Efficient and Bright Deep‐Red Light‐Emitting Diodes based on a Lateral 0D/3D Perovskite Heterostructure

Abstract Bright and efficient deep‐red light‐emitting diodes (LEDs) are important for applications in medical therapy and biological imaging due to the high penetration of deep‐red photons into human tissues. Metal‐halide perovskites have potential to achieve bright and efficient electroluminescence due to their favorable optoelectronic properties. However, efficient and bright perovskite‐based deep‐red LEDs have not been achieved yet, due to either Auger recombination in low‐dimensional perovskites or trap‐assisted nonradiative recombination in 3D perovskites. Here, a lateral Cs 4 PbI 6 /FA x Cs 1− x PbI 3 (0D/3D) heterostructure that can enable efficient deep‐red perovskite LEDs at very high brightness is demonstrated. The Cs 4 PbI 6 can facilitate the growth of low‐defect FA x Cs 1− x PbI 3 , and act as low‐refractive‐index grids, which can simultaneously reduce nonradiative recombination and enhance light extraction. This device reaches a peak external quantum efficiency of 21.0% at a photon flux of 1.75 × 10 21 m −2 s −1 , which is almost two orders of magnitude higher than that of reported high‐efficiency deep‐red perovskite LEDs. Theses LEDs are suitable for pulse oximeters, showing an error <2% of blood oxygen saturation compared with commercial oximeters.