Effect of polymorphism on photovoltaic performance of CuAlO2 delafossite nanomaterials for p-type dye-sensitized solar cells application

In this paper, we report the successful hydrothermal synthesis of CuAlO2 nanocrystals, 3R or mixture of 2H and 3R polytypes. According to the literature, the potential of CuAlO2 with 2H and 3R polytype as cathode elements in DSSCs has not been fully explored by either theory or experiment. We have made a comparative study of nanocrystalline CuAlO2 polytypes prepared by hydrothermal method in subcritical conditions. The stability diagram for Cu-Al-H2O system allows preparing of nanocrystalline CuAlO2, either 3R pure phase or mixture of 2H and 3R. Together with temperature and autogenous pressure, the time reaction seems to be a key factor in the competition between both polytypes, 3R and 2H. The nanocrystalline CuAlO2 polytypes have been characterized from the structural and optical point of views prior to be used for DSSC preparation and characterization. We have notably found that even in small concentration, the presence of 2H polytype in CuAlO2 compound leads to an increase of 49% of the energy conversion efficiency compared to pure 3R-CuAlO2 polytype. The future work will be focused on the hydrothermal synthesis of pure nanocrystalline 2H-CuAlO2 polytype and the study of its effect on the performance of p-type DSSCs. (C) 2017 Elsevier Ltd. All rights reserved.