Matching Solid-State to Solution-Phase Photoluminescence for Near-Unity Down-Conversion Efficiency Using Giant Quantum Dots

Abstract

Efficient, stable, and narrowband red-emitting fluorophores are needed as down-conversion materials for next-generation solid-state lighting that is both efficient and of high color quality. Semiconductor quantum dots (QDs) are nearly ideal color-shifting phosphors, but solution-phase efficiencies have not traditionally extended to the solid-state, with losses from both intrinsic and environmental effects. Here, we assess the impacts of temperature and flux on QD phosphor performance. By controlling QD core/shell structure, we realize near-unity down-conversion efficiency and enhanced operational stability. Furthermore, we show that a simple modification of the phosphor-coated light-emitting diode device-incorporation of a thin spacer layer-can afford reduced thermal or photon-flux quenching at high driving currents (>200 mA).

Alloyed Green-Emitting CdZnSeS/ZnS Quantum Dots with Dense Protective Layers for Stable Lighting and Display Applications

“…Quantum dots (QDs) have demonstrated great potential as light converters in lighting and display applications owing to their narrow conduction band, high quantum efficiency, color tunability, and high color purity. − Regarding the solid-state lighting materials for obtaining white light, QDs can afford an adequate color space, high color rendering index, and wider color gamut than conventional yttrium aluminum garnet phosphor in white light-emitting diodes (WLEDs). − …”

Coordination-induced emission enhancement in gold-nanoclusters with solid-state quantum yields up to 40% for eco-friendly, low-reabsorption nano-phosphors

“…When the converted light suffer from the reabsorption effect, the light intensity can be reduced accompanied with spectral red-shift, which would degrade the performance of light-conversion phosphors. Unfortunately, most of CQDs have small Stokes shift, leading to severe reabsorption losses 15,16 . To address this problem, several strategies have been applied to enlarge Stokes shift by separating the absorbing and emitting states, for example, designing heterostructured core/shell CQDs or doped CQDs 5–7 .…”

Twist Angle-Dependent Interlayer Exciton Lifetimes in van der Waals Heterostructures

“…Using a rate equation analysis for a three-level system (see SM for details, which includes Refs. [45][46][47][48]), we attribute the fast (slow) decay component to the lifetime of the bright (dark) exciton assuming the scattering rate between the bright and dark state is slower than the bright exciton lifetime. In all samples, we observe shorter IX lifetimes as the energy of the resonance increases as shown in the inset to each panel in Figs.…”