Unveiling the Intrinsic Photophysics in Quasi-2D Perovskites

Abstract The 2D perovskites have drawn intensive attentions due to their unique stability and outstanding optoelectronic properties. However, the debate surrounding the spatial phase distribution and band alignment among different 2D phases in the quasi-2D perovskite has created complexities in understanding the carrier dynamics, hindering material and device development. In this study, we employed highly sensitive transient absoprtion spectroscopy to investigate the carrier dynamics of (BA)2(MA)n−1PbnI3n+1 quasi-2D Ruddlesden-Popper (RP) perovskite thin film, nominally prepared as n = 4. We observed the carrier density dependent electron and hole transfer dynamics between 2D and 3D phases. Under low carrier density within the linear response range, we successfully resolved three ultrafast processes of both electron and hole transfers, spanning from hundreds of fs to several ps, tens to hundreds of ps, and hundreds of ps to several ns, which can be attributed to lateral-epitaxial, partial-epitaxial and disordered-interface heterostructures between 2D and 3D phases. By considering the interplay among phase structure, band alignment and carrier dynamics, we have proposed material synthesis strategies aimed at enhancing the carrier transport. Our results not only provide deep insights into an accurate intrinsic photophysics of quasi-2D perovskites, but also inspire advancements in the practical application of these materials.