Open-air-processed Perfluoro(4-methylpent-2-ene)-modified MAPbI3 solar cells actualize 21.25% PCE and excellent humidity stability

Open-air-processed perovskite solar cells (PSCs) already garnered significant attention of the international scholars because the uncomplicated and economically viable production methods. Nevertheless, the ambient atmosphere frequently poses a multitude of detrimental factors. For example, suboptimal levels of humidity and the presence of oxygen can result in flawed perovskite crystal formation and numerous surface imperfections, significantly diminishing the power conversion efficiency (PCE) and adversely affecting the final PSCs’ overall stability. Therefore, we employ an optimal approach utilizing liquid-phase small molecules to systematically optimize the perovskite layer, specifically incorporating the additive Perfluoro(4-methylpent-2-ene) (C₆F₁₂), into an environmentally benign anti-solvent for fabricating the MAPbI₃ layer. The C₆F₁₂ molecules, are liquid at room temperature, consist of carbon–carbon single or double bonds and carbon–fluorine bonds. Through Lewis acid-base interactions, the fluorine atoms within C₆F₁₂ can establish some covalent bonds with lead and methylamine, as well as form hydrogen bonds with methylamine. These bonding mechanisms proficiently address the vacancies created by iodine (V_I) within the perovskite framework. Meanwhile, the inherent hydrophobic properties of fluorine atoms provide improved moisture resistance to perovskite films produced in atmospheric conditions, thereby enhancing the resultant PSCs’ stabilization. Consequently, the upgrade perovskite layers demonstrate larger grain dimensions and diminished trap density. The optimal device, passivated with C₆F₁₂ and processed in air, achieves a champion PCE of 21.25%, approaching the performance of samples fabricated in a glove-box. Furthermore, the non-encapsulated device modified with C₆F₁₂ demonstrates exceptional stability across multiple variables. This straightforward and environmentally friendly approach is expected to broaden the applicability of PSCs.