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Reduced graphene oxide enwrapped phosphors for long-term thermally stable phosphor converted white light emitting diodes

View Article: PubMed Central - PubMed

ABSTRACT

The long-term instability of the presently available best commercial phosphor-converted light-emitting diodes (pcLEDs) is the most serious obstacle for the realization of low-cost and energy-saving lighting applications. Emission from pcLEDs starts to degrade after approximately 200 h of operation because of thermal degradation of the phosphors. We propose a new strategy to overcome this thermal degradation problem of phosphors by wrapping the phosphor particles with reduced graphene oxide (rGO). Through the rGO wrapping, we have succeeded in controlling the thermal degradation of phosphors and improving the stability of fabricated pcLEDs. We have fabricated pcLEDs with long-term stability that maintain nearly 98% of their initial luminescence emission intensity even after 800 h of continuous operation at 85 °C and 85% relative humidity. The pcLEDs fabricated using SrBaSi2O2N2:Eu2+ phosphor particles wrapped with reduced graphene oxide are thermally stable because of enhanced heat dissipation that prevents the ionization of Eu2+ to Eu3+. We believe that this technique can be applied to other rare-earth doped phosphors for the realization of highly efficient and stable white LEDs.

No MeSH data available.


TEM and HRTEM images of GO 1350 from various regions.The corresponding SAED patterns are also shown in the inset.
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f3: TEM and HRTEM images of GO 1350 from various regions.The corresponding SAED patterns are also shown in the inset.

Mentions: Additional TEM/HRTEM images of GO 1350 phosphor samples are depicted in Fig. 3(a–d). In all the images, a contrast variation is observed at the edges of the images which are apparently rGO nanoscrolls wrapped over the phosphor particles. In order to confirm this, the diffraction patterns are recorded from the edges and the inner regions of the rGO wrapped phosphor particle. The SAED patterns are shown in the inset of Fig. 3(a–d) and corresponding regions from which the patterns are recorded, is also marked as red arrows. A clear difference in the diffraction patterns is observed for those recorded from the rGO (edges) as well as from the phosphor regions (inner region) of the rGO wrapped phosphor particles. The SAED pattern recorded from the inner regions correspond to the phosphor21 while the SAED pattern recorded from edges correspond to rGO222324.


Reduced graphene oxide enwrapped phosphors for long-term thermally stable phosphor converted white light emitting diodes
TEM and HRTEM images of GO 1350 from various regions.The corresponding SAED patterns are also shown in the inset.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037423&req=5

f3: TEM and HRTEM images of GO 1350 from various regions.The corresponding SAED patterns are also shown in the inset.
Mentions: Additional TEM/HRTEM images of GO 1350 phosphor samples are depicted in Fig. 3(a–d). In all the images, a contrast variation is observed at the edges of the images which are apparently rGO nanoscrolls wrapped over the phosphor particles. In order to confirm this, the diffraction patterns are recorded from the edges and the inner regions of the rGO wrapped phosphor particle. The SAED patterns are shown in the inset of Fig. 3(a–d) and corresponding regions from which the patterns are recorded, is also marked as red arrows. A clear difference in the diffraction patterns is observed for those recorded from the rGO (edges) as well as from the phosphor regions (inner region) of the rGO wrapped phosphor particles. The SAED pattern recorded from the inner regions correspond to the phosphor21 while the SAED pattern recorded from edges correspond to rGO222324.

View Article: PubMed Central - PubMed

ABSTRACT

The long-term instability of the presently available best commercial phosphor-converted light-emitting diodes (pcLEDs) is the most serious obstacle for the realization of low-cost and energy-saving lighting applications. Emission from pcLEDs starts to degrade after approximately 200 h of operation because of thermal degradation of the phosphors. We propose a new strategy to overcome this thermal degradation problem of phosphors by wrapping the phosphor particles with reduced graphene oxide (rGO). Through the rGO wrapping, we have succeeded in controlling the thermal degradation of phosphors and improving the stability of fabricated pcLEDs. We have fabricated pcLEDs with long-term stability that maintain nearly 98% of their initial luminescence emission intensity even after 800 h of continuous operation at 85 °C and 85% relative humidity. The pcLEDs fabricated using SrBaSi2O2N2:Eu2+ phosphor particles wrapped with reduced graphene oxide are thermally stable because of enhanced heat dissipation that prevents the ionization of Eu2+ to Eu3+. We believe that this technique can be applied to other rare-earth doped phosphors for the realization of highly efficient and stable white LEDs.

No MeSH data available.