Lead-free halide Cs2MnCl4:Cu+ as a new phosphor for efficient green light emission

Low-dimensional metal halides have attracted extensive attention because of their superior optoelectronic properties, high stability and structural diversity. In this work, we report a two-dimensional (2D) lead-free halide Cs2MnCl4:Cu+ as a new phosphor for white light-emitting diodes (LEDs). By doping copper(I) into manganese(II) sites, a strong green emission with a photoluminescence quantum yield (PLQY) of 70% was observed. The luminescence center was located at 530 nm and the optimal excitation wavelength was determined to be 310 nm, which suggests a large Stokes shift of 220 nm. Steady-state and transient fluorescence spectra show a decay time of 114.19 μs, indicating a self-trapped exciton (STE) emission mechanism which was further confirmed by temperature-dependent steady-state photoluminescence spectroscopy. This work suggests that manganese halides could be considered as a new family with high luminescence efficiency for optoelectronic applications.