Crystallization and Morphology Tailoring via Functionalized Ligands for Efficient and Stable Perovskite Solar Cells

Overview

Perovskite solar cells have been regarded as one of the most promising alternatives to conventional polycrystalline silicon solar cells due to their excellent photovoltaic properties, flexibility, and relatively low cost. However, there is still a big gap in transitioning laboratory scale devices to industrial large area solar cell modules. Here, slot-die coating excels, mainly benefiting from its high compatibility with the industrial used roll -to-roll (R2R) method and low material cost. But, the enlarged device area makes the decomposition initiated by pinholes and defects more significant, largely affecting the performance of the devices. Most researchers limit their attention to regulating the crystallization process of perovskite film during the slot -die process. Therefore, defect passivation is often neglected because of extra surface coating processes, additional complexity, and costs. Hence, it is meaningful to find a strategy to modify the crystallization and suppress detrimental defects. Herein, it’s hypothesized that a long-chain ligand with fluorine groups can effectively tune the crystallization route and stabilize the surface of perovskite films. During crystallization, the fluoride group on the ligand which can coordinate with lead and the amine group will interact with the inorganic part of perovskite, thus modifying the crystallization process. Preliminary results show that incorporating 2 -(5′′′-fluoro-3′′′,4′- dimethyl-[2,2′:5′,2′′:5′′,2′′′-quaterthiophen]-5-yl) ethan -1-ammonium (F4T m) iodide can regulate the crystallization process and increase the grain sizes. As a result, the solar cell device performance and stability increases with the assistance of additive F4Tm. The results from the small-area devices show great potential of applying F4Tm ligand in slot-die printed perovskite solar cells.