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Engineering Efficiency Roll-Off in Organic Light-Emitting Devices

Erickson, Nicholas C. ; Holmes, Russell J.

Advanced functional materials, 2014-10, Vol.24 (38), p.6074-6080 [Periódico revisado por pares]

Blackwell Publishing Ltd

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  • Título:
    Engineering Efficiency Roll-Off in Organic Light-Emitting Devices
  • Autor: Erickson, Nicholas C. ; Holmes, Russell J.
  • Assuntos: Architecture ; Devices ; efficiency roll-off ; Excitation ; excitons ; Mathematical models ; OLEDs ; Organic light emitting diodes ; organic light-emitting devices ; organic semiconductors ; Pathways ; Quenching ; Reduction
  • É parte de: Advanced functional materials, 2014-10, Vol.24 (38), p.6074-6080
  • Notas: National Science Foundation (NSF) MRSEC Program - No. DMR-0819885
    ArticleID:ADFM201401009
    ark:/67375/WNG-TSZW4PLQ-Q
    University of Minnesota Initiative for Renewable Energy and the Environment
    istex:E07F720FE6F97C2BEA33B19227C67645AF0D042F
    ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: Previous studies have identified triplet‐triplet annihilation and triplet‐polaron quenching as the exciton density‐dependent mechanisms which give rise to the efficiency roll‐off observed in phosphorescent organic light‐emitting devices (OLEDs). In this work, these quenching processes are independently probed, and the impact of the exciton recombination zone width on the severity of quenching in various OLED architectures is examined directly. It is found that in devices employing a graded‐emissive layer (G‐EML) architecture the efficiency roll‐off is due to both triplet‐triplet annihilation and triplet‐polaron quenching, while in devices which employ a conventional double‐emissive layer (D‐EML) architecture, the roll‐off is dominated by triplet‐triplet annihilation. Overall, the efficiency roll‐off in G‐EML devices is found to be much less severe than in the D‐EML device. This result is well accounted for by the larger exciton recombination zone measured in G‐EML devices, which serves to reduce exciton density‐driven loss pathways at high excitation levels. Indeed, a predictive model of the device efficiency based on the quantitatively measured quenching parameters shows the role a large exciton recombination zone plays in mitigating the roll‐off. Engineering efficiency roll‐off in organic light‐emitting devices. The efficiency roll‐off in phosphorescent organic light‐emitting devices is investigated as a function of device architecture. The loss processes responsible for the roll‐off, namely triplet‐triplet annihilation and triplet‐polaron quenching, are found to depend strongly on device architecture and specifically, the spatial extent of the exciton recombination zone. Devices designed to have a broader recombination zone show a predictable reduction in the severity of the efficiency roll‐off.
  • Editor: Blackwell Publishing Ltd
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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