Tuning the Shades of Red Emission in InP/ZnSe/ZnS Nanocrystals with Narrow Full Width for Fabrication of Light-Emitting Diodes

Abstract

While Cd-based luminescent nanocrystals (NCs) are the most mature NCs for fabricating efficient red light-emitting diodes (LEDs), their toxicity related limitation is inevitable, making it necessary to find a promising alternative. From this point of view, multishell-coated, red-emissive InP-based NCs are excellent luminescent nanomaterials for use as an emissive layer in electroluminescent (EL) devices. However, due to the presence of oxidation states, they suffer from a wide emission spectrum, which limits their performance. This study uses tris­(dimethyl­amino)­phosphine (3DMA-P) as a low-cost aminophosphine precursor and a double HF treatment to suggest an upscaled, cost-effective, and one-pot hot-injection synthesis of purely red-emissive InP-based NCs. The InP core structures were coated with thick layers of ZnSe and ZnS shells to prevent charge delocalization and to create a narrow size distribution. The purified NCs showed an intense emission signal as narrow as 43 nm across the entire red wavelength range (626–670 nm) with an emission quantum efficiency of 74% at 632 nm. The purified samples also showed an emission quantum efficiency of 60% for far-red wavelengths of 670 nm with a narrow full width of 50 nm. The samples showed a relatively long average emission lifetime of 50–70 ns with a biexponential decay profile. To demonstrate the practical ability of the prepared NCs in optoelectronics, we fabricated a red-emissive InP-based LEDs. The best-performing device showed an external quantum efficiency (EQE) of 1.16%, a luminance of 1039 cd m–2, and a current efficiency of 0.88 cd A–1.

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).…”

“…InP/ZnSe/ZnS CQDs were successfully used as the emissive layer in red-emissive LEDs, achieving an external quantum efficiency (EQE) of 1.16%, a luminance of 1039 cd m −2 , and a current efficiency of 0.88 cd A −1 . 89 In another study, monochromatic LEDs were developed using on-chip color conversion with InP-based InP/ZnSe/ZnS CQDs, achieving a consistent output spectrum approximately 45 nm wide. The CQDs, characterized by a near-unity PLQY, demonstrated a color conversion efficiency exceeding 50%, exhibiting minimal intensity roll-off and a wavelength shift at higher driving currents.…”