Cross-stacked superaligned carbon nanotube electrodes for efficient hole conductor-free perovskite solar cells

Cross-stacked superaligned carbon nanotube (CSCNT) sheets drawn from CNT arrays with excellent conductivity, porosity and flexibility are used as low-cost back contacts for hole conductor-free mesoscopic CH3NH3PbI3/TiO2 heterojunction perovskite solar cells (PSCs). PSCs integrated with CSCNTs achieve a power conversion efficiency of up to 8.65% and over 10.54% by further doping the CSCNTs with iodine. Moreover, PSCs encapsulated with a layer of polymer poly(methylmethacrylate) exhibit outstanding stability in the dark and under illumination. This work represents a significant step toward the commercialization of the low-cost, stable and high-efficiency hole conductor-free PSCs.