Versatility of Carbon Enables All Carbon Based Perovskite Solar Cells to Achieve High Efficiency and High Stability

Carbon-based perovskite solar cells (PVSCs) without hole transport materials are promising for their high stability and low cost, but the electron transporting layer (ETL) of TiO2 is notorious for inflicting hysteresis and instability. In view of its electron accepting ability, C-60 is used to replace TiO2 for the ETL, forming a so-called all carbon based PVSC. With a device structure of fluorine-doped tin oxide (FTO)/C-60/methylammonium lead iodide (MAPbI(3))/carbon, a power conversion efficiency (PCE) is attained up to 15.38% without hysteresis, much higher than that of the TiO2 ones (12.06% with obvious hysteresis). The C-60 ETL is found to effectively improve electron extraction, suppress charge recombination, and reduce the sub-bandgap states at the interface with MAPbI(3). Moreover, the all carbon based PVSCs are shown to resist moisture and ion migration, leading to a much higher operational stability under ambient, humid, and light-soaking conditions. To make it an even more genuine all carbon based PVSC, it is further attempted to use graphene as the transparent conductive electrode, reaping a PCE of 13.93%. The high performance of all carbon based PVSCs stems from the bonding flexibility and electronic versatility of carbon, promising commercial developments on account of their favorable balance of cost, efficiency, and stability.