Lead-Free CsMnCl ₃ Nanoparticles with Tunable Dual Fluorescence for Light-Emitting Applications

Lead halide perovskite (LHP) nanoparticles (NPs) have attracted significant attention due to their outstanding optical properties, positioning them as promising candidates for diverse optoelectronic applications. Nonetheless, the toxicity of lead and increasing regulatory restrictions pose considerable challenges. Consequently, numerous lead-free perovskite NP systems are being explored as potential alternatives. In this work, we introduce a characteristic cesium manganese chloride (CsMnCl3) NPs system exhibiting dual-color emission dependent on excitation energy. By meticulously optimizing synthesis conditions, we successfully achieved high phase purity in the hexagonal R3̅m structure, yielding distinct blue (451 nm) and red (669 nm) emissions. Advanced optical characterizations reveal controllable emission colors and intensities through precise tuning of exciton energies. Time-resolved photoluminescence (PL) studies confirm the self-trapped exciton (STE) origin of the red emission and reveal dynamic PL evolution between blue and red emissions within the initial 0–3 ns. Computational modeling based on a four-band energy diagram effectively elucidates the observed dual-emission behavior and the role of STEs within the electronic structure. Furthermore, CsMnCl3 NPs were successfully integrated into light-emitting diode (LED) devices, demonstrating their dual-color emission capabilities. The lead-free CsMnCl3 dual-emission perovskite system achieves a photoluminescence quantum yield of 33%, representing a promising candidate for low-toxicity, multicolor LEDs and optical sensors.