Effect of Charge Localization on the Effective Hyperfine Interaction in Organic Semiconducting Polymers

Geng, Rugang; Subedi, Ram Chandra; Luong, Hoang Mai; Pham, Minh Thien; Huang, Wen Chen; Li, Xiaoguang; Hong, Kunlun; Shao, M.; Xiao, Kai; Hornak, L.A.; Nguyen, Tho Duc

doi:10.1103/physrevlett.120.086602

Cited by 34 publications

(32 citation statements)

References 49 publications

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“…Moreover, the feature of the smaller width in the hole carrier corresponds well with the recent reports that the MC curve of the hole-only device in polymer OLEDs is narrowed than that of the electron-only device. 33 We thus conclude that the smaller width component of the EDMR and ELDMR spectra in the OLED is given by the hole carrier. This is consistent with the conclusion of the recent report drawn from a comparison of the measured and simulated EDMR spectra in the high-magnetic field EDMR for the OLED of 2-methoxy, 5-(2 0 -ethyl-hexyloxy)-(MEH-) PPV.…”

Section: Journal Of Applied Physicsmentioning

confidence: 59%

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: Journal Of Applied Physicsmentioning

confidence: 59%

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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“…According to the literature, the electron and hole reside primarily in ligand 2 and ligand 1 of an Alq 3 molecule respectively, as www.nature.com/scientificreports/ shown in Fig. 4a,b [46][47][48][49][50][51] , and the intensity for the local hyperfine interaction is inverse proportional to the size of the localization of the polaron 44 . From Fig.…”

Section: Model Fitting and Analysismentioning

confidence: 99%

Fitting the magnetoresponses of the OLED using polaron pair model to obtain spin-pair dynamics and local hyperfine fields

Weng

Gillin

Kreouzis

2020

Sci Rep

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Organic light-emitting diode (OLED) displays a sign reversal magnetic field effect (MFE) when the applied magnetic field range is reduced to the sub-milliTesla range and the Polaron Pair Model has been successful in explaining the ultra-small MFE. Here, we obtained high resolution (~ 1 µT) magnetoconductance (MC) and magnetoelectroluminescence (MEL) of a tris-(8-hydroxyquinoline)aluminium-based (Alq3) OLED within the magnetic field range of ± 500 µT with the earth magnetic field components cancelled. A clear “W” shaped MC with a dip position of ± 250 µT and a monotonic MEL were observed. We demonstrate a fitting technique using the polaron pair model to the experimentally obtained MC and MEL. The fitting process extracts physically significant parameters within a working OLED: the local hyperfine fields for electron and hole in Alq3: Bhf1 = (0.63 ± 0.01) mT (electron), Bhf2 = (0.24 ± 0.01) mT (hole); the separation rates for singlet and triplet polaron pairs: kS,s = (44.59 ± 0.01) MHz, kT,s = (43.97 ± 0.01) MHz, and the recombination rate for singlet polaron pair kS,r = (88 ± 6) MHz. The yielded parameters are highly reproducible across different OLEDs and are in broad agreement with density functional theory (DFT) calculations and reported experimental observations. This demonstrates the feasibility of this fitting technique to approach any working OLED for obtaining significant microscopic parameters.

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“…This is the principle for spin mixing mechanisms in the loosely bound electron-hole pair model, and the bipolaron model (spin mixing between two polarons of the same kind) for MFE. [13][14][15][16][17] For estimating the average strength of the induced magnetic field of MNPs in their proximity, we performed a micromagnetic simulation of the induced magnetic field using an open source calculation code, OOMMF (The Object Oriented MicroMagnetic Framework). For simplicity, we assume that MNPs with parallel magnetization are dispersed uniformly in the MeH-PPV host.…”

Section: Figure 2amentioning

confidence: 99%

“…22,[31][32][33][34] modified the HFI strengths of hydrogenated OSECs. [13][14]36 Although this method uniformly manipulates the HFI strength at specified locations in the molecule, it does not offer dynamical control of the interaction. On the other hand, the ENDOR spectroscopy is primarily directed to study the magnetic interactions of the unpaired electron spin with the spins of magnetic nuclei (or HFI) by employing the combined electron paramagnetic resonance (EPR) and the nuclear magnetic resonance (NMR) techniques.…”

Section: Introductionmentioning

confidence: 99%

Magnetically tunable organic semiconductors with superparamagnetic nanoparticles

et al. 2019

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maximum 250 words) Magnetic nanoparticles (MNPs) exhibiting superparamagnetic properties might generate large magnetic dipole-dipole interaction with electron spins in organic semiconductors (OSECs). This concept could be considered analogous to the effect of hyperfine interaction (HFI). In order to investigate this model, Fe3O4 MNPs are used as a dopant for generating random hyperfine-like magnetic fields in a HFI-dominant π-conjugated polymer host, poly(2-methoxy-5-(2ethylhexyloxy)-1,4-phenylenevinylene) (MeH-PPV). The magnetoconductance (MC) response in organic light emitting diodes made by MeH-PPV/MNP blends is used to estimate the effective hyperfine field in the blends. Firstly, we find that the shape of the MC response essentially remains the same regardless of the MNP concentration, which is attributed to the similar functionality between the nuclear spins and magnetic moments of the MNPs. Secondly, the width of the MC response increases with increasing MNP concentration. Magneto-optical Kerr effect (MOKE) experiments and micromagnetic simulation indicate that the additional increase of the MC width is associated with the magnetization of the blend. Finally, the MC broadening has the same temperature dependent trend as the magnetization of the MNPs where the unique effect of the MNPs in their superparamagnetic and ferromagnetic regimes on the MC response is observed. Magneto-photoinduced absorption (MPA) spectroscopy confirms that the MC broadening is not due to defects introduced by the MNPs but a result of their unique superparamagnetic behavior. Our study yields a new pathway for tuning OSECs' magnetic functionality, which is essential for organic optoelectronic devices and magnetic sensor applications.Keywords: organic semiconductor, magnetic nanoparticle, magnetic field effect, hyperfine interaction, coherent spin mixing rate.Recently, there has been interest in coherent spin manipulation via controlling of the HFI by several state-of-the-art methods, including isotope exchange with different nuclear spins and pulsed electron-nuclear double resonance (ENDOR) spectroscopy. 13-15, 30, 35-38 The former method chemically replaces particular atoms in the molecule by atoms with different nuclear spins. [13][14][35][36][37] In conventional conducting polymers, the presence of new isotopes, e.g. 2 H and 13 C, significantly

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Effect of Charge Localization on the Effective Hyperfine Interaction in Organic Semiconducting Polymers

Cited by 34 publications

References 49 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

Fitting the magnetoresponses of the OLED using polaron pair model to obtain spin-pair dynamics and local hyperfine fields

Magnetically tunable organic semiconductors with superparamagnetic nanoparticles

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