Self‐Organized Co3O4‐SrCO3 Percolative Composites Enabling Nanosized Hole Transport Pathways for Perovskite Solar Cells

Perovskite solar cells (PSCs) are expected to profoundly impact the photovoltaic society on account of its high‐efficiency and cost‐saving manufacture. As a key component in efficient PSCs, the hole transport layer (HTL) can selectively collect photogenerated carriers from perovskite absorbers and prevent the charge recombination at interfaces. However, the mainstream organic HTLs generally require multi‐step synthesis and hygroscopic dopants that significantly limit the practical application of PSCs. Here, a self‐organized percolative architecture composed of narrow bandgap oxides (e.g., Co3O4, NiO, CuO, Fe2O3, and MnO2) and wide bandgap SrCO3 oxysalt as efficient HTLs for PSCs is presented. The percolation of dual phases offers nanosized hole transport pathways and optimized interfacial band alignments, enabling significantly improved charge collection compared with the single phase HTLs. As a consequence, the power conversion efficiency boosted from 8.08% of SrCO3 based device and 15.47% of Co3O4 based device to 21.84% of Co3O4‐SrCO3 based one without notable hysteresis. The work offers a new direction by employing percolative materials for efficient charge transport and collection in PSCs, and would be applicable to a wide range of opto‐electronic thin film devices. A percolative architecture of a Co3O4‐SrCO3 composite is applied as an efficient hole transport layer (HTL) for perovskite solar cells. The percolation of the dual phases offers nanosized hole transport pathways and optimized interfacial band alignments, enabling significantly improved charge collection compared with the single phase HTLs, leading to excellent photovoltaic performance.