Low-dimensional phases engineering for improving the emission efficiency and stability of quasi-2D perovskite films

The two-dimensional (2D) Ruddlesden-Popper-type perovskites, possessing tunable bandgap, narrow light emission, strong quantum confinement effect, as well as a simple preparation method, are identified as a new generation of candidate materials for efficient light-emitting diodes. However, the preparation of high-quality quasi-2D perovskite films is still a challenge currently, such as the severe mixing of phases and a high density of defects within the films, impeding the further promotion of device performance. Here, we prepared the quasi-2D PEA₂MA_n-1Pb_nBr_3n+1 perovskite films by a modified spin-coating method, and the phases with large bandgap were effectively suppressed by the vacuum evaporation treatment. We systematically investigated the optical properties and stability of the optimized films, and the photoluminescence (PL) quantum yield of the treated films was enhanced from 23% to 45%. We also studied the emission mechanisms by temperature-dependent PL spectra. Moreover, the stability of films against moisture, ultraviolet light, and heat was also greatly improved.