Yangyang Bian

High-quality InP-based quantum dots (QDs) have become very promising, environmentally benign light emitters for display applications, but their synthesis generally entails hazardous hydrofluoric acid. Here, we present a highly facile route to InP/ZnSe/ZnS core/shell/shell QDs with a near-unity photoluminescence quantum yield. As the key additive, the inorganic salt ZnF2 mildly reacts with carboxylic acid at a high temperature and in situ generates HF, which eliminates surface oxide impurities, thus facilitating epitaxial shell growth. The resulting InP/ZnSe/ZnS QDs exhibit a narrower emission line width and better thermal stability in comparison with QDs synthesized with hydrofluoric acid. Light-emitting diodes using large-sized InP/ZnSe/ZnS QDs without replacing original ligands achieve the highest peak external quantum efficiency of 22.2%, to the best of our knowledge, along with a maximum brightness of >110 000 cd/m2 and a T95 lifetime of >32 000 h at 100 cd/m2. This safe approach is anticipated to be applied for a wide range of III–V QDs.

Abstract To understand the exciton dynamics due to the electron delocalization in InP‐based quantum dot light‐emitting diodes (QLEDs), the exciton dynamics are systematically controlled in InP‐based QLEDs through varying the shell thicknesses of InP/ZnSe quantum dots (QDs) and the effective electrical field (E‐field) across the QDs. It is found that the field‐independent energy transfer is effectively suppressed as the shell thickness increases. However, InP/ZnSe QDs with thicker shells only have limited benefit for suppressing the exciton transfer due to field‐enhanced electron delocalization in films on electron transport layers or working devices. The field‐assisted exciton transfer is mainly driven by the large E‐field and field‐enhanced electron delocalization in InP/ZnSe QDs. External quantum efficiency of 22.56% is achieved in InP‐based QLEDs by reducing the effective E‐field (at 2 V bias). The breakthrough luminance of 136 090 cd/m −2 is achieved at a large bias of 7.2 V, due to the suppression of field‐enhanced electron delocalization by the ultra‐thick shell.

Indium phosphide (InP) is a representative of environmentally friendly quantum dots (QDs), and quantum dot light-emitting diodes (QLEDs) based on InP QDs are prime candidates for next-generation display applications. However, there are numerous nonradiative sites on the surface of InP QDs, which compromise the operational stability of QLEDs. Herein, we employed cysteamine (CTA) molecules for post-treatment of QD films, effectively passivating surface defects and nonradiative sites, thereby enhancing stability. This treatment enabled a long T95 lifetime of over 1,200 h at an initial luminance of 1,000 cd m–2. Additionally, CTA-treated QDs induced the formation of an interface dipole, elevating the energy levels of QDs and reducing the injection barrier for holes. Moreover, the dipole moment at the interface hindered electron injection, achieving a more balanced carrier injection in the device. Consequently, we achieved a peak external quantum efficiency (EQE) of 21.21%.

Abstract The external quantum efficiencies (EQE) and luminances of red InP‐based and blue ZnTeSe‐based quantum dot light‐emitting diodes (QLEDs) have exceeded 20% and 80 000 cd m −2 , respectively, and the T 50 @100 cd m −2 (time for the luminance decreasing by 50%) operational lifetime of red InP‐based QLEDs also have exceeded 1 000 000 h, nearing industrial application standards. However, the low EQE, luminance, and inferior lifetime of green InP‐based QLEDs restrict the application for their full‐color Cd‐free display and lighting applications. The large electron injection barrier and severe exciton quenching caused by defect states of ZnMgO (ZMO) nanoparticles (NPs) lead to lower electron concentration in the emitting layer, which results in reduced radiative recombination. Here, with the surface passivation of MgCl 2 , the exciton quenching sites are significantly suppressed, and the electron injection barrier is reduced owing to the conduction band minimum (CBM) levels upshift of ZMO. As a result, a high EQE of 21.43%, maximum luminance of 25 5985 cd m −2 , along with a long T 50 @1000 cd m −2 (over 4 600 h) and T 50 @100 cd m −2 (over 290 000 h) operational lifetime is achieved for green InP‐based QLEDs. These values have all exceeded the previous best values of green InP‐based QLEDs.