Current status and trends of carbon-based electrodes for fully solution-processed perovskite solar cells

Perovskite solar cells (PSCs) have revolutionized photovoltaic research. As a result, a certified power conversion efficiency (PCE) of 25.5% was recorded in late 2020. Although this efficiency is comparable with silicon solar cells; some issues remain partially unsolved, such as lead toxicity, instability of perovskite materials under continuous illumination, moisture and oxygen, and degradation of the metallic counter electrodes. As an alternative to tackle this last concern, carbon materials have been recently used, due to their good electrical and thermal conductivity, and chemical stability, which makes them one of the most promising materials to replace metallic counter electrodes in the fabrication of PSCs. This review highlights the recent advances of carbon-based PSCs, where the carbon electrode (CE) is the main actor. CEs have become very promising candidates for PSCs; they are mainly fabricated using a simple combination of graphite and carbon black powders embedded in a binder matrix, giving a paste that is then solution-processable, resulting in devices with improved quality stability, when compared to metallic electrodes. In this review, CE’s composition is emphasized, since it can give both, high and low-temperature processed electrodes, compatible with different device configurations. Finally, the tendencies and opportunities to use CE in PSCs devices are presented.