Electron mobility in tris(8-hydroxyquinoline)aluminum (Alq3) films by transient electroluminescence from single layer organic light emitting diodes

Park, Hoon; Shin, Dong Yeok; Yu, H.-L.; Chae, Hee-Baik

doi:10.1063/1.2734386

Cited by 53 publications

(36 citation statements)

References 21 publications

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“…(6) to the observed behavior yields the SE decay time τ SE = 8.7 ns, which is consistent with the C6 radiative lifetime τ rad < 10 ns. 34 The inset of Fig. 6 shows the dependence of and τ ccp on the bias.…”

Section: Model Analysismentioning

confidence: 99%

Transient electroluminescence spikes in small molecular organic light-emitting diodes

Gan

Shinar

et al. 2011

Phys. Rev. B

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A comprehensive study of transient ns electroluminescence (EL) spikes that exceed the dc level and μs-long EL tails following a bias pulse in guest-host small molecular organic light-emitting diodes (SMOLEDs), including relatively efficient devices, which elucidates carrier and exciton dynamics in such devices, is presented. The transient EL is strongly dependent, among other parameters, on device materials and structure. At low temperatures, all measured devices, with the exception of Pt octaethylporphyrin (PtOEP)-doped tris(8-hydroxyquinoline) Al (Alq 3 ) SMOLEDs, exhibit the spikes at ~70-300 ns. At room temperature (RT), however, only those with a hole injection barrier, carrier-trapping guest-host emitting layer, and no strong electron-transporting and hole-blocking layer (such as 4,7-diphenyl-1,10-phenanthroline (BPhen)) exhibit strong spikes. These narrow and appear earlier under post-pulse reverse bias. To further elucidate the origin of the spikes, we monitored their dependence on the pulsed bias width and voltage, the doped layer thickness, and its location within the OLED structure. The characteristics of the μs-long tails were also

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Section: Model Analysismentioning

confidence: 99%

Transient electroluminescence spikes in small molecular organic light-emitting diodes

Gan

Shinar

et al. 2011

Phys. Rev. B

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“…4, it is interpreted that γ decreases with increasing voltages. If γ obeys the Langevin formalism (γ = e(µ e +µ h )/ε 0 ε∼eµ e /ε 0 ε, where µ e,h are mobility of electron and hole, respectively, and µ e >>µ h ), its result will be clearly incorrect from the voltage-dependence of electron mobility in Alq 3 [6]. Kalinowski model cannot explain the voltage-dependence of the slope.…”

Section: Resultsmentioning

confidence: 89%

“…Over the past a decade, many researchers have reported the determination of carrier mobility using transient electroluminescence (EL) [1][2][3][4][5][6]. They have observed the delay time, which is the time lag between the pulse application time and the onset of EL and determined the carrier mobility of several organic materials using theoretical equations [4].…”

Section: Introductionmentioning

confidence: 99%

Studies on dynamics of charge carrier in organic electroluminescent devices

Takada

Kamata

2008

Phys. Status Solidi (c)

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Under high current density, lots of organic electroluminescent devices (OELDs) exhibit a substantial decrease in an external quantum coefficient (ηext). Understanding the operating principles of the device is necessary to control the ηext roll off and achieve good performance of OELDs. In this study, we mainly discuss the possible dynamics of charge carrier in our device according to the transient behaviors of electroluminescence (EL) and current after voltage pulse was turn off. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…For Alq 3 , the measured value of mobility was 1 Â 10 À6 cm 2 /Vs at a field 10 6 V/cm, which is very much closer to the value observed in many reports. 43,44 The measured mobility increases with the increase in doping concentration. For the field 10 6 V/cm, the electron mobility for 15 wt.…”

Section: Resultsmentioning

confidence: 99%

Effect of doping of 8-hydroxyquinolinatolithium on electron transport in tris(8-hydroxyquinolinato)aluminum

Kumar

Srivastava

Tyagi

et al. 2011

Journal of Applied Physics

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Effect of doping of 8-hydroxyquinolinatolithium (Liq) on the electron transport properties of tris(8-hydroxyquinolinato)aluminum (Alq 3 ) has been investigated as a function of temperature and doping concentration by fabricating electron only devices. It has been observed that current density in the devices increases with the doping of Liq up to a doping concentration of 33 wt. % and then decreases. Current density-voltage (J-V) characteristics of 0, 15, and 33 wt. % Liq doped Alq 3 devices were found to be bulk limited and analyzed on the basis of trap charge limited conduction model. The J-V characteristics of 50 and 100 wt. % Liq doped Alq 3 devices were found to be injection limited and were analyzed using the Fowler-Nordheim model. The increase in current density with doping up to 33 wt. % was found to be due to an increase in electron mobility upon doping, whereas the decrease in current density above 33 wt. % was due to the switching of transport mechanism from bulk limited to injection limited type due to an increase in barrier height. Electron mobility and variance of energy distribution have been measured by using transient electroluminescence technique to support our analysis. Electron mobility for pure Alq 3 was found to be 1 Â 10 À6 cm 2 /V s, which increased to 3 Â 10 À5 cm 2 /V s upon doping with 33 wt. % Liq. The measured values of variance were 95, 87.5, 80, 72, and 65 meV for 0, 15, 33, 50, and 100 wt. % Liq doped Alq 3 respectively. The increase in electron mobility upon doping has been attributed to a decrease in energetic disorder upon doping as evidenced by the decrease in variance. The increase in barrier height for the higher doping concentration was due to the disorder related correction r 2 /2kT in the barrier height, which decreases with the increase in doping concentration.

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Electron mobility in tris(8-hydroxyquinoline)aluminum (Alq3) films by transient electroluminescence from single layer organic light emitting diodes

Cited by 53 publications

References 21 publications

Transient electroluminescence spikes in small molecular organic light-emitting diodes

Transient electroluminescence spikes in small molecular organic light-emitting diodes

Studies on dynamics of charge carrier in organic electroluminescent devices

Effect of doping of 8-hydroxyquinolinatolithium on electron transport in tris(8-hydroxyquinolinato)aluminum

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