Preparation of p-type AgCrO₂ nanocrystals through low-temperature hydrothermal method and the potential application in p-type dye-sensitized solar cell

The synthesis of nano-sized ternary delafossite oxides with pure crystal phases is of great challenge. We present a novel hydrothermal method for the synthesis of AgCrO2 nanocrystals with ultrafine size of 10–20 nm at relatively low temperature range (190–230 C). It is the first time to report that AgCrO2 nanocrystals can be hydrothermally synthesized at such a low temperature (190 C) and applied as photocathode in dye sensitized solar cells (DSSCs). The as-synthesized AgCrO2 nanoproducts, including their crystal phases, morphologies, element compositions, valence state information, thermal stability, electrical and optical properties, have been systematically studied. This facile method employed metal nitrates (AgNO3 and Cr(NO3)3) as the starting materials and NaOH as the mineralizer, where Cr(NO3)3 undertook the dual functions of Cr3+ source material and weak reducing reagent. The in-situ oxidation–reduction reaction between Cr3+ and Ag+/Cu2+ during the hydrothermal crystal growth is the noteworthy feature of this general method. The crystal formation mechanism disclosed in the synthesis of chromium based delafossite oxides will certainly be benefit for the preparation of other delafossite oxides.