Origin of the positive spin-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mfrac><mml:mn>1</mml:mn><mml:mn>2</mml:mn></mml:mfrac></mml:math>photoluminescence-detected magnetic resonance in π-conjugated materials and devices

Chen, Ying; Cai, Min; Hellerich, Emily; Shinar, Ruth; Shinar, J.

doi:10.1103/physrevb.92.115203

Cited by 8 publications

(13 citation statements)

References 23 publications

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“…In fact, the EDMR and ELDMR signals of OLEDs were previously explained by being due to the trions. 25,26 Contributions from the former trions can be examined from EDMR or ELDMR responses at the half…”

Section: A Esr Characteristicsmentioning

confidence: 99%

Correlation between bias-dependent ESR signals and magnetic field effects in organic light emitting diodes

Kanemoto

Hatanaka

Suzuki

2019

Journal of Applied Physics

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The bias dependent behaviors in magnetic field effects (MFEs) of the current and the electroluminescence (EL) intensity in organic light emitting diodes (OLEDs) have been investigated from electrically-detected and EL-detected magnetic resonance (EDMR and ELDMR) techniques. An EDMR signal was not detected from the electron-only device, and the hole-only device gave only a much smaller EDMR signal than the OLED device. Both the EDMR and ELDMR signals observed from the OLED are concluded to primarily arise from the spin-dependent reaction of electron-hole (e-h) pairs. Both the normalized EDMR and ELDMR signal intensities decrease by increasing the operation bias of OLED, because the increased bias enhances the dissociation and recombination of e-h pairs beyond the increase in the pair-density by the bias. The bias-dependence curves of magneto-conductances and magneto-EL intensities are demonstrated to be very similar to those of the normalized EDMR and ELDMR, respectively. This similarity gives direct evidence that e-h pairs determine the MFEs of the present OLEDs at room temperature and that the MFEs are reduced by bias-dependent dissociation and recombination of e-h pairs. The bias-dependent EDMR and ELDMR experiments are thus effective as probing methods to examine the magnetic field properties via e-h pairs of OLEDs.

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Section: A Esr Characteristicsmentioning

confidence: 99%

Correlation between bias-dependent ESR signals and magnetic field effects in organic light emitting diodes

Kanemoto

Hatanaka

Suzuki

2019

Journal of Applied Physics

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“…In this case, device current changes will, of course, also induce recombination rate changes. An example of a spin-dependent transport mechanism which has previously been resolved directly in MEH-PPV devices is the quenching interaction between triplet excitons and charge carriers, the socalled triplet exciton-polaron mechanism [14,[43][44][45][46][47][48][49]. This process depends on triplet density and triplet lifetime, and therefore on temperature and exhibits clear signatures of s=1 triplet species in the half-field magnetic resonance.…”

Section: Introductionmentioning

confidence: 99%

Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

et al. 2016

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Spin-dependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure single-carrier spin-dependent transport processes which control the current and therefore the electroluminescence, and spin-dependent electron-hole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in two derivatives of the conjugated polymer poly(phenylene-vinylene) using simultaneously measured pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic resonance spectroscopy. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions. This observation is inconsistent with the hypothesis that these signals are caused by spin-dependent charge carrier transport. These results therefore provide no evidence that supports earlier claims that spindependent transport plays a role for room temperature magnetoresistance effects. At low temperatures, however, the correlation between pEDMR and pODMR is weakened, demonstrating that more than one spin-dependent process influences the optoelectronic materials properties. This conclusion is consistent with prior studies of half-field resonances that were attributed to spin-dependent triplet exciton recombination which becomes significant at low temperatures when the triplet lifetime increases. PACS

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“…The mechanism of PLDMR and PCDMR signals in polymer diodes has been discussed in several references [16,17,20,21]. Shinar and co-workers regarded spin-dependent reactions between TEs and polarons as relevant to the PLDMR mechanism [17,22]. However, the intersystem crossing from SE to TE in MEH-PPV was predicted to be inefficient [23,24].…”

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confidence: 99%

Field-induced dissociation of electron-hole pairs in organic light emitting diodes monitored directly from bias-dependent magnetic resonance techniques

Kanemoto

Hatanaka

Kimura

et al. 2017

Phys. Rev. Materials

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Origin of the positive spin-12photoluminescence-detected magnetic resonance in π-conjugated materials and devices

Cited by 8 publications

References 23 publications

Correlation between bias-dependent ESR signals and magnetic field effects in organic light emitting diodes

Correlation between bias-dependent ESR signals and magnetic field effects in organic light emitting diodes

Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

Field-induced dissociation of electron-hole pairs in organic light emitting diodes monitored directly from bias-dependent magnetic resonance techniques

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