Record-high efficiency in 1.54 µm electroluminescent diodes based on lead-free Cs3CrBr6: Er3+ semiconductor nanocrystals.

The realization of efficient 1.54 µm electroluminescence from erbium ions is persistently hampered by their intrinsically small absorption cross-section and low excitation efficiency in conventional hosts. This study addresses this by synthesizing lead-free Cs3CrBr6 perovskite nanocrystals. This material is a direct-bandgap n-type chromium-based halide semiconductor whose electronic structure provides good charge transport, serving as a suitable host for lanthanide doping. Er3+ incorporation serves as an efficient luminescent center and modulates the host's band structure. Leveraging the broadband absorption of Cr3+ for sensitization, combined with surface passivation, we achieve highly efficient Cr3+ to Er3+ energy transfer. This yields intense 1.54 µm emission with a photoluminescence quantum yield of 47%. The corresponding electroluminescent device attains a peak external quantum efficiency of 3.26%, among the highest values reported for solution-processed, Er3+-based near-infrared light-emitting diodes. This performance robustly validates the host's effectiveness in facilitating charge injection and transport. Consequently, this work provides a viable material strategy for high-performance 1.54 µm emission and lays a solid foundation for chromium-based halide perovskites in advanced optoelectronics.