype phases for the pure selenide and the sulfoselenide.