Phase-regulated energy funneling and carrier relaxation dynamics in quasi-2D perovskites revealed by micro-area transient absorption spectroscopy.

Two-dimensional (2D) perovskites have attracted considerable attention as promising candidates for optoelectronic devices due to their excellent optical properties, structural tunability, and intrinsic quantum well architectures. Understanding how phase composition regulates ultrafast carrier dynamics is essential for optimizing device performance. In this work, monocrystalline thin films of (PEA)2(MA)n-1PbnI3n+1 with well-controlled phase distributions were prepared using a space-confined anti-solvent crystallization method. Micro-area femtosecond pump-probe spectroscopy was employed to investigate the influence of phase composition on the relaxation behavior of photoexcited carriers. The results reveal that increasing the proportion of small-n phases leads to a pronounced extension of the excited-state relaxation process in large-n domains, attributed to suppressed defect-assisted trapping and enhanced interphase carrier transfer efficiency. This study provides a microscopic physical picture of the energy funneling mechanism governed by phase composition in quasi-2D perovskites and establishes an experimental framework for regulating carrier dynamics.