High-Radiance Shortwave Infrared Light-Emitting Diodes Based on Highly Stable PbS Colloidal Quantum Dots

Abstract

PbS quantum dot light-emitting diodes (QLEDs) emitting around 1550 nm promise important applications in optical communications. However, due to insufficient suppression of surface traps for large-size PbS quantum dots (QDs), their performance under large driving current density was not satisfactory. In this work, octanethiol surfactant was added into a PbS QD solution and adsorbed onto the dot surface. As a result, the surface traps and the continuous oxidation of the unprotected (100) facets in PbS QDs were greatly suppressed. Therefore, the PbS QDs with octanethiol doubled their photoluminescence efficiency and showed outstanding stability. The PbS-based QLEDs with benchmark device structure showed a breakthrough high radiance of 18.3 W sr–1 m–2 with >2000 mA/cm2 driving current density. The efficient passivation of surface traps with octanethiol surfactant and the suppressed coupling between excitons and surface states under large working current were the main reasons for achieving the breakthrough high radiance.

Pioneering method for the synthesis of lead sulfide (PbS) nanoparticles using a surfactant-free microemulsion scheme

“…Àt s Decay (9) where I 0 is the photocurrent, s Rise and s Decay are the rise and decay times, respectively, and t is the time constant. Fig.…”

“…1 PbS is a group IV-VI binary element with a low band gap, large exciton Bohr radius (18 nm), extreme quantum connement, high carrier mobility, low thermal conductivity, and other properties, which make strong quantization effects visible even for large particles or crystallites. 3 Hence, it is a promising candidate to play an active role in various optoelectronic devices, such as infrared photodetectors, 4 solar cells, [5][6][7][8] infrared light-emitting diodes (LEDs), 9 thermoelectric cells, 10 near-infrared light-emitting eld-effect transistors, 11 and llers in polymer nanocomposites, 12 and other elds such as telecommunications and biomedical applications. 3 Usually, chemical routes are preferred for the synthesis of nanostructures owing to the simplicity and availability of many controlling key parameters.…”

Advancements in semiconductor quantum dots: expanding frontiers in optoelectronics, analytical sensing, biomedicine, and catalysis

“…Since then, a great deal of strategic work has been done to increase the PLQY as in these early stages of synthetic technique development, CQDs suffered from a range of surface defects, which acted as traps for excitons and reduced the PLQY. These methods include core–shelling, 87–92 alloying, 93 alloy-shelling, 94,95 addition of foreign solvent or substrate, 96 ligand exchange or passivation 97–100 and ligand cleavage 101 etc. as described in Table 1 along with external quantum efficiency (EQE).…”

Solution-Phase Ligand Engineering for All-Quantum-Dot Near-Infrared Light-Emitting Diodes

“…To develop QD-based NIR-LEDs various material systems have been explored, namely lead chalcogenides (PbS, PbSe), , Ag 2 S, InAs and HgTe. , PbS QDs are at the forefront of the research in NIR-LED development due to their NIR tunable emission properties, high PLQY, long carrier lifetime, and resilience toward chemical and ambient degradation . NIR emitting narrow-bandgap PbS QDs dispersed in the matrix of large-bandgap PbS QD layer is an excellent architectural platform that results in the best-in-class performance in NIR-QD-LEDs. ,,, To date, all QD-based active layer (both matrix and emitter are from QDs of different bandgaps) based blend device structures have been realized using the solid-state layer-by-layer (LBL) ligand exchange approach.…”