Towards high-performance dye-sensitized solar cells by utilizing reduced graphene oxide-based composites as potential alternatives to conventional electrodes: A review

Dye-sensitized solar cells (DSSCs) have recently emerged as one of the most promising new-generation photovoltaic devices due to their facile fabrication protocols, capacity to operate under diffuse light, and low-impact on the environment. However, their low power conversion efficiency (∼15.2%) hinders practical applications. This is primarily owing to ineffective dyes, significant recombination at solid/liquid interfaces, and limitations of TiO2, the conventional photoanode material, especially poor light harvesting and electron transport. Moreover, Pt, the traditional counter electrode material, is costly and unstable due to its scarcity and low corrosion resistance to I3ˉ, respectively. This increases the device cost and shortens its lifespan. Inspired by this, current research interests have shifted their focus from traditional materials to low-cost alternatives, including metal oxides, metal chalcogenides and perovskites, which offer competitive photovoltaic performance. Nonetheless, these alternative materials exhibit relatively low electrical conductivity, which compromises device performance. Thus, to improve device efficiency and sustainability, these materials have recently been coupled with highly conductive and stable carbon nanomaterials, particularly graphene-based materials. Among them, reduced graphene oxide (rGO) has been more appealing due to its compatibility with low-cost solution processing. Therefore, this review highlights the recent advances in DSSC efficiency and sustainability made over the last five-years (2020–2024) by developing TiO2-free photoanodes and Pt-free counter electrodes, in particular, by introducing rGO into metal oxides, metal chalcogenides and perovskites. Challenges and future directions for fabricating TiO2- and Pt-free DSSCs are discussed to close the gap between emerging nanomaterials and their traditional counterparts, thereby setting the stage for commercialization.