Eliminating Hole Extraction Barrier in 1D/3D Perovskite Heterojunction for Efficient and Stable Carbon‐Based CsPbI 3 Solar Cells with a Record Efficiency

Carbon‐based perovskite solar cells (C‐PSCs) have the advantages of low‐cost and high‐stability, but their photovoltaic performance is limited by severe defect‐induced recombination and low hole extraction efficiency. 1D perovskite is proven to effectively passivate the defects on the perovskite surface, therefore reducing non‐radiative recombination loss. However, the unsuitable energy level of most 1D perovskite renders an undesired downward band bending for 3D perovskite, resulting in a high hole extraction barrier and reduced hole extraction efficiency. Therefore, rational design and selection of 1D perovskites as the modifiers are essential in balancing defect passivation and hole extraction. In this work, based on simulation calculations, thiocholine iodide (TchI) is selected to prepare 1D perovskite with high work function and then constructs TchPbI 3 /CsPbI 3 1D/3D perovskite heterojunction. Experimental results show that this strategy eliminates the hole extraction barrier at the perovskite/carbon interface, which improves the hole extraction efficiency of corresponding devices. Meanwhile, the strong interaction between the thiol group and Pb suppresses defect‐induced recombination effectively and improves the stability of CsPbI 3 . The assembled C‐PSCs exhibit a champion efficiency of 19.08% and a certified efficiency of 18.7%. To the best of the knowledge, this is a new efficiency record for inorganic C‐PSCs.