Free-standing flexible carbon electrode for highly efficient hole-conductor-free perovskite solar cells

A free-standing thermoplastic carbon film with good flexibility and conductivity has been developed and introduced in perovskite solar cells for the first time. Due to its thermoplasticity, this free-standing carbon film can be directly hot pressed onto the perovskite layer as counter electrode. By optimization toward the components of carbon films and hot-pressing pressure, the back contact between the perovskite and carbon films has been significantly improved. Up to 13.53% of power conversion efficiency has been achieved, which is one of the highest efficiencies for hole transporting material-free perovskite solar cells. This kind of flexible carbon electrodes with the advantages of low-cost, simple and low-temperature (<100 °C) preparation process and high efficiency, show great potential application in perovskite solar cells.