Magnetic-field effect in organic photoconductive devices studied by time-of-flight

Wang, F.; Rybicki, James; Hutchinson, K. A.; Wohlgenannt, M.

doi:10.1103/physrevb.83.241202

Cited by 9 publications

(4 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Investigations on the magnetic field frequency dependence led to hypothesize that OMAR may be due to a change in minority charge mobility [7,12]. This possibility was further confirmed by time of flight measurements performed on Alq 3 thin films, which showed that carrier mobility can be affected by the magnetic field [13]. Continuous wave (CW) magnetic resonance techniques were also used as alternative methods to investigate spin effects in organic semiconductors [4,5,[14][15][16].…”

Section: Introductionmentioning

confidence: 90%

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Comandè

Ansermet

2013

Synthetic Metals

View full text Add to dashboard Cite

The aim of the present work is to investigate the nature of spin dependent processes in an organic light emitting diode based on a ITO/ α-NPD/Alq3 structure. The electroluminescence time response of the sample is monitored while the OLED is exposed to a high power resonant microwave pulse. Measurements are carried out at room temperature. The time scale of the induced transition is found to be independent of the bias voltage. It is shown, by way of a simulation, that this behavior appears inconsistent with models which attribute a change in the electroluminescence to a variation in charge mobility. Spin dependent processes directly related to a change in the rate of charge recombination play therefore a relevant role in Alq 3 light emitting diodes.

show abstract

Section: Introductionmentioning

confidence: 90%

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Comandè

Ansermet

2013

Synthetic Metals

View full text Add to dashboard Cite

show abstract

“…Various possible mechanisms responsible for the MC and MEL in organic diodes have emerged from these studies. Some models have emphasized the influence of magnetic field on carrier mobility in the device 4,8,14,15 , while other models have emphasized the influence of the magnetic field on the carrier density, brought about by spindependent microscopic processes among polaron-pairs (PP) or triplet excitons (TE) 5,12,16 . A variety of spin-mixing mechanisms have been proposed that include the hyperfine interaction (HFI) between polarons and the skeleton protons in π-conjugated polymers and molecules 3,4,11,12 ; the difference, Δg in the electron and hole g-factors in polymer/fullerene blends [17][18][19] ; a number of mechanisms that involve TE 5,16 ; and the spin-orbit coupling in small molecules that contain heavy atoms 3,20 .…”

Section: Introductionmentioning

confidence: 99%

Magnetic field effect on excited-state spectroscopies ofπ-conjugated polymer films

et al. 2012

View full text Add to dashboard Cite

The magnetic field effect in organic light-emitting diodes, such as magneto-conductance and magneto-electroluminescence has been intensively explored in the last few years. Here we demonstrate magnetic field effect of two excited state spectroscopies in films of a prototype π-conjugated polymer, namely a soluble derivative of poly(phenylene-vinylene) [MEH-PPV]; these are magneto-photoinduced absorption (MPA) and magneto-photoluminescence (MPL). We study these novel magnetic field effects in pristine MEH-PPV films, MEH-PPV films subjected to prolonged illumination, and blend of MEH-PPV with a fullerene derivative. Being spectroscopic in nature, MPA and MPL are determined by the photoexcitation spin density, and thus may unravel the occurrence of a myriad of spin-mixing processes in organic semiconductors that include hyperfine interaction in polaron-pairs, spin-sublevel mixing in triplet excitons, triplet-triplet annihilation, and triplet-singlet collision. The recently observed ultra-small magnetic field effect at B<~0.5 mT in organic diodes is also observed in the MPA response of MEH-PPV films that support polaron photoexcitations, thereby identifying the underlying mechanism as due to spin-mixing of polaron-pairs by the hyperfine interaction.

show abstract

“…Moreover, using electrically detected magnetic resonance (EDMR), it has been shown that dye dopants in Alq 3 organic light-emitting diodes (OLEDs) affect the resonance g factor, suggesting charge trapping followed by recombination as the main mechanism in these devices [12]. On the other hand, a direct effect of magnetic field on mobility has been shown in Alq 3 by using time of flight measurements, as predicted by the bipolaron model [6,13]. Finally, there is also evidence of trap-induced magnetic field effects [14,15].…”

mentioning

confidence: 98%

Time-resolved spin processes inAlq3light-emitting diodes

Comandè

Ansermet

2014

Phys. Rev. B

View full text Add to dashboard Cite

Using pulsed electroluminescence detected magnetic resonance (PELDMR), we study the dynamics of spin processes in Alq 3 based light-emitting diodes. The transitions induced by magnetic resonance are found to be much faster than the space charge reaction time that is measured by looking at the electroluminescence frequency response to an ac bias voltage. This observation excludes a change in the equilibrium space charge distributions as the cause of PELDMR, in favor of a change of the electron-hole recombination rate. At low temperatures the effect of electron spin resonance on the electroluminescence changes sign and lasts longer. The postpulse electroluminescence recovery is well fitted by a biexponential function characterized by two very different time scales, which are consistent with a detailed balance for the singlet and triplet states, in conformity with the electron-hole pair model.

show abstract

Magnetic-field effect in organic photoconductive devices studied by time-of-flight

Cited by 9 publications

References 19 publications

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Pulsed magnetic resonance of Alq3 OLED detected by electroluminescence

Magnetic field effect on excited-state spectroscopies ofπ-conjugated polymer films

Time-resolved spin processes inAlq3light-emitting diodes

Contact Info

Product

Resources

About