Polymer‐Assisted Nucleation for Stable Single‐Crystal Perovskite Thin Films

Abstract Organic‐inorganic hybrid perovskite single crystals have emerged as a strong candidate in photovoltaic and general optoelectronic applications. However, the high supersaturation of the precursor solution leads to the rapid formation of a significant number of nuclei and a diminished concentration of perovskite solute. Consequently, the inadequate availability of precursors poses challenges in sustaining the subsequent crystal growth phase, culminating in the development of small‐sized single crystals. In this work, we report a controlled nucleation process to foster the growth of large‐size single crystals. This method through the coordination interaction between polyacrylic acid and Pb 2+ ions, and substitution of the coordination with I − ions. This reduces the formation of the Pb‐I 6 complex, which promptly emerges in a state of supersaturation and acts as a nucleus, thereby effectively reducing the number of nuclei formed. The single crystals produced using this method exhibit a lateral size exceeding 5 mm, an extended absorption range, a longer carrier lifetime of 10.93 ns, and enhanced stability. These crystals demonstrate the ability to remain stable even after storage in an ambient environment (T=20±5 °C, RH=60±5 %) for a period of 20 days.