Defect Engineering in 2D Perovskite by Mn(II) Doping for Light-Emitting Applications

Low-dimensional perovskites are considered good candidates for light-emitting applications given their high exciton binding energy. Yet, single-layered two-dimensional (2D) perovskites are strongly limited by trap-assisted recombination and suffer from low luminescence yields, hampering their application in electroluminescence devices. Here, we use synthetic and defect engineering strategies to overcome such issues. We employ metallic doping (Mn2+ and Eu3+) to introduce luminescent impurities in the 2D perovskite NMA2PbX4 (NMA = 1-naphtylmethylammonium). By means of temperature-dependent and time-resolved spectroscopy, we demonstrate efficient energy transfer to Mn2+ centers. This avoids funneling of photo-excited species in inefficient recombination channels, enhancing photoluminescence and giving a quantum yield surpassing 20% in doped films. Eventually, we embody Mn-doped NMA2PbBr4 in a light-emitting diode architecture and show electroluminescence from the Mn2+ 4T1 → 6A1 transition. This proof-of-concept demonstration shows the potential of doping in layered perovskites and prompts the study of a wider range of host-guest structures. Metal halide perovskites have emerged for light-emitting applications, such as light-emitting diodes (LEDs). While intensive research has focused on three-dimensional (3D) perovskites, layered perovskites are also gaining interest for their peculiar light-emitting properties. The higher exciton binding energy of low-dimensional perovskites is considered beneficial to improve the radiative recombination efficiency. However, the luminescence yield of single-layered two-dimensional (2D) perovskites is severely lowered by trap-assisted recombination. By including Mn2+ and Eu3+ in a 2D perovskite, we show that metallic doping can be exploited to enhance and tune its luminescence. Efficient energy transfer from the perovskite to the dopant is achieved, provided that a suitable energy level alignment of the host-guest system is realized. We show that such a mechanism can be exploited to tune the material's electroluminescence in a proof-of-concept LED based on a Mn-doped 2D perovskite. Cortecchia et al. report the use of metallic dopants to overcome the detrimental trap-mediated non-radiative recombination processes, lowering the luminescence yield in two-dimensional perovskites. This results in tuning and enhancement of the perovskite's luminescence properties. In particular, efficient energy transfer and high luminescence yield are obtained with manganese doping. This strategy is shown to be suitable for application in light-emitting diodes.