Broadband Emission-Enabled Energy Transfer in Double Perovskites for Efficient Er3+-Driven Long-Wavelength Near-Infrared Optoelectronics

High-efficiency near-infrared (NIR) light-emitting diodes (LEDs) operating in 800-2000 nm spectral window are pivotal for advancing optical communication, biomedical imaging, and security sensing. Here, a strategy using double perovskite Cs 2 AgInCl 6 nanocrystals co-doped with Bi 3+ , Yb 3+ , and heavily doped Er 3+ is demonstrated to achieve efficient long-wavelength NIR emission. The double perovskite host with self-trapped excitons (STEs) property serves as an energy reservoir for subsequent transfer to Er 3+ . Bi 3+ doping induces lattice distortion, enhancing STEs formation and breaking octahedral symmetry around Er 3+ to boost the 4 I 13/2 → 4 I 15/2 transition. Yb 3+ as a sensitizer, bridges the energy gap between STEs and Er 3+ , facilitating efficient energy transfer to populate Er 3+ metastable states. This synergistic mechanism, enabled by double perovskite's broadband emission and homovalent doping tolerance, allows heavy Er 3+ loading (≥20% molar-ratio), driving a photoluminescence quantum yield of 31% at 1540 nm. NIR LEDs fabricated with these nanocrystals achieve a champion external quantum efficiency (EQE) of 1.79% at 1540 nm (average EQE: 1.49%) and maintain 50% emission intensity for 3.3 h under continuous operation. This work establishes double perovskites as a versatile platform for STEs-mediated NIR emission, offering a new paradigm for designing high-performance long-wavelength optoelectronic devices.