Direct Measurement of the Triplet Exciton Diffusion Length in Organic Semiconductors

Mikhnenko, Oleksandr V.; Ruiter, Roald; Blom, Paul W. M.; Loi, Maria Antonietta

doi:10.1103/physrevlett.108.137401

Cited by 48 publications

(37 citation statements)

References 34 publications

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“…A similar trend is observed by Gonzales et al for doped P3HT:PCBM solar cells [24]. The results for exciton diffusion lengths and lifetime conform with the experimental values within ideal material setups, documented in [63,64,86,99]. Similar to the trend observed in [24,26], the lifetime of excitons decreases with dopant concentration.…”

Section: Impact Of Dopant Volume Concentration On Exciton Dynamicssupporting

confidence: 76%

Generalized Kinetic Monte Carlo Framework for Organic Electronics

et al. 2018

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Abstract:In this paper, we present our generalized kinetic Monte Carlo (kMC) framework for the simulation of organic semiconductors and electronic devices such as solar cells (OSCs) and light-emitting diodes (OLEDs). Our model generalizes the geometrical representation of the multifaceted properties of the organic material by the use of a non-cubic, generalized Voronoi tessellation and a model that connects sites to polymer chains. Herewith, we obtain a realistic model for both amorphous and crystalline domains of small molecules and polymers. Furthermore, we generalize the excitonic processes and include triplet exciton dynamics, which allows an enhanced investigation of OSCs and OLEDs. We outline the developed methods of our generalized kMC framework and give two exemplary studies of electrical and optical properties inside an organic semiconductor.

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Section: Impact Of Dopant Volume Concentration On Exciton Dynamicssupporting

confidence: 76%

Generalized Kinetic Monte Carlo Framework for Organic Electronics

et al. 2018

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“…A simple resonator effect caused by the upper crystal can be immediately excluded, because the enhancement was observed without any excitation of the upper cavity crystal. Moreover, exciton transfer from the bottom to the top crystal can also be completely ruled out based on the result of position-dependence excitation, because the exciton diffusion length of organic materials is much less than 100 μm3839. Therefore, the strong improvement in the threshold energy can only be explained by optical coupling between the bottom crystal and the optical resonator (the upper crystal).…”

Section: Discussionmentioning

confidence: 99%

Organic Single-Crystal Light-Emitting Transistor Coupling with Optical Feedback Resonators

Bisri

Sawabe

Imakawa

et al. 2012

Sci Rep

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Organic light-emitting transistors (OLETs) are of great research interest because they combine the advantage of the active channel of a transistor that can control the luminescence of an in-situ light-emitting diode in the same device. Here we report a novel single-crystal OLET (SCLET) that is coupled with single crystal optical feedback resonators. The combination of single-crystal waveguides with native Fabry-Perot cavities, formed by parallel crystal edges, drastically lowers the threshold energy for spectral narrowing and non-linear intensity enhancement. We apply this structure to SCLETs and demonstrate the first fabrication of a SCLET with the optical feedback resonators.

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“…Also, no PQIr emission was observed at any current density for devices with the sensing layer placed at the neat 4,40-bis(3-methylcarbazol-9-yl)-2,20-biphenyl (mCBP)/ tris(8-hydroxyquinolinato)aluminum (Alq 3 ) interface, indicating that the blocking effi ciency of the hole and exciton blocking layer (HBL) is unity. Finally, no emission was observed for sensing layers inserted immediately adjacent to the hexaazatriphenylene hexacarbonitrile (HATCN) layer despite the NPD triplet exciton diffusion length of L D 87nm [ 21 ] which implies excitons in the HTL can diffuse across the 20 nm layer thickness to this interface. HATCN has been shown to effi ciently dissociate excitons in organic photovoltaics due to its deep energy levels.…”

Section: Communicationmentioning

confidence: 94%

Charge Balance and Exciton Confinement in Phosphorescent Organic Light Emitting Diodes

Coburn

Lee

Forrest

2016

Advanced Optical Materials

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local density of excitons, into both the PHOLED charge transport layers and the EML. This is, to our knowledge, the fi rst time that sensing layers have been used to measure charge and exciton leakage into transport layers, and to directly determine the dependence of charge balance and the extent of the exciton formation zone on current. Our results suggest a modifi ed structure with improved blocking characteristics leading to higher effi ciency and potentially longer device lifetime.An understanding of charge transport and the exciton density distribution is necessary to determine the effi cacy of a particular choice of blocking layer material. Charges injected at the electrodes are transported into the EML where they eventually recombine to form excitons, or are transported into an adjacent layer and lost to nonradiative recombination or are collected at the electrodes. Driftdiffusion with thermionic emission over energy barriers between layers can describe the charge balance and carrier distribution in the PHOLED [ 5,8,9 ] yielding the following expressionswith the boundary conditions ofand ( ) 0 a b i . Here, x = 0 corresponds to the position at the anode side of the EML, and x = L at the cathode. Also, E(x,t) is the electric fi eld at x and time t , q is the charge, k is Boltzmann's constant, T is the temperature, and ε is the dielectric constant of the material. Also, J x t n ( , ) is the electron current density, x t n ( , ) μ is its mobility, n x t ( , ) is the electron density, p x t ( , ) is the hole density, Va is the applied voltage, Vbi is the built-in voltage, E 0 is a reference electric fi eld, φ is the frontier orbital energy difference across an interface, and t E t d ( ) ( ) φ Δ = is the potential difference across the interface of width d . The hole current density, J x t p ( , ), is found using an expression analogous to Equation ( 1) . The Einstein relation is used to relate mobility to the diffusion constant, and thermionic emission over barriers has a Poole-Frenkel type fi eld dependence common to organics. [ 10 ] The solution to these equations determine the charge balance, given by Charge Balance and Exciton Confi nement in Phosphorescent Organic Light Emitting DiodesCaleb Coburn , Jaesang Lee , and Stephen R. Forrest* DOI: 10.1002/adom.201600067We study the charge balance and exciton confi nement in blue phosphorescent organic light emitting devices (PHOLEDs) by strategically placing ultrathin, red phosphorescent layers whose emission intensity is proportional to the local density of excitons at several locations within the device. Based on measured exciton distributions, we derive a model for understanding those materials properties that determine charge and exciton transport and confi nement, as well as for interpreting the experimental exciton profi les. We fi nd that triplet exciton leakage results from the very large energy gaps characteristic of blue phosphors, and demonstrate increased lifetime and efficiency in devices with improved exciton confi nement within the diode emission...

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Direct Measurement of the Triplet Exciton Diffusion Length in Organic Semiconductors

Cited by 48 publications

References 34 publications

Generalized Kinetic Monte Carlo Framework for Organic Electronics

Generalized Kinetic Monte Carlo Framework for Organic Electronics

Organic Single-Crystal Light-Emitting Transistor Coupling with Optical Feedback Resonators

Charge Balance and Exciton Confinement in Phosphorescent Organic Light Emitting Diodes

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