Grain Engineering for Highly-Efficient Near-Infrared Perovskite Light-Emitting Diodes

Metal halide perovskites have shown great potential for next-generation light-emitting diodes (LEDs). Notably, near-infrared (NIR) perovskite LEDs (PeLEDs) typically outperform their organic and quantum-dot counterparts. However, their performance still falls short of the high-performing but costly epitaxial III-V semiconductor devices, which generally exceed 30% in external quantum efficiency (EQE) with very high brightness. Enhancing the performance of PeLEDs requires a deeper understanding and control of grain growth and nanoscale morphology.<br/>In this study, we present a comprehensive grain engineering methodology that incorporates two complementary and synergistic approaches to improve outcoupling efficiency and promote defect passivation. Through a solvent engineering technique, we achieved exceptional control over perovskite grain size and spatial distribution, leading to a significant increase in light-outcoupling efficiency to approximately 40%. Additionally, by creating 2D/3D heterostructures with a conjugated cation, we observed reduced defect densities and faster radiative recombination rates.<br/>As a result, the NIR PeLEDs demonstrated a peak EQE of 29.0% at a high current density of 183 mA/cm². An average EQE of 26.3% was obtained across 40 devices, with independent cross-validation across institutions. These devices also exhibited extremely high brightness, with a maximum radiance of 929 W/sr m². These findings indicate a promising future for PeLEDs as a low-cost, high-performance NIR light source for practical applications.