La0.5Sr0.5CoO2.91@RGO nanocomposites as an effective counter electrode for dye-sensitized solar cells

The role of the counter electrode (CE) in dye-sensitized solar cell (DSSC) is to collect electrons from the external circuit and reduce I 3 − to I − in the electrolyte. In this paper, the perovskite-phase La0.5Sr0.5CoO2.91 (LSCO) nanoparticles were synthesized through a sol–gel method and used as the CE for DSSC. The cell showed a power conversion efficiency (PCE) of 3.24 %. To further improve the PCE of CE of the LSCO nanoparticles, the nanocomposites of the LSCO nanoparticles with reduced graphene oxide (LSCO@RGO) have been prepared via a simply physical mixing method and served as the efficient CE for DSSC. The LSCO@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the positive synergetic effect between LSCO nanoparticles and RGO sheets. As a consequence, the DSSC with the LSCO@RGO nanocomposites CE yielded a PCE of 6.32 %, which is observably higher than that of using pristine LSCO CE (3.24 %) or RGO CE (4.54 %) alone, and up to 88 % of the Pt CE (7.18 %).