Identifying self-trapped excitons in 2D perovskites by Raman spectroscopy [Invited]

Two-dimensional (2D) perovskites exhibit broadband emission due to strong exciton–phonon coupling-induced self-trapped excitons and thus would find important applications in the field of white-light emitting devices. However, the available identifying methods for self-trapped excitons are currently rather limited and complex. Here, we identify the existence of self-trapped excitons by Raman spectroscopy in both excited and non-excited states. Under excited states, the shifting of the Raman peak indicates the presence of the lattice distortion, which together with the extra Raman scattering peak reveals the presence of self-trapped excitons. Our work provides an alternative simple method to study self-trapped excitons in 2D perovskites.