Bridging the Green Gap: Monochromatic InP-Based Quantum-Dot-on-Chip LEDs with over 50% Color Conversion Efficiency

Abstract

Solid-state light-emitting diodes (LEDs) emit nearly monochromatic light, yet seamless tuning of emission color throughout the visible region remains elusive. Color-converting powder phosphors are therefore used for making LEDs with a bespoke emission spectrum, yet broad emission lines and low absorption coefficients compromise the formation of small-footprint monochromatic LEDs. Color conversion by quantum dots (QDs) can address these issues, but high-performance monochromatic LEDs made using QDs free of restricted, hazardous elements remain to be demonstrated. Here, we show green, amber, and red LEDs formed using InP-based QDs as on-chip color convertor for blue LEDs. Implementing QDs with near-unity photoluminescence efficiency yields a color conversion efficiency over 50% with little intensity roll-off and nearly complete blue light rejection. Moreover, as the conversion efficiency is mostly limited by package losses, we conclude that on-chip color conversion using InP-based QDs can provide spectrum-on-demand LEDs, including monochromatic LEDs that bridge the green gap.

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).…”

Near-Unity Photoluminescence Quantum Yield of Core-Only InP Quantum Dots via a Simple Postsynthetic InF3 Treatment

“…These qualities make QDs promising candidates for application in, e.g. , light-emitting diodes, photodetectors, biomedical imaging, lasers, and photovoltaics. − In particular, InP-based QDs are of commercial interest since the material is free of toxic and RoHS-restricted elements such as Cd and Pb. , …”

“… 1 − 13 In particular, InP-based QDs are of commercial interest since the material is free of toxic and RoHS-restricted elements such as Cd and Pb. 14 , 15 …”

Enhanced Surface Passivation of InP/ZnSe Quantum Dots by Zinc Acetate Exposure

“…Colloidal quantum dots (QDs) exhibit remarkable luminescent properties. Their ability to provide a precisely tuned and narrow emission line, alongside their compatibility for solution-based processing, has driven extensive research in photoluminescent color conversion and electroluminescence, for applications in display technologies, lighting systems, and energy devices. − Particularly, for visible light applications, cutting-edge technology demonstrators, including lasers and light emitting diodes (LEDs), have been successfully realized using Cd-based QDs. − However, in the past decade, the restriction on Cd imposed by the Restriction of Hazardous Substances Directive (RoHS) has redirected research interest toward indium phosphide (InP) as a nonrestricted alternative for visible light applications, where several recent results showcase the potential of InP-based QDs in LEDs based on electroluminescence and photoluminescent color conversion. ,− …”