Green Synthesis of Eco-Friendly Graphene Quantum Dots for Highly Efficient Perovskite Solar Cells

With regard to perovskite solar cells (PSCs), a zinc oxide (ZnO) planar architecture has significant advantages from the upscaling perspective in terms of cost effectiveness and low-temperature processing compared to architectures with a mesoporous titanium dioxide (TiO2) layer. Nevertheless, the perovskite (PVK) materials are unstable on a ZnO electron transport layer (ETL) during the annealing process. Herein, we discovered that the PVK material on top of the ETL changes to lead iodide (PbI2) because of the presence of oxygen agents on the surface of ZnO. To tackle this issue, a hybrid photoelectrode of ZnO/graphene quantum dots (GQDs) is prepared and used as an ETL. As a result, green synthesized GQDs not only passivate the oxygen agents on the surface of the ZnO but also extract electrons rapidly from the PVK film to decrease the recombination of electron–hole pairs. Herein, findings reveal that PSC on ZnO:GQD ETL shows a power conversion efficiency (PCE) of up to 17% on fluorine tin oxide (FTO) under AM1.5G illumination. Consequently, the introduction of multifunctional GQD as an additive in ZnO ETL in PSCs displays a new and efficient tool in terms of environmental impact and economic feasibility for PSC commercialization.