Electric field-induced transition from heterojunction to bulk charge recombination in bilayer polymer light-emitting diodes

Morteani, Arne C.; Ho, Peter K. H.; Friend, Richard H.; Silva, Carlos

doi:10.1063/1.1899751

Cited by 37 publications

(40 citation statements)

References 16 publications

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“…Morteani et al have studied polymer:polymer blends and have shown with temperaturedependent measurements that energy transfer from the CT state dominates below 4V, with an endothermic activation energy of 200 meV ± 50 meV. [51][52][53] Since all of the presented EL spectra have been measured at voltages smaller than 4 V, this would suggest that the principal mechanism is energy transfer from the CT state to a component singlet. The activation energy of 200 meV corresponds to about twice the width of the density of states (DOS) of an organic semiconductor, 54 which may suggest that singlet emission is linked to an overlap of CT state emission and singlet absorption.…”

Section: Discussionmentioning

confidence: 99%

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Faist¹,

Kirchartz²,

et al. 2011

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We study the appearance and energy of the charge transfer (CT) state using measurements of Electroluminescence (EL) and Photoluminescence (PL) in blend films of high-performance polymers with fullerene acceptors. EL spectroscopy provides a direct probe of the energy of the interfacial states without the need to rely on the LUMO and HOMO energies as estimated in pristine materials. For each polymer, we use different fullerenes with varying LUMO levels as electron acceptors, in order to vary the energy of the CT state relative to the blend with [6,6]-phenyl C61-butyric acid methyl ester (PCBM). As the energy of the CT state emission approaches the absorption onset of the blend component with the smaller optical bandgap, , we observe a transition in the EL spectrum from CT emission to singlet emission from the component with the smaller bandgap. The appearance of component singlet emission coincides with reduced photocurrent and fill factor. We conclude that the open circuit voltage is limited by the smaller bandgap of the two blend components. From the losses of the studied materials, we derive an empirical limit for the open circuit voltage: 2

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Section: Discussionmentioning

confidence: 99%

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Faist¹,

Kirchartz²,

et al. 2011

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“…Polymeric semiconductors are an exciting class of materials that are now finding commercial applications in light-emitting diodes (LEDs) for electroluminescent displays [1][2][3][4] and show promise in other applications such as in photovoltaic diodes (PVDs). [5][6][7][8][9][10] It is now widely accepted that the primary photoexcitations in phenylene-based π-conjugated polymers are singlet excitons, and that these migrate within the bulk polymer phase by incoherent stepwise hops that are mediated by resonance energy transfer (RET).…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation of Exciton Bimolecular Annihilation Dynamics in Supramolecular Semiconductor Architectures

et al. 2007

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We present a simulation of exciton dynamics in supramolecular assemblies of an oligo-p-phenylenevinylene derivative monofunctionalised with a quadruple hydrogen-bonding group (MOPV). MOPV molecules form helical stacks in dodecane solution through solvophobic and π-π interactions with thermotropic reversibility. We apply a model of incoherent excitation hopping using a Monte Carlo scheme to extract microscopic physical quantities relevant to energy diffusion and bimolecular annihilation processes within isolated nanostructures. We compare the simulation to ultrafast spectroscopic data, namely photoinduced absorption transients at various excitation fluences, their polarization anisotropy, and the dynamic photoluminescence red-shift. We observe that energy diffusion and bimolecular annihilation processes can be described with the same microscopic model based on a Förster-like model that takes into account the spatial extent of the excited state; these two processes are interconnected via the same underlying physics. We extract a high diffusion coefficient (∼0.08 cm 2 s -1 ) over the first few picoseconds following excitation, which plays an important role in dictating the bimolecular annihilation dynamics.

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“…In some nanocomposites, the existence of new recombination mechanisms is suggested by the generation of new PL emission lines, 35 which may be attributed to the formation of interfacial states termed exciplex. 36 Figure 6 depicts the typical afterglow decay curves of the phosphor samples after the powders were activated using a pulsed xenon lamp. The curves show that the BaAl x O y :Eu 2þ ,Dy 3þ phosphor material emits light far longer than the typical microsecond lifetime of Eu 2þ .…”

Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

Luminescent properties of long‐lasting BaAl_xO_y:Eu²⁺,Dy³⁺ nanocomposites

Daniel

Swart

Luyt

et al. 2011

J of Applied Polymer Sci

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BaAl x O y :Eu 2þ ,Dy 3þ blue-green phosphor samples were synthesized by a combustion method at the low temperature of 500 C. Phosphor nanocrystallites with high brightness were obtained without significantly changing the crystalline structure of the host. The crystallite sizes determined from the Scherrer equation ranged between 34 and 41 nm. Different volume fractions of the BaAl x O y :Eu 2þ ,Dy 3þ powder were then introduced in LDPE polymer. The resulting composites were similarly analyzed and also thermally characterized by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). PL results indicate that the LDPE-phosphor interface, which is considered to have an influence on the composite behavior, did not significantly change the spectral positions of the phosphor materials, whose major emission peaks occurred at about 505 nm. The improved afterglow results for the composites may have been caused by morphological changes due to increased surface area and defects. Thermal results indicate that the BaAl x O y :Eu 2þ ,Dy 3þ particles acted as nucleating centers and enhanced the overall crystallinity in the LDPE nanocomposite while preventing lamellar growth, hence reducing the crystallite sizes in LDPE.

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Electric field-induced transition from heterojunction to bulk charge recombination in bilayer polymer light-emitting diodes

Cited by 37 publications

References 16 publications

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Monte Carlo Simulation of Exciton Bimolecular Annihilation Dynamics in Supramolecular Semiconductor Architectures

Luminescent properties of long‐lasting BaAl_xO_y:Eu²⁺,Dy³⁺ nanocomposites

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Electric field-induced transition from heterojunction to bulk charge recombination in bilayer polymer light-emitting diodes

Cited by 37 publications

References 16 publications

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Competition between the Charge Transfer State and the Singlet States of Donor or Acceptor Limiting the Efficiency in Polymer:Fullerene Solar Cells

Monte Carlo Simulation of Exciton Bimolecular Annihilation Dynamics in Supramolecular Semiconductor Architectures

Luminescent properties of long‐lasting BaAlxOy:Eu2+,Dy3+ nanocomposites

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Product

Resources

About

Luminescent properties of long‐lasting BaAl_xO_y:Eu²⁺,Dy³⁺ nanocomposites