Extremely efficient flexible organic light-emitting diodes with modified graphene anode

Han, Tae Hee; Lee, Youngbin; Choi, Myung Suk; Woo, Seong Hoon; Bae, Sang Hoon; Hong, Byung Hee; Ahn, Juhyeon; Lee, Tae Woo

doi:10.1038/nphoton.2011.318

Cited by 1,276 publications

(635 citation statements)

References 30 publications

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“…It exhibits many unusual physical properties, e.g., a rich magnetic quantization [1][2][3][4][5][6][7][8], half-integer Hall effect [9][10][11][12][13][14][15][16], high Young's modulus [17][18][19][20][21], high Fermi velocity (10 6 m/s), and others. Graphene could play an important role in technological applications such as electric circuits [22,23], field-effect transistors [24,25], light-emitting diodes [26][27][28], solar cells [29][30][31][32], and durable touch screens [33,34]. Due to the hexagonal symmetry with a rotational angle of 60 • , a non-doped graphene is a zero-gap semiconductor with a vanishing density of state at the Fermi level.…”

Section: Introductionmentioning

confidence: 99%

Configuration-enriched magneto-electronic spectra of AAB-stacked trilayer graphene

Lin

et al. 2015

Carbon

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We developed the generalized tight-binding model to study the magneto-electronic properties of AAB-stacked trilayer graphene. Three groups of Landau levels (LLs) are characterized by the dominating subenvelope function on distinct sublattices. Each LL group could be further divided into two sub-groups in which the wavefunctions are, respectively, localized at 2/6 (5/6) and 4/6 (1/6) of the total length of the enlarged unit cell. The unoccupied conduction and the occupied valence LLs in each subgroup behave similarly. For the first group, there exist certain important differences between the two sub-groups, including the LL energy spacings, quantum numbers, spatial distributions of the LL wavefunctions, and the field-dependent energy spectra.The LL crossings and anticrossings occur frequently in each sub-group during the variation of field strengths, which thus leads to the very complex energy spectra and the seriously distorted wavefunctions. Also, the density of states (DOS) exhibits rich symmetric peak structures. The predicted results could be directly examined by experimental measurements. The magnetic quantization is quite different among the AAB-, AAA-, ABA-, and ABC-stacked configurations.

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Section: Introductionmentioning

confidence: 99%

Configuration-enriched magneto-electronic spectra of AAB-stacked trilayer graphene

Lin

et al. 2015

Carbon

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“…However, the low WF (4.2-4.3 eV), very rough surface and very low surface coverage of silver nanowire networks essentially require additional thick buffer HIL to be used as transparent electrodes in organic light-emitting diodes (OLEDs) [17][18][19] and organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs). 20 Similarly, carbon-based materials such as carbon nanotubes 21,22 and graphene 4,[25][26][27] are also regarded as candidates for transparent electrodes because of their mechanical strength and flexibility, but they also have low WF (4.4-4.6 eV) and require an additional HIL. Therefore, a highly efficient flexible anode that has high WF should be developed to achieve high-performance simplified flexible optoelectronics at a low cost.…”

Section: Introductionmentioning

confidence: 99%

“…Previously, we have reported a high WF polymeric HIL called as GraHIL. 26 However, the GraHIL has very low conductivity (o10 − 3 S cm − 1 ), and requires essentially an additional conducting anode layer with high conductivity such as ITO and graphene. However, the AnoHIL acts as both anode and HIL and thus does not require an additional conductor, and can simplify the organic or organic-inorganic hybrid device structures including OLEDs and PeLEDs even with highly enhanced device performance.…”

Section: Introductionmentioning

confidence: 99%

Universal high work function flexible anode for simplified ITO-free organic and perovskite light-emitting diodes with ultra-high efficiency

et al. 2017

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Flexible transparent electrode materials such as conducting polymers, silver nanowires, carbon nanotubes and graphenes are being investigated as possible replacements for conventional brittle inorganic electrodes. However, they have critical drawbacks of low work function (WF), resulting in a high hole injection barrier to an overlying semiconducting layer in simplified organic or organic-inorganic hybrid perovskite light-emitting diodes (OLEDs or PeLEDs). Here, we report a new anode material (AnoHIL) that has multifunction of both an anode and a hole injection layer (HIL) as a single layer. The AnoHIL has easy WF tunability up to 5.8 eV and thus makes ohmic contact without any HIL. We applied our anodes to simplified OLEDs, resulting in very high efficiency (62% ph el − 1 for single and 88% ph el − 1 for tandem). The AnoHIL showed a similar tendency in simplified PeLEDs, implying universal applicability to various optoelectronics. We also demonstrated large-area flexible lightings using our anodes. Our results provide a significant step toward the next generation of high-performance simplified indium tin oxide (ITO)-free light-emitting diodes.

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“…[1][2][3][4][5][6][7][8] However, indium-tin oxide (ITO), the most widely used electrode in OLEDs, has a very poor tolerance to external mechanical stress. 9 Furthermore, its cost has increased gradually owing to a scarcity of indium.…”

Section: Introductionmentioning

confidence: 99%

“…9 In and Sn ions that diffuse from the ITO electrode to overlying layers can act as charge-trapping centers during the charge injection process, and this degrades the luminous efficiency and operational stability of organic opto-electronic devices owing to the exciton quenching effect of In and Sn atomic species. 6,9 Therefore, ITO-based electronic devices are unsuitable for practical flexible electronics. To enable the fabrication of flexible organic optoelectronic devices, the brittle ITO electrode should be replaced with a flexible transparent conducting electrode.…”

Section: Introductionmentioning

confidence: 99%

Approaching ultimate flexible organic light-emitting diodes using a graphene anode

et al. 2016

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Ultimate flexible organic light-emitting diodes (OLEDs) should have an ultra-high device efficiency, a low-efficiency roll-off at a high luminance and excellent flexibility. Here, we realized flexible tandem OLEDs using a graphene anode with a very high electroluminescent efficiency of~205.9 cd A − 1 , 45.2% (~396.4 cd A − 1 , 87.3% with a hemispherical lens) and a very low efficiency roll-off at a high luminance of~6.6% at 10 000 cd m − 2 (~3.8% with a hemispherical lens) by stacking two organic electroluminescence (EL) units. For the first time, we used an easily controlled and low-temperature processable charge generation layer with lithium nitride (Li 3 N). This simultaneously provided efficient stacking of EL units and enhanced compatibility of the flexible device on a thin plastic substrate. The flexible tandem OLEDs with a graphene anode also showed great flexibility against bending up to a bending strain of 6.7%. These results represent a significant advancement towards the production of next-generation flexible displays and solid-state lighting that use a graphene anode.

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Extremely efficient flexible organic light-emitting diodes with modified graphene anode

Cited by 1,276 publications

References 30 publications

Configuration-enriched magneto-electronic spectra of AAB-stacked trilayer graphene

Configuration-enriched magneto-electronic spectra of AAB-stacked trilayer graphene

Universal high work function flexible anode for simplified ITO-free organic and perovskite light-emitting diodes with ultra-high efficiency

Approaching ultimate flexible organic light-emitting diodes using a graphene anode

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