Enhancing the optical characteristics of lead-free Cs3Cu2I5 films via phenethylammonium iodide

Lead-free copper-based halide perovskites, especially Cs₃Cu₂I₅, represent promising alternatives to toxic lead-based materials because of their excellent optoelectronic properties. However, their practical application is limited by challenges such as the need for strict inert-atmosphere processing and the presence of intrinsic defects. In this study, the ability of phenethylammonium iodide (PEAI) to improve the structural and morphological characteristics of Cs₃Cu₂I₅ films was explored, with the goal of enhancing their optical performance. A controlled ambient processing method was employed, in which PEAI at various concentrations was incorporated into the precursor solution. The results show that adding 1 mg of PEAI significantly improved the crystallinity, reduced the lattice strain, and increased the photoluminescence quantum yield (PLQY) from 68.8 % to 81.8 %, which corresponds to an absolute increase of 13 % compared with the control. Additionally, PEAI-treated films exhibit excellent stability, maintaining a PLQY of 81.5 % after 60 days of ambient storage. These findings highlight PEAI as a highly effective additive for optimizing copper-based halide perovskites, offering a straightforward path toward the development of efficient, stable, lead-free emitters for optical applications.