Fabrication and Degradation Analysis of Perovskite Solar Cells with Graphene Reduced Oxide as Hole Transporting Layer

Currently, the stability of perovskite solar cells (PSCs) is a critical challenge for the commercialization of such devices. A challenge in the structure of these devices is the ordinarily used hole transporting layer (HTL) which suffers from long-term instability. Considering the promised features of graphene derivatives (including their chemical resistance), we applied the graphene oxide (GO) and its reduced form (rGO) as the HTL. Also, the perovskite layer was deposited through two different routes named single-step and double-step methods. rGO was synthesized using GO through a facile procedure and deposited on the base support of the perovskite layer. Then the effect of the perovskite layer coating method and the application of GO or rGO as HTL on the stability and efficiency of the solar cell were investigated. Endurance assessments were done by running the cell for a long time at more than 1 month (720 h) in a dark environment. We achieved a power conversion efficiency (PCE) of 3.28% for perovskite solar cells which were made by a single-step perovskite deposition method with rGO as HTL. After 1 month running in an ambient atmosphere without any encapsulation, 50% of PCE was retained. The results prove that the as-prepared rGO can be an effective replacement for the common hole transporting materials for PSCs and these structures show higher performance stability compared to commonly used PEDOT: PSS as HTL.