An Eco‐Friendly Universal Strategy via Ribavirin to Achieve Highly Efficient and Stable Perovskite Solar Cells

The grain boundaries of perovskite films prepared by the solution method are highly disordered, with a large number of defects existing at the grain boundaries. These defect sites promote the decomposition of perovskite. Here, we use ribavirin obtained through bacillus subtilis fermentation to regulate the crystal growth of perovskite, inducing changes in the work function and energy level structure of perovskite, which significantly reduces the defect density. Based on density functional theory calculations, the defect formation energies of V I , V MA , V Pb , and Pb I in perovskite are improved. This increases the open‐circuit voltage of perovskite solar cells (PSCs) (ITO/PEDOT:PSS/perovskite/PCBM/BCP/Ag) from 1.077 to 1.151 V, and the power conversion efficiency (PCE) increases significantly from 17.05% to 19.86%. Unencapsulated PSCs were stored in the environment (humidity ≈35 ± 5%) for long‐term stability testing. After ≈900 h of storage, the PCE of the ribavirin‐based device retains 84.33% of its initial PCE, while the control‐based device retains only 13.44% of its initial PCE. The PCE of PSCs (ITO/SnO 2 /perovskite/Spiro‐OMETAD/Ag) is increased from 20.16% to 22.14%, demonstrating the universality of this doping method. This universal doping strategy provides a new approach for improving the efficiency and stability of PSCs using green molecular doping strategies.