CNTs/Cf based counter electrode for highly efficient hole-transport-material-free perovskite solar cells

[Display omitted] •A CNTs/Cf CE was used as counter electrode (CE) in PSCs for the first time.•The CNTs/Cf CE exhibited high-efficiency hole extraction ability and fast hole transfer performance.•PSC based on CNTs/Cf CE exhibits high power conversion efficiency of 11.80 %. A carbon nanotubes (CNTs)/carbon fiber (Cf) has been prepared and used as a counter electrode (CE) for hole-transport-material-free perovskite solar cells (PSCs). It was found that CNTs/Cf material effectively increased the contact area between perovskite and carbon layer, correspondingly decreased the charge exchange resistance and enhanced hole extraction ability at perovskite/CE interface. In addition, hole transfer in CNTs/Cf CE was accelerated due to the existence of “highway” hole transfer path derived from CNTs/Cf structure, which reduced photoluminescence peak intensity. As a result, the PSC based on CNTs/Cf CE with high-efficiency hole extraction ability and fast hole transfer performance had a high power conversion efficiency (PCE) of 11.80 % compared with that of CNTs CE (8.93 %) and Cf CE (7.47 %).