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Regardless of the impressive progress that perovskite solar cells (PSCs) have achieved, especially considering their power conversion efficiency (PCE) over 25%, traditional PSCs still contend with an inherent instability with...

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The p‐type dopant of spiro‐OMeTAD has been identified as a rational strategy for the enhancement of the hole transport ability in perovskite solar cells (PSCs). Herein, to enhance the conductivity and hole‐extraction ability of spiro‐OMeTAD, a low‐cost and facile method is developed by introducing iodine into the hole transport materials. Morphology observation, energy gap characterization, and photoelectrochemical measurements indicate that as a mild Lewis acid, oxidant, and p‐type dopant, iodine moderately oxidizes spiro‐OMeTAD, optimizes the energy match with perovskite, mitigates the trap state density, interface resistance, and carrier recombination, and improves the hole‐extraction ability and carrier transport capacity. Consequently, a planar PSC based on the spiro‐OMeTAD doped with 8 wt% iodine achieves a champion power conversion efficiency (PCE) of 19.69%. Conversely, the device with pristine spiro‐OMeTAD gets an efficiency of 18.04%. This work indicates a potential application of iodine as a promising p‐type dopant for spiro‐OMeTAD in PSCs.