Study of magneto-electroluminescence and magneto-conductance in polymer light-emitting electrochemical cells

Ni, Gang; Nguyen, T. D.; Vardeny, Z. Valy

doi:10.1063/1.3605251

Cited by 19 publications

(19 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Large changes in the current and luminescence with magnetic field have been observed in organic semiconducting devices during the last decade [1][2][3][4][5][6][7][8][9][10][11]. Such effects have been investigated in organic light emitting devices (OLEDs) [1][2][3][4], donor acceptor blends [5,6], field effect transistors [7,8], polymer light-emitting electrochemical cells [9,10], and molecular wires [11].…”

Section: Introductionmentioning

confidence: 99%

“…Such effects have been investigated in organic light emitting devices (OLEDs) [1][2][3][4], donor acceptor blends [5,6], field effect transistors [7,8], polymer light-emitting electrochemical cells [9,10], and molecular wires [11]. These magnetic field effects (MFEs) manifest themselves at room temperature and small magnetic fields of only a few millitesla, which has led to the suggestion of cheap plastic sensor applications [12].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Anisotropic magnetoconductance in polymer thin films

et al. 2014

View full text Add to dashboard Cite

The dependence of the magnetic field sensitive current on the orientation of the magnetic field has been investigated in organic semiconductor devices where the active layer consists of the poly(p-phenylene vinylene) derivative "Super Yellow." Previous work on Alq 3 suggested that the anisotropy was caused either by anisotropic spin-spin interactions or by anisotropic hyperfine fields, but no discrimination could be made. In the present work, the anisotropy at the hyperfine field scale is best explained by dipolar coupling between the spin of polarons. In addition, a high field anisotropy is found with an opposite sign, different angle, and voltage dependence. Spin density matrix calculations were performed of polaron pair interactions for the low field effect, and a g-mechanism, triplet-polaron, or triplet-triplet interaction for the high field effect. The simulations confirm that the low field anisotropy can indeed be explained by dipolar coupling. However, the proposed models can not entirely account for the high field anisotropy. These results show that, although contemporary models can account for (anisotropic) magnetic field effects in organic semiconductors at low field scales, more experimental and theoretical research of high field effects is highly desirable.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anisotropic magnetoconductance in polymer thin films

et al. 2014

View full text Add to dashboard Cite

show abstract

“…OMAR in LECs biased above the semiconductor band gap has been reported by Vardeny et al 14 They observed a positive magnetoconductance (MC) of ∼0.4% and magnetoelectroluminescence (MEL) of ∼5%. The results were explained by the polaron pair model.…”

Section: Introductionmentioning

confidence: 94%

Large magnetic field effects in electrochemically doped organic light-emitting diodes

et al. 2013

View full text Add to dashboard Cite

Large negative magnetoconductance (MC) of ∼12% is observed in electrochemically doped polymer light-emitting diodes at sub-band-gap bias voltages (V bias ). Simultaneously, a positive magnetoefficiency (Mη) of 9% is observed at V bias = 2 V. At higher bias voltages, both the MC and Mη diminish while a negative magnetoelectroluminescence (MEL) appears. The negative MEL effect is rationalized by triplet-triplet annihilation that leads to delayed fluorescence, whereas the positive Mη effect is related to competition between spin mixing and exciton formation leading to an enhanced singlet:triplet ratio at nonzero magnetic field. The resultant reduction in triplet exciton density is argued to reduce detrapping of polarons in the recombination zone at low-bias voltages, explaining the observed negative MC. Regarding organic magnetoresistance, this study provides experimental data to verify existing models describing magnetic field effects in organic semiconductors, which contribute to better understanding hereof. Furthermore, we present indications of strong magnetic field effects related to interactions between trapped carriers and excitons, which specifically can be studied in electrochemically doped organic light-emitting diodes (OLEDs). Regarding light-emitting electrochemical cells (LECs), this work shows that delayed fluorescence from triplet-triplet annihilation substantially contributes to the electroluminescence and the device efficiency.

show abstract

“…The positive MEL component at small applied field might be caused by the ISC between singlet and triplet e-h pairs that has been previously explained for MEL in OLEDs. 2,5,12,23,24 The negative component seen at the large field is almost twice as large as MC, which might be a result of the change in current density. This can be explained by the magnetic field acting on one type of carriers where the bipolaron and p-dimer concepts are used.…”

mentioning

confidence: 94%

“…Furthermore, it can influence the spin mixing between the triplet excitons and charges; it therefore changes mobility of the device. Recently, there has been interest in studying OMAR in polymer light-emitting electrochemical cells (PLECs) 23,24 in a vertical device configuration. Both negative and positive MCs were observed and were dependent on the use of electrolytes, while positive MEL was always observed.…”

mentioning

confidence: 99%

Tunable magneto-conductance and magneto-electroluminescence in polymer light-emitting electrochemical planar devices

Geng

Mayhew

Nguyen

2013

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

We report studies of magneto-conductance (MC) and magneto-electroluminescence (MEL) in polymer light-emitting electrochemical planar devices using “super-yellow” poly-(phenylene vinylene). We observed consistent negative MC while MEL becomes positive when electroluminescence quantum efficiency (ELQE) increases. At an optimal ELQE, the MC has a much narrower width than the MEL, indicating that the MC and MEL do not share a common origin. However, MC reverses and has the same width as MEL when exposed to a threshold laser power. We show that the e-h pair model can explain the positive MEL and MC while the negative MC can be explained by the bipolaron model.

show abstract

Study of magneto-electroluminescence and magneto-conductance in polymer light-emitting electrochemical cells

Cited by 19 publications

References 19 publications

Anisotropic magnetoconductance in polymer thin films

Anisotropic magnetoconductance in polymer thin films

Large magnetic field effects in electrochemically doped organic light-emitting diodes

Tunable magneto-conductance and magneto-electroluminescence in polymer light-emitting electrochemical planar devices

Contact Info

Product

Resources

About