Efficient Perovskite Solar Cells with Iodine‐Doped Spiro‐OMeTAD Hole Transport Layer via Fast Oxidation

The state‐of‐the‐art perovskite solar cells (PSCs) have reached a certified efficiency approaching 26% in decades. It is noteworthy that the record efficiencies are almost based on the regular structure PSCs using spiro‐OMeTAD (Spiro) as the hole transport layer. However, the necessity of rather long (8–24 h) oxidation process of Spiro can probably cause potential instability and poor reproducibility of PSCs because of the hygroscopic additives in Spiro and humid‐sensitive perovskite layer underneath. Herein, a fast oxidation method of Spiro by introducing the iodine molecule as oxidant dopant is demonstrated , which can enhance the conductivity and hole‐extraction ability of the Spiro film in extremely short time, even without oxygen exposure. The I2‐doped Spiro‐based devices reach optimal efficiencies of 25.44% and 24.27% under short oxidation (4 h) and oxygen‐free environment, respectively. In addition, the I2 helps Spiro keep a durable oxidized‐state, making Spiro layer qualified conductivity for improved stability of PSCs. Consequently, the oxygen‐free oxidized Spiro‐based target champion device remains the 97.8% of initial steady output after storage of 30 days.