Electric field-induced photoluminescence quenching in thin-film light-emitting diodes based on poly(phenyl-p-phenylene vinylene)

Deussen, M.; Scheidler, M.; Bäßler, H.

doi:10.1016/0379-6779(95)03307-6

Cited by 156 publications

(141 citation statements)

References 27 publications

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“…This can be seen in Figure 2, where the individual optically and electrically excited signals perfectly add up to the simultaneously excited one, that is, the optically excited fluorescence contribution in the presence of the electrical excitation is unchanged. This also shows that for singlet excitons, quenching by the electric field [99] or by polarons [100] is negligible under the conditions used in our experiments. For the triplet signal, either triplet transient absorption [90,101] or phosphorescence [85] could be used.…”

Section: Experimental Observationsmentioning

confidence: 52%

Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

Monkman

2013

ISRN Materials Science

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A potential major drawback with organic light-emitting devices, (OLEDs) is the limit of 25% singlet exciton production through spin-dependent charge recombination. Recent device results, however, show that this limit does not hold and far higher efficiencies can be achieved in purely fluorescent-based systems (Wohlgenannt et al. (2012)). Here, the various routes by which triplet excitons can generate singlet states are discussed and their relative contributions to the overall electroluminescence yield are given. The materials requirements to obtain maximum singlet production from triplet states are discussed. These triplet contributions can give very high device yields for fluorescent emitters, which in the case of blue devices can be highly advantageous. Further, new devices architectures open up which are simple and have intrinsically low turn on voltages, ideal for large-area OLED lighting applications.

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Section: Experimental Observationsmentioning

confidence: 52%

Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

Monkman

2013

ISRN Materials Science

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“…It is also notable that the triplet exciton density is not significantly quenched by the application of a 10V reverse bias pulse because the triplets are considerably more stable than singlets to the electric field due to their inherently greater exciton binding energy. 27,28 Equation (2) shows the kinetic scheme for the decay of the triplet population,…”

Section: Resultsmentioning

confidence: 99%

The contribution of triplet–triplet annihilation to the lifetime and efficiency of fluorescent polymer organic light emitting diodes

King¹,

Cass²,

Pintani³

et al. 2011

Journal of Applied Physics

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We demonstrate that the fast initial decay of a prototypical fluorescent polymer based organic light emitting diode device is related to the contribution that triplet–triplet annihilation makes to the device efficiency. We show that, during typical operating conditions, approximately 20% of the device efficiency originates from the production of singlet excitons by triplet–triplet annihilation. During prolonged device operation, the triplet excitons are quenched much more easily than the emissive singlets; thus, the contribution to the efficiency from triplet–triplet annihilation is lost during the early stages of the device lifetest. The fast initial decay of the device luminance can be removed by incorporating a triplet quenching additive into the active layer to remove any effect of triplet–triplet annihilation; this yields an increase in the device lifetime of greater than 3× and an even more significant improvement in the initial luminance decay.

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“…[10] One of the most convincing quantitative assessments of the exciton binding energy magnitude is provided by studying the photoluminescence quenching resulting from an electric field. [42,43] The dissociation of an excited singlet state of a conjugated polymer requires field-assisted transfer of the constituent charges to a neighboring chain or chain segment. In a first order approximation, this would occur if the gain in electrostatic energy, eEDz, where e is the electric charge, E the internal electric field, and Dz the distance between the charges, compensates for the energy expense for the charge transfer in zero field.…”

Section: Creation Of Excitonsmentioning

confidence: 99%

Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells

et al. 2007

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Plastic solar cells bear the potential for large‐scale power generation based on materials that provide the possibility of flexible, lightweight, inexpensive, efficient solar cells. Since the discovery of the photoinduced electron transfer from a conjugated polymer to fullerene molecules, followed by the introduction of the bulk heterojunction (BHJ) concept, this material combination has been extensively studied in organic solar cells, leading to several breakthroughs in efficiency, with a power conversion efficiency approaching 5 %. This article reviews the processes and limitations that govern device operation of polymer:fullerene BHJ solar cells, with respect to the charge‐carrier transport and photogeneration mechanism. The transport of electrons/holes in the blend is a crucial parameter and must be controlled (e.g., by controlling the nanoscale morphology) and enhanced in order to allow fabrication of thicker films to maximize the absorption, without significant recombination losses. Concomitantly, a balanced transport of electrons and holes in the blend is needed to suppress the build‐up of the space–charge that will significantly reduce the power conversion efficiency. Dissociation of electron–hole pairs at the donor/acceptor interface is an important process that limits the charge generation efficiency under normal operation condition. Based on these findings, there is a compromise between charge generation (light absorption) and open‐circuit voltage (VOC) when attempting to reduce the bandgap of the polymer (or fullerene). Therefore, an increase in VOC of polymer:fullerene cells, for example by raising the lowest unoccupied molecular orbital level of the fullerene, will benefit cell performance as both fill factor and short‐circuit current increase simultaneously.

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Electric field-induced photoluminescence quenching in thin-film light-emitting diodes based on poly(phenyl-p-phenylene vinylene)

Cited by 156 publications

References 27 publications

Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

The contribution of triplet–triplet annihilation to the lifetime and efficiency of fluorescent polymer organic light emitting diodes

Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells

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