Enhanced Operational Stability by Cavity Control of Single‐Layer Organic Light‐Emitting Diodes Based on Thermally Activated Delayed Fluorescence

Li, Yungui; Zee, Bas van der; Tan, Xin; Zhou, Xin; Wetzelaer, Gert‐Jan A. H.; Blom, Paul W. M.

doi:10.1002/adma.202304728

Cited by 8 publications

(2 citation statements)

References 51 publications

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“…2b . For single-layer OLEDs, changing the layer thickness modifies the optical cavity, while the recombination profile for any thickness can be simulated with the same set of charge transport parameters 10 , 32 . The experimental thickness-dependent EQE follows the same trend as the simulated optical outcoupling efficiency and is quantitatively well described when further considering the PLQY of the DMAC-BP neat film.…”

Section: Resultsmentioning

confidence: 99%

Inverted device architecture for high efficiency single-layer organic light-emitting diodes with imbalanced charge transport

Tan,

Dou,

Chua

et al. 2024

Nat Commun

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Many wide-gap organic semiconductors exhibit imbalanced electron and hole transport, therefore efficient organic light-emitting diodes require a multilayer architecture of electron- and hole-transport materials to confine charge recombination to the emissive layer. Here, we show that even for emitters with imbalanced charge transport, it is possible to obtain highly efficient single-layer organic light emitting diodes (OLEDs), without the need for additional charge-transport and blocking layers. For hole-dominated emitters, an inverted single-layer device architecture with ohmic bottom-electron and top-hole contacts moves the emission zone away from the metal top electrode, thereby more than doubling the optical outcoupling efficiency. Finally, a blue-emitting inverted single-layer OLED based on thermally activated delayed fluorescence is achieved, exhibiting a high external quantum efficiency of 19% with little roll-off at high brightness, demonstrating that balanced charge transport is not a prerequisite for highly efficient single-layer OLEDs.

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Section: Resultsmentioning

confidence: 99%

Inverted device architecture for high efficiency single-layer organic light-emitting diodes with imbalanced charge transport

Tan,

Dou,

Chua

et al. 2024

Nat Commun

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“…Given the balanced bipolar charge transport ability of 3,2‐PIC‐XT in neat film, non‐doped simplified OLEDs with thick 3,2‐PIC‐XT layers are proposed for the purpose of increasing exciton recombination zone and reducing exciton annihilation at the interfaces of functional layers as well as simplifying production of the device [69,70] . Such non‐doped thick‐layer devices are configured as ITO/MoO 3 (5 nm)/mCBP (10 nm)/3,2‐PIC‐XT (80 and 100 nm)/PPF (10 nm)/Liq (2 nm)/Al (Figure 5a), where the thick neat films of 3,2‐PIC‐XT function as EMLs and thin mCP and PPF layers serve as hole and electron injection layers, respectively.…”

Section: Resultsmentioning

confidence: 99%

Purely Organic Room‐Temperature Phosphorescence Molecule for High‐Performance Non‐Doped Organic Light‐Emitting Diodes

Peng,

Zou,

Zeng

et al. 2024

Angew Chem Int Ed

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Purely organic molecules with room‐temperature phosphorescence (RTP) are potential luminescent materials with high exciton utilization for organic light‐emitting diodes (OLEDs), but those exhibiting superb electroluminescence (EL) performances are rarely explored, mainly due to their long phosphorescence lifetimes. Herein, a robust purely organic RTP molecule, 3,6‐bis(5‐phenylindolo[3,2‐a]carbazol‐12(5H)‐yl)‐xanthen‐9‐one (3,2‐PIC‐XT), is developed. The neat film of 3,2‐PIC‐XT shows strong green RTP with a very short lifetime (2.9 μs) and a high photoluminescence quantum yield (72%), and behaviors balanced bipolar charge transport. The RTP nature of 3,2‐PIC‐XT is validated by steady‐state and transient absorption and emission spectroscopies, and the working mechanism is deciphered by theoretical simulation. Non‐doped multilayer OLEDs using thin neat films of 3,2‐PIC‐XT furnish an outstanding external quantum efficiency (EQE) of 24.91% with an extremely low roll‐off (1.6%) at 1000 cd m‒2. High‐performance non‐doped top‐emitting and tandem OLEDs are also achieved, providing remarkable EQEs of 24.53% and 42.50%, respectively. Delightfully, non‐doped simplified OLEDs employing thick neat films of 3,2‐PIC‐XT are also realized, furnishing an excellent EQE of 17.79% and greatly enhanced operational lifetime. The temperature‐dependent and transient EL spectroscopies demonstrate the electrophosphorescence attribute of 3,2‐PIC‐XT. These non‐doped OLEDs are the best devices based on purely organic RTP materials reported so far.

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Exploring Efficient Blue TADF Materials with Ultrafast Bipolar Charge Transport for High‐Efficiency Thick‐Layer OLEDs

Fu,

Liu,

Tang

et al. 2024

Adv Funct Materials

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Achieving strong solid‐state photoluminescence and fast charge transport simultaneously for organic molecules is of significant importance but challenging because of the trade‐off between these properties. Herein, two tailored blue luminescent molecules constructed with ring‐fused carbonyl‐containing electron acceptors and spiro‐acridine electron donors are developed. Owing to ordered long‐range molecular alignment with proper interaction energies, their neat films exhibit ultrafast bipolar charge transport and strong delayed fluorescence with high quantum yields and short lifetimes. In doped organic light‐emitting diodes (OLEDs), both molecules display eminent electroluminescence performances with excellent external quantum efficiencies (EQEs) of 40.6%. They also exhibit brilliant blue lights with record‐beating EQEs of 30.2% in non‐doped thin‐layer OLEDs, and more importantly, high‐performance simplified non‐doped thick‐layer OLEDs are achieved, rendering lowered driving voltages, and the best EQEs of 23.0% with tiny efficiency roll‐offs. In addition, using them as sensitizers, remarkable EQEs of 40.1% and 23.2% with ultrasmall efficiency roll‐offs are realized in blue hyperfluorescence thin‐layer and thick‐layer OLEDs, respectively. The operational lifetimes are obviously elongated matter in non‐doped thick‐layer devices or hyperfluorescence thick‐layer devices. This work provides promising candidates for efficient simplified thick‐layer OLEDs and opens a new avenue toward organic molecules with strong delayed fluorescence and fast charge transport simultaneously.

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Enhanced Operational Stability by Cavity Control of Single‐Layer Organic Light‐Emitting Diodes Based on Thermally Activated Delayed Fluorescence

Cited by 8 publications

References 51 publications

Inverted device architecture for high efficiency single-layer organic light-emitting diodes with imbalanced charge transport

Inverted device architecture for high efficiency single-layer organic light-emitting diodes with imbalanced charge transport

Purely Organic Room‐Temperature Phosphorescence Molecule for High‐Performance Non‐Doped Organic Light‐Emitting Diodes

Exploring Efficient Blue TADF Materials with Ultrafast Bipolar Charge Transport for High‐Efficiency Thick‐Layer OLEDs

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