Charge Injection Mechanisms in Solid State Organic Light-Emitting Devices Based on Alizarin Violet

Das, Sharmistha; Chowdhury, Avijit; Roy, S. R.; Pal, Amlan J.

doi:10.1002/1521-396x(200004)178:2<811::aid-pssa811>3.0.co;2-w

Cited by 7 publications

(5 citation statements)

References 15 publications

(10 reference statements)

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“…This means that the SCLC mechanism, shown by impedance spectroscopy for V > 1 V, could not be the main one. Several authors have shown [55,56], for PVK sandwich structures, that in the low field domain, thermionic emission can occur. This is presently verified over a broad voltage domain, as shown in the inset of figure 9 for 20% volume ratio of TiO 2 nanoparticles (the same behaviour is observed for 30 and 50%).…”

Section: Forward Biasmentioning

confidence: 99%

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO₂nanocomposites for solar cell applications

et al. 2008

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The photogeneration of charge carriers in spin-coated thin films of nanocrystalline (nc-)TiO(2) particles dispersed in a semiconducting polymer, poly(N-vinylcarbazole) (PVK), has been studied by photoluminescence and charge transport measurements. The solvent and the TiO(2) particle concentration have been selected to optimize the composite morphology. A large number of small domains leading to a large interface and an improved exciton dissociation could be obtained with tetrahydrofuran (THF). The charge transport mechanism and trap distribution at low and high voltage in ITO/nc-TiO(2):PVK/Al diodes in the dark could be identified by current-voltage measurements and impedance spectroscopy. The transport mechanism is space charge limited with an exponential trap distribution in the high voltage regime (1-4 V), whereas a Schottky process with a barrier height of about 0.9 eV is observed at low bias voltages (<1 V). The current-voltage characteristics under white illumination have shown a dramatic increase of the short circuit current density J(sc) and open circuit voltage V(oc) for a 30% TiO(2) volume content corresponding to the morphology exhibiting the best dispersion of TiO(2) particles. A degradation of the photovoltaic properties is induced at higher compositions by the formation of larger TiO(2) aggregates. A procedure has been developed to extract the physical parameters from the J-V characteristics in the dark and under illumination on the basis of an equivalent circuit. The variation of the solar cell parameters with the TiO(2) composition confirms that the photovoltaic response is optimum for 30% TiO(2) volume content. It is concluded that the photovoltaic properties of nc-TiO(2):PVK nanocomposites are controlled by the interfacial area between the donor and the acceptor material and are limited by the dispersion of the TiO(2) nanoparticles in the polymer.

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Section: Forward Biasmentioning

confidence: 99%

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO₂nanocomposites for solar cell applications

et al. 2008

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“…We first present our studies that have been obtained for different contacts/electrodes. By keeping electron-barrier height, e f , unchanged ͑0.7 eV͒, 17 we varied the hole-barrier height, h f , to study the EL profile. Figure 1 shows the dependence of EL f and EL r on h f .…”

Section: Resultsmentioning

confidence: 99%

“…Under forward bias, the barrier height for holes ( h f ) and electrons ( e f ) have been considered as 0.3 and 0.7 eV, respectively. 17 The lattice plane next to the ITO electrode is considered as zϭ0, while the one adjacent to Al is zϭz max .…”

Section: Model and Simulation Methodsmentioning

confidence: 99%

Monte Carlo simulation of organic light-emitting devices under alternating applied field

Paul

Pal

et al. 2003

Journal of Applied Physics

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A Monte Carlo method has been employed to simulate electroluminescence ͑EL͒ from organic light-emitting devices ͑LEDs͒ under an alternating applied field. EL responses under forward and reverse bias modes have been simulated with different experimental parameters. Dependences of EL on the frequency of an applied field, electrode work function, band gap and film thickness of the active organic material, etc., have been studied. The origin of EL under alternating current ͑ac͒ mode has been explained in terms of radiative recombination of excitons formed via injected holes and electrons present from the previous cycle of ac voltage. The time response of EL intensity and its profile during forward and reverse bias half-cycles has been found to depend on carrier injection and also on their temporal and spatial distribution along the thickness of the emitting material. Efforts have been made to match a simulated EL response with representative experimental results. The Monte Carlo simulation results presented here provides a way to select certain parameters to fabricate efficient ac LEDs.

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“…The barrier heights for holes and electrons were taken ͑as 0.4 and 0.6 eV, respectively͒ from our recent experimental results. 20 Hole-toelectron mobility ratio ( h / e ) and ␤ have been taken as 30 and 0.01, respectively. The similarity between the experiment and simulation primarily confirms the hypothesis we put forward in the transient response studies.…”

Section: Resultsmentioning

confidence: 99%

Transient response of organic light-emitting devices: A Monte Carlo simulation study

Das

Talapatra

Chowdhury

et al. 2000

Journal of Applied Physics

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A Monte Carlo simulation method has been conducted to study transient response of electroluminescence in single-layer light-emitting devices. The results from the numerical method have been compared with our recent (transient) experimental results. The simulation results supported the role and contribution of accumulated charges at the metal–semiconductor interfaces in device operation. Several parameters like barrier heights and mobilities of charge carriers, width and distribution of the accumulated space charge regions in the device, have been used in the simulation work. Additionally, barriers for charge injection have been considered to be modified by the presence of space charges near the injecting interfaces. A recipe has been established to estimate different parameters of device operation from the comparison between simulation and experimental results.

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Charge Injection Mechanisms in Solid State Organic Light-Emitting Devices Based on Alizarin Violet

Cited by 7 publications

References 15 publications

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO₂nanocomposites for solar cell applications

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO₂nanocomposites for solar cell applications

Monte Carlo simulation of organic light-emitting devices under alternating applied field

Transient response of organic light-emitting devices: A Monte Carlo simulation study

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Charge Injection Mechanisms in Solid State Organic Light-Emitting Devices Based on Alizarin Violet

Cited by 7 publications

References 15 publications

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO2nanocomposites for solar cell applications

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO2nanocomposites for solar cell applications

Monte Carlo simulation of organic light-emitting devices under alternating applied field

Transient response of organic light-emitting devices: A Monte Carlo simulation study

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Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO₂nanocomposites for solar cell applications

Investigation of exciton photodissociation, charge transport and photovoltaic response of poly(N-vinyl carbazole):TiO₂nanocomposites for solar cell applications