Investigating the effects of carbon-based counter electrode layers on the efficiency of hole-transporter-free perovskite solar cells

Perovskite solar cells with organometal halides of inorganic-organic hybrid materials have been under investigation in the area of energy-conversion research and development. Among the various perovskite solar cells, the carbon-based hole-transporter-free type is a better option because of its low materials and manufacturing costs, availability, high efficiency, and long-term stability. In this study, carbon black (CB) and multiwall carbon nanotube (MWCNT) paste layers were prepared and applied to fluorine-doped tin oxide (FTO) conductive surfaces of the hole-transporter-free CH3NH3PbI3 perovskite solar cells as counter electrodes using the spin coating process. Cell performance studies were conducted on the prepared samples using a solar simulator. The effects of the current density-voltage (J-V) characteristics and hysteresis of perovskite solar cells of both CB- and MWCNT-based layers were evaluated in detail. It was determined that MWCNT-based solar cells have better short-circuit densities and possess higher power conversion efficiencies compared to CB paste-based solar cells. In both cases, the efficiencies of the carbon-based perovskite solar cells were considerably enhanced, which might be useful to improve the overall perovskite solar cell efficiencies.