Exciton Self-Trapping Dynamics in 1D Perovskite Single Crystals: Effect of Quantum Tunnelling

We present experimental and theoretical investigations of the photophysics in the one-dimensional (1D) hybrid organic-inorganic perovskite (HOIP) white-light emitter, [DMEDA]PbBr₄. It is found that the broadband-emission nature of the 1D perovskite is similar to the case of two-dimensional (2D) HOIP materials, exciton self-trapping (ST) is the dominant mechanism. By comprehensive spectroscopic investigations, we observed direct evidence of exciton crossing the energy barrier separating free and ST states through quantum tunnelling. Moreover, we consider the lattice shrinking mechanisms at low temperatures and interpret the ST exciton formation process using a configuration coordinate diagram. We propose that the energy barrier separating free and ST excitons is temperature-dependent, and consequently, the manner of excitons crossing it is highly dependent on the exciting energy and temperature. For excitons located at the bottom of the free excitonic states, the quantum tunnelling is the dominant channel to the ST states.