Ultralow-voltage Auger-electron-stimulated organic light-emitting diodes

He, Shou-Jie; Lu, Zheng‐Hong

doi:10.1117/1.jpe.6.036001

Cited by 13 publications

(9 citation statements)

References 57 publications

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“…Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) values for rubrene and C 60 taken from refs. 6, 7, 10, 51 , BCP values taken from refs. 18, 19 .…”

Section: Resultsmentioning

confidence: 99%

“…One of the most commonly studied devices uses the small-molecule rubrene as emitter and hole transporter and the fullerene C 60 as the electron transporter. In these devices, two distinct mechanisms have been proposed for the low-voltage EL: an Auger-assisted energy up-conversion process at the heterojunction interface 6,7 , or Dexter transfer of triplet charge transfer (CT) states into triplet exciton states, followed by TTA to produce an emitting singlet 8–10 . In both cases, the non-linear charge dynamics at the rubrene/C 60 interface are crucial to the mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Higher order effects in organic LEDs with sub-bandgap turn-on

et al. 2019

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Spin-dependent nonlinear processes in organic materials such as singlet-fission and triplet-triplet annihilation could increase the performance for photovoltaics, detectors, and light emitting diodes. Rubrene/C60 light emitting diodes exhibit a distinct low voltage (half-bandgap) threshold for emission. Two origins for the low voltage turn-on have been proposed: (i) Auger assisted energy up-conversion, and (ii) triplet-triplet annihilation. We test these proposals by systematically altering the rubrene/C60 interface kinetics by introducing thin interlayers. Quantitative analysis of the unmodified rubrene/C60 device suggests that higher order processes can be ruled out as the origin of the sub-bandgap turn-on. Rather, band-to-band recombination is the most likely radiative recombination process. However, insertion of a bathocuproine layer yields a 3-fold increase in luminance compared to the unmodified device. This indicates that suppression of parasitic interface processes by judicious modification of the interface allows a triplet-triplet annihilation channel to be observed.

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“…Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) values for rubrene and C 60 taken from refs. 6, 7, 10, 51 , BCP values taken from refs. 18, 19 .…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Higher order effects in organic LEDs with sub-bandgap turn-on

et al. 2019

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“…Both turn‐on voltages are lower than the emission photon energy of 2.3 eV. Recombination via defect states, thermionic emission, and Auger‐assisted energy up conversion are considered as potential mechanisms for subgap EL . If recombination via defect states is responsible for the subgap EL, the emission peak of EL spectrum at subbandgap voltage should red‐shift, because the defect state is lower than 2.3 eV .…”

Section: Device Performances Of Pure Fapbbr3‐based Peleds With Diffmentioning

confidence: 99%

“…The most likely mechanism for subbandgap turn‐on voltage is efficient Auger‐assisted energy up‐conversion process at the PEDOT:PSS/FAPbBr 3 interface, as schematically illustrated in Figure b. Under forward bias, the holes accumulate at the PEDOT:PSS/FAPbBr 3 interface because of the energy barrier, i.e., 1.02 eV for 4083 device and 0.72 eV for 8000 device.…”

Section: Device Performances Of Pure Fapbbr3‐based Peleds With Diffmentioning

confidence: 99%

All‐Solution‐Processed Pure Formamidinium‐Based Perovskite Light‐Emitting Diodes

Wang

Song

et al. 2018

Advanced Materials

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All-solution-processed pure formamidinium-based perovskite light-emitting diodes (PeLEDs) with record performance are successfully realized. It is found that the FAPbBr device is hole dominant. To achieve charge carrier balance, on the anode side, PEDOT:PSS 8000 is employed as the hole injection layer, replacing PEDOT:PSS 4083 to suppress the hole current. On the cathode side, the solution-processed ZnO nanoparticle (NP) is used as the electron injection layer in regular PeLEDs to improve the electron current. With the smallest ZnO NPs (2.9 nm) as electron injection layer (EIL), the solution-processed PeLED exhibits a highest forward viewing power efficiency of 22.3 lm W , a peak current efficiency of 21.3 cd A , and an external quantum efficiency of 4.66%. The maximum brightness reaches a record 1.09 × 10 cd m . A record lifetime T of 436 s is achieved at the initial brightness of 10 000 cd m . Not only do PEDOT:PSS 8000 HIL and ZnO NPs EIL modulate the injected charge carriers to reach charge balance, but also they prevent the exciton quenching at the interface between the charge injection layer and the light emission layer. The subbandgap turn-on voltage is attributed to Auger-assisted energy up-conversion process.

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“…As typical organic semiconducting materials, the rubrene possesses large mobility and has lately attracted much research interest due to its low-threshold injection characteristics in heterojunction devices [36][37][38][39][40]. In this work, by embedding the classical Poisson's equation into the standard SH algorithm, the non-adiabatic dynamics of the charge injection at the metal/organic interfaces is investigated within the framework of a molecular crystal model.…”

Section: Introductionmentioning

confidence: 99%

Unified dynamic approach for simulating quantum tunneling and thermionic emission at metal/organic interface

Huang,

Mo,

Yao

2020

Preprint

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Injection from metallic electrodes serves as a main channel of charge generation in organic semiconducting devices and the quantum effect is normally regarded to be essential. We develop a dynamic approach based upon the surface hopping (SH) algorithm and classical device modeling, by which both quantum tunneling and thermionic emission of charge carrier injection at metal/organic interfaces are concurrently investigated. The injected charges from metallic electrode are observed to quickly spread onto the organic molecules following by an accumulation close to the interface induced by the built-in electric field, exhibiting a transition from delocalization to localization.We compare the Ehrenfest dynamics on mean-field level and the SH algorithm by simulating the temperature dependence of charge injection dynamics, and it is found that the former one leads to an improper result that the injection efficiency decreases with increasing temperature at roomtemperature regime while SH results are credible. The relationship between injected charges and the applied bias voltage suggests it is the quantum tunneling that dominates the low-threshold injection characteristics in molecular crystals, which is further supported by the calculation results of small entropy change during the injection processes. An optimum interfacial width for charge injection efficiency at the interface is also quantified and can be utilized to understand the role of interfacial buffer layer in practical devices.

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Ultralow-voltage Auger-electron-stimulated organic light-emitting diodes

Cited by 13 publications

References 57 publications

Higher order effects in organic LEDs with sub-bandgap turn-on

Higher order effects in organic LEDs with sub-bandgap turn-on

All‐Solution‐Processed Pure Formamidinium‐Based Perovskite Light‐Emitting Diodes

Unified dynamic approach for simulating quantum tunneling and thermionic emission at metal/organic interface

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