Toward High-Efficiency Near-Infrared LEDs through Fluorocytosine-Doped Tin–Lead Halide Perovskites

High Resolution Image Download MS PowerPoint Slide Perovskite light-emitting diodes (Pev-LEDs) have attracted increasing interest due to their high quantum efficiency, excellent spectral tunability, and low-cost solution processability. In particular, near-infrared (NIR) emission beyond 900 nm is highly desirable for applications in biomedical imaging, night vision, and optical sensing; however, achieving high radiance and device stability at wavelengths above 950 nm remains challenging. Mixed lead–tin halide perovskites provide an effective route to extend Pev-LEDs into the NIR region, yet their performance is often limited by poor film quality and nonradiative recombination. Here, we systematically investigate the structural, optical, and electroluminescent properties of pure Pb-based FA 0.6 MA 0.3 Cs 0.1 PbI 3 and mixed Pb–Sn (FA 0.6 MA 0.3 Cs 0.1 Pb 0.5 Sn 0.5 I 3 ) perovskites for NIR Pev-LEDs. While the mixed Pb–Sn device exhibits NIR emission with an external quantum efficiency (EQE) of 1.12%, the incorporation of 5-fluorocytosine (5-FC) significantly improves film crystallinity and morphology, leading to enhanced carrier recombination. Consequently, the optimized device delivers an improved EQE of 1.60% with stable electroluminescence centered at 1035 nm, highlighting the effectiveness of 5-FC in advancing high-performance Pb–Sn perovskite NIR LEDs.