Highly Monodisperse PbS Quantum Dots with Facet Engineering for High-Radiance Light-Emitting Diodes in the NIR-II Window

Solution-processed PbS quantum dot light-emitting diodes (QLEDs) with emission in the second near-infrared window (NIR-II, 1100–1700 nm) are excellent candidates as light sources for optical communication, night vision, and biomedical monitoring. However, it is still a tremendous challenge to achieve high-radiance PbS QLEDs due to serious QD surface traps and unbalanced charge injection. Herein, highly monodisperse PbS QDs with tailored facet growth were successfully synthesized by the continuous precursor injection method. The synthesized PbS QDs revealed a tunable absorption peak from 1200 to 1700 nm with a supernarrow full width at half-maximum (fwhm; <105 nm). The tailored surface facet growth effectively decreased the nonpolar (100) facet and surface defects. Furthermore, with a multilayered organic–inorganic hybrid architecture of indium tin oxide (ITO)/poly(ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS)/poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl))-diphenylamine) (TFB)/PbS QDs/ZnO/Al, the novel infrared PbS QLED exhibited an excellent maximum radiance of 16.14 W sr^–1 m^–2 at 6.15 V with a shortwave-infrared electroluminescence at ～1530 nm. Importantly, the NIR-II QLEDs using facet-tailored PbS QDs with the EL peak between 1100 and 1700 nm represented extremely high radiances. The excellent performances are ascribed to the passivated PbS QDs with a tailored surface facet and the hybrid device structure for charge injection balance. This work provides an effective approach for the preparation of high-quality PbS QDs and is expected to significantly boost the potential commercial applications of PbS NIR-II QLEDs.