Low Temperature, Vacuum‐processed Bismuth Triiodide Solar Cells with Organic Small‐molecule Hole Transport Bilayer

Herein, the preparation of fully vacuum‐processed bismuth triiodide solar cells with low annealing temperature is reported. Planar n‐i‐p devices are prepared using a thin compact SnO2 layer as the electron extraction layer and an electron blocking/hole extraction bilayer consisting of an intrinsic and doped organic hole‐transport molecule. Using this configuration, herein, higher fill‐factors and overall power conversion efficiencies than with conventional solution‐processed hole transport materials are achieved.