Energy disorder and energy level alignment between host and dopant in organic semiconductors

Li, Peicheng; Ingram, Grayson L.; Lee, Jaejin; Zhao, Yongbiao; Lu, Zheng‐Hong

doi:10.1038/s42005-018-0101-9

Cited by 22 publications

(22 citation statements)

References 22 publications

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“…[ 57 ] However, the incorporation of TTM‐3NCz into the CBP film is expected to raise the dielectric constant. We note that earlier theoretical investigations have used a value ε = 3.5 to describe the energy level alignment between CBP and guest emitters; [ 58 ] switching to ε = 3.5 in our calculations decreases the D 1 state energies by about 0.1 eV.…”

Section: Resultsmentioning

confidence: 76%

Radiative and Nonradiative Recombinations in Organic Radical Emitters: The Effect of Guest–Host Interactions

Abroshan

Coropceanu

Brédas

2020

Adv Funct Materials

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Radical‐carrying organic molecules have received significant attention to bypass the issue related to harvesting triplet excitons in current light‐emitting materials. While the computational efforts conducted so far have treated these radical emitters as isolated entities, in actual devices, they are embedded in a host matrix and subject to emitter–host interactions. Here, by combining molecular dynamics simulations and density functional theory calculations, the impact of the host matrix on the optoelectronic performance of radical emitters is evaluated, taking as a representative example the (4‐ncarbazolyl‐2,6‐dichlorophenyl)bis(2,4,6‐trichlorophenyl)‐methyl (TTM‐3NCz) radical emitter dispersed in a 4,4‐bis(carbazol‐9‐yl)biphenyl (CBP) host. A morphological analysis shows that steric effects around the radical centers, carried by the TTM electron‐poor moieties of the emitters, disfavor π–π interactions with the host molecules, which leads to random intermolecular orientations around the TTM moieties. The 3NCz electron‐rich moieties of the emitters, however, have much lesser spatial hindrance for intermolecular π–π stacking, which modulates the structural and electronic properties of the emitters in the host matrix. The influence of dynamic and static disorders on the radiative and nonradiative recombination processes is also investigated and it is found that the rates of nonradiative recombination are small, which opens the way to 100% internal quantum efficiency for the doublet‐based emission process.

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Section: Resultsmentioning

confidence: 76%

Radiative and Nonradiative Recombinations in Organic Radical Emitters: The Effect of Guest–Host Interactions

Abroshan

Coropceanu

Brédas

2020

Adv Funct Materials

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“…4b, d). As noted in recent studies, this highlights the importance of considering not just the energetic offset between host and dopant, but also the energetic disorder of the system as this can severely impact the doping efficiency 8,9,34 .…”

Section: Resultsmentioning

confidence: 77%

Controlling energy levels and Fermi level en route to fully tailored energetics in organic semiconductors

et al. 2019

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Simultaneous control over both the energy levels and Fermi level, a key breakthrough for inorganic electronics, has yet to be shown for organic semiconductors. Here, energy level tuning and molecular doping are combined to demonstrate controlled shifts in ionisation potential and Fermi level of an organic thin film. This is achieved by p-doping a blend of two host molecules, zinc phthalocyanine and its eight-times fluorinated derivative, with tunable energy levels based on mixing ratio. The doping efficiency is found to depend on host mixing ratio, which is explained using a statistical model that includes both shifts of the host’s ionisation potentials and, importantly, the electron affinity of the dopant. Therefore, the energy level tuning effect has a crucial impact on the molecular doping process. The practice of comparing host and dopant energy levels must consider the long-range electrostatic shifts to consistently explain the doping mechanism in organic semiconductors.

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“…When in contact with another material, asymmetrical interaction at the interface can cause molecule rearrangement and charge transfer, leading to additional energy disorder for organic molecules at interfaces. [ 54–56 ] We have previously observed an increase in energy disorder of organic semiconductors at electrode–organic interfaces. [ 56 ] As shown in Figure 2b, the HOMO of copper (II) phthalocyanine (CuPc) is broadened at the interface and its full width at half maximum (FWHM) increases with decreasing film thickness.…”

Section: Energy Disorders In Thin‐film Organic Semiconductorsmentioning

confidence: 99%

Interface Engineering in Organic Electronics: Energy‐Level Alignment and Charge Transport

2020

Small Science

Self Cite

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Organic light‐emitting diodes (OLEDs) and organic solar cells are new members of trillion‐dollar semiconductor industry. The structure of these devices generally consists of a stack of several organic layers sandwiched between two electrodes. The electronic processes such as the energy‐level alignment at and charge transport across these interfaces play a key role to the overall performance of the organic devices. Thus, interface physics is important for design and engineering of organic devices. Herein, recent progress in energy‐level alignment at and charge transport across organic interfaces is reviewed. In addition, basic material physics of organic semiconductors such as energy levels, energy disorder, and molecular orientation is introduced. Recent progress in theories and experiments on energy‐level alignment at and charge transport across molecular heterojunctions is then discussed. Case studies of applying interface physics for guiding fabrication of ideal devices are also provided.

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Energy disorder and energy level alignment between host and dopant in organic semiconductors

Cited by 22 publications

References 22 publications

Radiative and Nonradiative Recombinations in Organic Radical Emitters: The Effect of Guest–Host Interactions

Radiative and Nonradiative Recombinations in Organic Radical Emitters: The Effect of Guest–Host Interactions

Controlling energy levels and Fermi level en route to fully tailored energetics in organic semiconductors

Interface Engineering in Organic Electronics: Energy‐Level Alignment and Charge Transport

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