New insights on traps states in organic semiconductor applying illumination-free transient current method

Hirwa, Hippolyte; Wagner, Veit

doi:10.1016/j.orgel.2015.06.025

Cited by 9 publications

(6 citation statements)

References 25 publications

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“…At higher voltages, the OLED with electrospun cathodes, presents a saturation effect, meaning a higher trapping effect on either shallow or deep levels, which effectively reduces the electroluminescent effects [ 25 ]. This region is also known as a volume-controlled current with partly filled traps [ 26 ].…”

Section: Resultsmentioning

confidence: 99%

Organic Light-Emitting Diodes with Electrospun Electrodes for Double-Side Emissions

et al. 2023

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Transparent conductive electrodes (TCE) obtained by the electrospinning method and gold covered were used as cathodes in the organic light-emitting diodes (OLEDs) to create double side-emission. The electro-active nanofibers of poly(methyl methacrylate) (PMMA) with diameters in the range of several hundreds of nanometers, were prepared through the electrospinning method. The nanofibers were coated with gold by sputtering deposition, maintaining optimal transparency and conductivity to increase the electroluminescence on both electrodes. Optical, structural, and electrical measurements of the as-prepared transparent electrodes have shown good transparency and higher electrical conductivity. In this study, two types of OLEDs consisting of indium tin oxide (ITO)/ poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS)/ Ir(III) complex (8-hydroxyquinolinat bis(2-phenylpyridyl) iridium–IrQ(ppy)2 20 wt% embedded in N, N′-Dicarbazolyl-4,4′-biphenyl (CBP) sandwich structure and either gold-covered PMMA electrospun nanoweb (OLED with electrospun cathode) were fabricated together with a similar structure containing thin film gold cathodes (OLED with thin film cathode). The luminance-current-voltage characteristics, the capacitance-voltage, and the electroluminescence properties of these OLEDs were investigated.

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Section: Resultsmentioning

confidence: 99%

Organic Light-Emitting Diodes with Electrospun Electrodes for Double-Side Emissions

et al. 2023

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“…1a , the turn-on voltage of the three devices is about 3 V. It is relevant to the maximum of the first peak in their capacitance–voltage characteristics, indicating that it makes no difference to the turn-on voltage without AML in D 1 [ 9 – 11 ]. Figure 1b shows the current density–voltage (J-V) characteristics of the three devices in log–log scale, we divide the J-V curves into three regions, (I) leakage or diffusion-limited current caused by Ohmic contact, (II) volume-controlled current with an exponential distribution of traps, and (III) volume-controlled current with partly filled traps [ 20 ]. The higher current density of device D 3 at low applied voltage in region I may be attributed to the leakage current caused by the rough film morphology of solution-processed PEDOT:PSS films.…”

Section: Resultsmentioning

confidence: 99%

Efficient Trilayer Phosphorescent Organic Light-Emitting Devices Without Electrode Modification Layer and Its Working Mechanism

et al. 2018

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At present, numerous functional layers are introduced to improve the carrier injection and balance the carrier transport in organic light-emitting devices (OLEDs). Although it may be a good way to enhance the efficiency of devices, the introduction of functional layers would also result in extra process and long manufacture period. Actually, with the enrichment of material system, many appropriate materials could be chosen to share two or even more functions in OLEDs. Here, via impedance spectroscopy and transient electroluminescence analysis, di-[4-(N,N-ditolyl-amino)-phenyl] cyclohexane (TAPC) and 4,7-diphenyl-1,10-phenanthroline (Bphen) are demonstrated to serve as carrier injection and transport layers simultaneously. As a result, efficient trilayer OLEDs are achieved with comparable performances to conventional multilayer devices. Further studies have also been carried out to analyze the recombination and quenching mechanisms in devices. TAPC can block electrons effectively, while Bphen avoids the accumulation of holes. It makes carriers in emitting layer become more balanced, resulting in the reduction of efficiency roll-off.

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“…Investigation has also shown that by increasing the PCBM content electron extraction becomes better. This microscopic morphology model could be used in interpretation of macroscopic experiments such as charge extraction by linearly increasing voltage (CELIV) measurements on diodes or metal–insulator–semiconductor structures (MISCELIV measurements) or general transient current measurements. − Finally, for large PCBM contents (1:3 blend), the solar cells performances become limited by the light absorption and not by charge extraction.…”

Section: Discussionmentioning

confidence: 99%

Determining Material-Specific Morphology of Bulk-Heterojunction Organic Solar Cells Using AFM Phase Imaging

et al. 2017

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A technique for determining the materialspecific morphology of a polymer−fullerene blend is presented. This technique is applied to solution processed bulk-heterojunction organic solar cells with different weight ratios of polymer−fullerene blend using the PTB7:PCBM material system. Optical and electrical characterizations show that the light absorption increases for larger polymer (PTB7) content, while the fill factor of the fabricated solar cells is improved for larger fullerene (PCBM) content. The materialspecific morphologies of polymer−fullerene bulk-heterojunctions are measured by employing AFM phase imaging. The measured AFM phase images reveal that fullerene material forms flake-like clusters which are embedded in the polymer network. The size of the flakes is increasing with larger content of fullerene material. By correlating the optical and electrical properties with the measured bulk-heterojunction morphologies, the relation between bulk-heterojunction structure and solar cell performances is discussed.

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New insights on traps states in organic semiconductor applying illumination-free transient current method

Cited by 9 publications

References 25 publications

Organic Light-Emitting Diodes with Electrospun Electrodes for Double-Side Emissions

Organic Light-Emitting Diodes with Electrospun Electrodes for Double-Side Emissions

Efficient Trilayer Phosphorescent Organic Light-Emitting Devices Without Electrode Modification Layer and Its Working Mechanism

Determining Material-Specific Morphology of Bulk-Heterojunction Organic Solar Cells Using AFM Phase Imaging

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