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 I-2-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 I-2 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.