2-Fluoroethylamine Hydrochloride Additive for High-Efficient and Stable Fapbi3 Perovskite Solar Cells

Abstract

In the pursuit of high-efficiency perovskite solar cells (PSCs) based on α-phase formamidine lead iodide (FAPbI3), the addition of methyl ammonium chloride (MACl) to the precursor solution has been a common practice, as it serves to improve phase stability, grain size, and crystallinity. Nevertheless, the instability of MA within the perovskite framework poses a significant constraint on the long-term stability of the device. To address this concern, we opted to introduce 2-fluoroethyl-1-amine hydrochloride (FEACl) to FAPbI3 in lieu of MACl. Our research findings demonstrate that upon the incorporation of FEACl, it can interact with perovskite precursors to promote the growth of perovskite crystals and strengthen the α-FAPbI3. Moreover, the large cations are still not incorporated into the lattice, which minimizes the change in the band gap of FAPbI3. Therefore, the photovoltaic performance and stability of perovskite solar cells have been improved. The best-performing devices have a power conversion efficiency (PCE) of 24.30% and a fill factor (FF) of 84.37%. When unpackaged devices are stored at room temperature with a relative humidity of 20% - 35% for 1000 hours, the efficiency remains 83.57% of the initial value.

Keywords: passivation defects, high efficiency, perovskite solar cells, 2-fluoroethylamine hydrochloride, stability