Efficient hole-conductor-free, fully printable mesoscopic perovskite solar cells with carbon electrode based on ultrathin graphite

Ultrathin graphite has been applied in hole-conductor-free, fully printable mesoscopic perovskite solar cells as counter electrode. It was found that ultrathin graphite effectively increased the specific surface area of the carbon layer without sacrificing the conductivity. The large specific surface area facilitated the hole collection from the perovskite to carbon layer, correspondingly decreased the charge transfer resistance at the perovskite/carbon interface. Besides, the penetration of perovskite precursor solution in the carbon layer was accelerated due to the highly interconnected channels. As a result, the power conversion efficiency of the printable mesoscopic perovskite solar cell was significantly improved from 12.63% to 14.07% by incorporating ultrathin graphite instead of bulk graphite.