Potassium Methacrylate Additive Strategy for Improved Stability of Ultrathin Copper‐Based Perovskite Solar Cells

Abstract Perovskite solar cell (PSC) using ultrathin metal transparent electrode is a promising power source for wearable electronics and aerospace applications. However, the environmental stability of device is challenging, due to the undesirable interdiffusion of metal and halogen ions. In this work, PSCs are constructed by using ultrathin copper (Cu) electrodes with low reactivity, combined with potassium methacrylate (KMMA) additive. On one hand, carbonyl groups in KMMA interact with the perovskite and improve quality of perovskite films. As a result, the power conversion efficiency (PCE) of ultrathin Cu‐based PSC is increased from 12.49% to 14.72%. On the other hand, benefitting from the binding of K⁺ with halogen ion, the interdiffusion of Cu and I ions is hindered. Thus, PSCs retain 80% and 75% of the initial PCE under heating at 85 °C for 130 h and maximum power point for 300 h, respectively. To the best of the knowledge, it is one of the best thermal and operational stability for the PSCs using metal‐based electrodes. At last, the symmetric PSCs exhibit superior folding stability which maintain 85.3% of initial PCE after folding for 500 cycles. Foldable PSCs on ultrathin Cu electrodes with excellent stability are attractive power sources in wearable applications.