Efficiency enhancement of light color conversion through surface plasmon coupling

Abstract

The efficiency enhancement of light color conversion from blue quantum well (QW) emission into red quantum dot (QD) emission through surface plasmon (SP) coupling by coating CdSe/ZnS QDs on the top of an InGaN/GaN QW light-emitting diode (LED) is demonstrated. Ag nanoparticles (NPs) are fabricated within a transparent conductive Ga-doped ZnO interlayer to induce localized surface plasmon (LSP) resonance for simultaneously coupling with the QWs and QDs. Such a coupling process generates three enhancement effects, including QW emission, QD absorption at the QW emission wavelength, and QD emission, leading to an overall enhancement effect of QD emission intensity. An Ag NP geometry for inducing an LSP resonance peak around the middle between the QW and QD emission wavelengths results in the optimized condition for maximizing QD emission enhancement. Internal quantum efficiency and photoluminescence (PL) decay time measurements are performed to show consistent results with LED performance characterizations, even though the QD absorption of PL excitation laser may mix with the SP-induced QD absorption enhancement effect in PL measurement.

Nanoantenna‐Enhanced Light‐Emitting Diodes: Fundamental and Recent Progress

“…b) Reproduced with permission. [ 72 ] Copyright 2018, Optical Society of America. c) Reproduced with permission.…”

“…In the same year, the researchers from the University of California reported a blue InGaN/GaN LED coupled with Ag nanoholes (Figure 4c), which shows that the decay rate of plasmonic‐coupled LED has been increased by 40 folds, realizing a high‐efficiency source as well as an ultrafast signal emitter. [ 72,73 ] LSPR can not only couple with excitons and drive the electron transfer of light‐emitting QWs, but also enhance the excitation rate, reduce the lifetime, and modulate the polarization of QDs in the color‐converting layer, improving the energy transfer from LED to QD layer and enhancing efficiency in multiple dimensions. [ 74 ] When QDs are used for light emission in the active region, by capping Au nanoparticles with QDs, designing nanoantenna's resonance wavelength matches the emission wavelength of QDs, the quantum efficiency reaches 60%.…”

Factors Affecting Surface Plasmon Coupling of Quantum Wells in Nitride-Based LEDs: A Review of the Recent Advances

“…C. H. Lin et al experimentally demonstrated the shift in SP resonance wavelength by annealing the Ag films of varying thicknesses at different temperatures [ 12 ]. The purpose was to tune the SP resonance wavelength to achieve resonance with emission wavelengths of QW and quantum dots (QDs) used in their studies.…”

“…( d ) Transmission spectra of the three AgNP structures shown in ( a – c ) illustrating the LSP resonances with peak wavelengths around 500, 540, and 580 nm. Reprinted with permission from [ 12 ]. Copyright 2018 The Optical Society.…”

“…The high-efficiency LEDs using this approach have the potential to replace the conventional lighting devices, but far more research is needed to realize high efficiency and cost-effective LEDs for practical applications. SPs serve various purposes in LEDs such as the enhancement of the emission efficiency, increasing the light extraction efficiency, the polarization of the emitted light, speed modulation, and increasing the color conversion efficiency [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”