The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Yongli Gao - One of the best experts on this subject based on the ideXlab platform.
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interface analysis of naphthyl substituted Benzidine Derivative and tris 8 hydroxyquinoline aluminum using ultraviolet and x ray photoemission spectroscopy
Journal of Vacuum Science and Technology, 1999Co-Authors: Eric W Forsythe, Viene Choong, Yongli GaoAbstract:We have studied the interface between naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3). Ultraviolet photoemission and x-ray photoemission spectroscopy (UPS, XPS) are used to distinguish contributions from NPB and Alq3 and reveal an interface formation region of approximately one to two monolayers. The UPS results show the highest occupied molecular orbital (HOMO) level offset is 0.3 eV, whereas the lowest unoccupied molecular orbitial offset is 0.8 eV, which confines electrons in the emissive Alq3 layer of the heterostructure. From the UPS difference spectrum, the gradual modification of the HOMO levels are revealed. Within the interface region, the energy levels bend by more than 0.3 eV. The Alq3 and NPB HOMO level increases are consistent with the vacuum level shift as well as the observed core level shifts from XPS. Further, the XPS and UPS results show no chemical interactions or wave function overlap at the interface.
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Trap states in doped tris-8-(hydroxyquinoline) aluminum using thermally stimulated luminescence
Organic Light-Emitting Materials and Devices II, 1998Co-Authors: Eric Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The light emission from bi-layer organic devices (OLEDs) has been shown to be proportional to the current. Trap states have been speculated to contribute to the carrier transport in such devices. We will report on the bulk trap state properties of naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) using thermally stimulated luminescence (TSL). Using a general order TSL expression, the four peaks in NPB were modeled with trap sates centered from 0.15 eV to 0.02 eV. The main Alq3 peak is modeled as a distribution of trap states from 0.25 to 0.15 eV with two additional peaks observed at lower trap energies. For both materials, the trapping mechanism involves a combination of first and second order emission. Using TSL,the evolution of the trap states in Alq3 has been studied as a function of coumarin 6 and NPB doping,k with doping levels from 0.1 percent to 2.0 percent. For Alq3 doped with coumarin 6, we observe an almost 0.1 eV increase in the width of the trap states. Conversely, the Alq3 samples doped with NPB do not show a change in the trap states. These trap depths are sufficient to support a trap charge limited model for the carrier transport in bilayer organic based light emitting diodes.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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trap states of tris 8 hydroxyquinoline aluminum and naphthyl substituted Benzidine Derivative using thermally stimulated luminescence
Applied Physics Letters, 1998Co-Authors: Eric W Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The bulk trap state properties of a naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) have been measured using thermally stimulated luminescence (TSL). The TSL spectra for both organic materials show significant trap distributions over the temperature range from 8 to 300 K. Using a general order TSL expression, the four peaks in NPB were modeled with trap states centered from 0.20 to 0.05 eV. Alq3 has three TSL peaks over the temperature range, with the peak at 156 K modeled as a distribution of trap states from 0.25 to 0.13 eV. For both materials, the trapping mechanism involves a combination of first and second order emission. NPB and Alq3 have trap states sufficiently deep to influence the carrier transport and recombination process in bilayer organic based light emitting.
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Thermally Stimulated Luminescence of Naphthylsubstituted Benzidine Derivative and Triss-8s-(Hydroxyquinoline) Aluminum With and Without Metal Layers
MRS Online Proceedings Library, 1997Co-Authors: Eric W Forsythe, David C Morton, Yongli GaoAbstract:Multilayer organic light emitting devices based on triss-8s-(hydroxyquinoline) aluminum (Alq_3) and a naphthyl-substituted Benzidine Derivative (NPB) have demonstrated practical electroluminescence with a wide range of color. Trap states in these materials play an important role in the carrier transport as well as the light emission process. We report the first observation of thermally stimulated luminescence (TSL) from Alq_3 and NPB. The TSL spectra from 8 K to 300 K were used to determine the trap states in Alq_3 and NPB. The results for Alq_3 show a significant trap distribution at 156 K, which corresponds to a mean trap depth ranging from 0.18 to 0.12 eV, whereas the trap states in NPB are centered from 0.15 eV to 0.01 eV. We have used TSL to study the trap state properties of thin metal layers in the Alq_3 films. In addition, we report photoluminescence as a function of temperature for Alq_3. TSL spectroscopy provides a technique to study the trap states in a specific layer of the device structure.
Ching Wan Tang - One of the best experts on this subject based on the ideXlab platform.
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Trap states in doped tris-8-(hydroxyquinoline) aluminum using thermally stimulated luminescence
Organic Light-Emitting Materials and Devices II, 1998Co-Authors: Eric Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The light emission from bi-layer organic devices (OLEDs) has been shown to be proportional to the current. Trap states have been speculated to contribute to the carrier transport in such devices. We will report on the bulk trap state properties of naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) using thermally stimulated luminescence (TSL). Using a general order TSL expression, the four peaks in NPB were modeled with trap sates centered from 0.15 eV to 0.02 eV. The main Alq3 peak is modeled as a distribution of trap states from 0.25 to 0.15 eV with two additional peaks observed at lower trap energies. For both materials, the trapping mechanism involves a combination of first and second order emission. Using TSL,the evolution of the trap states in Alq3 has been studied as a function of coumarin 6 and NPB doping,k with doping levels from 0.1 percent to 2.0 percent. For Alq3 doped with coumarin 6, we observe an almost 0.1 eV increase in the width of the trap states. Conversely, the Alq3 samples doped with NPB do not show a change in the trap states. These trap depths are sufficient to support a trap charge limited model for the carrier transport in bilayer organic based light emitting diodes.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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trap states of tris 8 hydroxyquinoline aluminum and naphthyl substituted Benzidine Derivative using thermally stimulated luminescence
Applied Physics Letters, 1998Co-Authors: Eric W Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The bulk trap state properties of a naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) have been measured using thermally stimulated luminescence (TSL). The TSL spectra for both organic materials show significant trap distributions over the temperature range from 8 to 300 K. Using a general order TSL expression, the four peaks in NPB were modeled with trap states centered from 0.20 to 0.05 eV. Alq3 has three TSL peaks over the temperature range, with the peak at 156 K modeled as a distribution of trap states from 0.25 to 0.13 eV. For both materials, the trapping mechanism involves a combination of first and second order emission. NPB and Alq3 have trap states sufficiently deep to influence the carrier transport and recombination process in bilayer organic based light emitting.
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organic electroluminescent devices with improved stability
Applied Physics Letters, 1996Co-Authors: S A Van Slyke, Chinhsien Chen, Ching Wan TangAbstract:Highly stable organic electroluminescent devices based on vapor‐deposited Alq thin films have been achieved. The improvement in stability is derived from several factors including: (1) a multilayer thin‐film structure with a CuPc stabilized hole‐injection contact, (2) a hole‐transport diamine layer using a naphthyl‐substituted Benzidine Derivative, and (3) an ac drive wave form. These emissive devices have shown an operational half‐lifetime of about 4000 h from an initial luminance of 510 cd/m2.
Meiso Yokoyama - One of the best experts on this subject based on the ideXlab platform.
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Using [naphthyl-substituted Benzidine Derivative] (NPB) : Tris-(8-hydroxyquinoline)-aluminum(III) (Alq3) mixed Layer to improve the efficiency of organic light emitting diodes
Journal de Physique IV (Proceedings), 2006Co-Authors: Ching-huei Tseng, Uerng-yih Ueng, Meiso YokoyamaAbstract:The organic light emitting diodes (OLED) with a mixed layer has been prepared. The mixed layer is constructed by mixing tris-(8-hydroxyquinoline)-aluminum(III) (Alq 3 ) with [Naphthyl-substituted Benzidine Derivative] (NPB), and inserted it between the hole transporting layer of NPB and the emitting layer of Alq 3 . The structure of the mixed layer OLED is ITO/ [4',4"-tris[3-methylphenyl(phenyl) amino] triphenylamine (MTDATA)( 15 nm)/NPB(60-X nm)/NPB:Alq 3 (Y weight-%)(X nm)/Alq 3 (60 nm)/LiF/Al. In this study, the best concentration of Alq 3 in NPB is 30 wt% with the total thickness of 30 nm. The maximum luminescence efficiency is 9.0 cd/A.
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The exciplex emission of organic light emitting diodes with 5, 6, 11, 12-tetraphenylnaphthacene (Rubrene)-doped hole transport layer
Journal de Physique IV (Proceedings), 2006Co-Authors: Ching-huei Tseng, Uerng-yih Ueng, Meiso YokoyamaAbstract:Exciplex electroluminescence of indium-tin-oxide glass (ITO)/[4',4"-tris[3-methylphenyl (phenyl) amino]triphenylarnine](m-MTDATA)/[Naphthyl-substituted Benzidine Derivative] (NPB)/NPB: rubrene/BCP/LiF/Al devices have been investigated. The ITO/MTDATA/NPB/NPB:Rubrene/BCP/LiF/Al devices show emission color adiustable by the hybrid exciplex interaction of Rubrene with NPB, and this exciplex becomes the primary recombination center at a critical Rubrene doping concentration. We obtained its emission was green-white light and the green emission is exciplex emission of the binary-blend NPB:rubrene layer. It is demonstrated at the PL spectra.
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Using [Naphthyl-substituted Benzidine Derivative] (NPB): Tris-(8-hydroxyquinoline)-aluminum(III) (Alq$_{3}$) mixed Layer to improve the efficiency of organic light emitting diodes
EDP Sciences, 1Co-Authors: Ching-huei Tseng, Uerng-yih Ueng, Meiso YokoyamaAbstract:The organic light emitting diodes (OLED) with a mixed layer has been prepared. The mixed layer is constructed by mixing tris-(8-hydroxyquinoline)-aluminum(III) (Alq$_{3})$ with [Naphthyl-substituted Benzidine Derivative] (NPB), and inserted it between the hole transporting layer of NPB and the emitting layer of Alq$_{3}$. The structure of the mixed layer OLED is ITO/ [ $4^{\prime}$,$4^{\prime\prime}$-tris[3-methylphenyl(phenyl) amino] triphenylamine (MTDATA)(15 nm)/NPB(60-X nm)/NPB:Alq$_{3}$(Y weight-%)(X nm)/Alq$_{3}$(60 nm)/LiF/Al. In this study, the best concentration of Alq$_{3}$ in NPB is 30 wt% with the total thickness of 30 nm. The maximum luminescence efficiency is 9.0 cd/A
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The exciplex emission of organic light emitting diodes with 5, 6, 11, 12-tetraphenylnaphthacene (Rubrene)-doped hole transport layer
EDP Sciences, 1Co-Authors: Ching-huei Tseng, Uerng-yih Ueng, Meiso YokoyamaAbstract:Exciplex electroluminescence of indium-tin-oxide glass (ITO)/[ 4$^\prime$,4$^{\prime\prime}$-tris[3-methylphenyl (phenyl) amino]triphenylamine] (m-MTDATA)/[Naphthyl-substituted Benzidine Derivative] (NPB)/NPB:rubrene/BCP/LiF/Al devices have been investigated. The ITO/MTDATA/NPB/NPB:Rubrene/BCP/LiF/Al devices show emission color adiustable by the hybrid exciplex interaction of Rubrene with NPB, and this exciplex becomes the primary recombination center at a critical Rubrene doping concentration. We obtained its emission was green-white light and the green emission is exciplex emission of the binary-blend NPB:rubrene layer. It is demonstrated at the PL spectra
Eric W Forsythe - One of the best experts on this subject based on the ideXlab platform.
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interface analysis of naphthyl substituted Benzidine Derivative and tris 8 hydroxyquinoline aluminum using ultraviolet and x ray photoemission spectroscopy
Journal of Vacuum Science and Technology, 1999Co-Authors: Eric W Forsythe, Viene Choong, Yongli GaoAbstract:We have studied the interface between naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3). Ultraviolet photoemission and x-ray photoemission spectroscopy (UPS, XPS) are used to distinguish contributions from NPB and Alq3 and reveal an interface formation region of approximately one to two monolayers. The UPS results show the highest occupied molecular orbital (HOMO) level offset is 0.3 eV, whereas the lowest unoccupied molecular orbitial offset is 0.8 eV, which confines electrons in the emissive Alq3 layer of the heterostructure. From the UPS difference spectrum, the gradual modification of the HOMO levels are revealed. Within the interface region, the energy levels bend by more than 0.3 eV. The Alq3 and NPB HOMO level increases are consistent with the vacuum level shift as well as the observed core level shifts from XPS. Further, the XPS and UPS results show no chemical interactions or wave function overlap at the interface.
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trap states of tris 8 hydroxyquinoline aluminum and naphthyl substituted Benzidine Derivative using thermally stimulated luminescence
Applied Physics Letters, 1998Co-Authors: Eric W Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The bulk trap state properties of a naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) have been measured using thermally stimulated luminescence (TSL). The TSL spectra for both organic materials show significant trap distributions over the temperature range from 8 to 300 K. Using a general order TSL expression, the four peaks in NPB were modeled with trap states centered from 0.20 to 0.05 eV. Alq3 has three TSL peaks over the temperature range, with the peak at 156 K modeled as a distribution of trap states from 0.25 to 0.13 eV. For both materials, the trapping mechanism involves a combination of first and second order emission. NPB and Alq3 have trap states sufficiently deep to influence the carrier transport and recombination process in bilayer organic based light emitting.
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Thermally Stimulated Luminescence of Naphthylsubstituted Benzidine Derivative and Triss-8s-(Hydroxyquinoline) Aluminum With and Without Metal Layers
MRS Online Proceedings Library, 1997Co-Authors: Eric W Forsythe, David C Morton, Yongli GaoAbstract:Multilayer organic light emitting devices based on triss-8s-(hydroxyquinoline) aluminum (Alq_3) and a naphthyl-substituted Benzidine Derivative (NPB) have demonstrated practical electroluminescence with a wide range of color. Trap states in these materials play an important role in the carrier transport as well as the light emission process. We report the first observation of thermally stimulated luminescence (TSL) from Alq_3 and NPB. The TSL spectra from 8 K to 300 K were used to determine the trap states in Alq_3 and NPB. The results for Alq_3 show a significant trap distribution at 156 K, which corresponds to a mean trap depth ranging from 0.18 to 0.12 eV, whereas the trap states in NPB are centered from 0.15 eV to 0.01 eV. We have used TSL to study the trap state properties of thin metal layers in the Alq_3 films. In addition, we report photoluminescence as a function of temperature for Alq_3. TSL spectroscopy provides a technique to study the trap states in a specific layer of the device structure.
David C Morton - One of the best experts on this subject based on the ideXlab platform.
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Trap states in doped tris-8-(hydroxyquinoline) aluminum using thermally stimulated luminescence
Organic Light-Emitting Materials and Devices II, 1998Co-Authors: Eric Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The light emission from bi-layer organic devices (OLEDs) has been shown to be proportional to the current. Trap states have been speculated to contribute to the carrier transport in such devices. We will report on the bulk trap state properties of naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) using thermally stimulated luminescence (TSL). Using a general order TSL expression, the four peaks in NPB were modeled with trap sates centered from 0.15 eV to 0.02 eV. The main Alq3 peak is modeled as a distribution of trap states from 0.25 to 0.15 eV with two additional peaks observed at lower trap energies. For both materials, the trapping mechanism involves a combination of first and second order emission. Using TSL,the evolution of the trap states in Alq3 has been studied as a function of coumarin 6 and NPB doping,k with doping levels from 0.1 percent to 2.0 percent. For Alq3 doped with coumarin 6, we observe an almost 0.1 eV increase in the width of the trap states. Conversely, the Alq3 samples doped with NPB do not show a change in the trap states. These trap depths are sufficient to support a trap charge limited model for the carrier transport in bilayer organic based light emitting diodes.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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trap states of tris 8 hydroxyquinoline aluminum and naphthyl substituted Benzidine Derivative using thermally stimulated luminescence
Applied Physics Letters, 1998Co-Authors: Eric W Forsythe, Ching Wan Tang, David C Morton, Yongli GaoAbstract:The bulk trap state properties of a naphthyl-substituted Benzidine Derivative (NPB) and tris-8-(hydroxyquinoline) aluminum (Alq3) have been measured using thermally stimulated luminescence (TSL). The TSL spectra for both organic materials show significant trap distributions over the temperature range from 8 to 300 K. Using a general order TSL expression, the four peaks in NPB were modeled with trap states centered from 0.20 to 0.05 eV. Alq3 has three TSL peaks over the temperature range, with the peak at 156 K modeled as a distribution of trap states from 0.25 to 0.13 eV. For both materials, the trapping mechanism involves a combination of first and second order emission. NPB and Alq3 have trap states sufficiently deep to influence the carrier transport and recombination process in bilayer organic based light emitting.
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Thermally Stimulated Luminescence of Naphthylsubstituted Benzidine Derivative and Triss-8s-(Hydroxyquinoline) Aluminum With and Without Metal Layers
MRS Online Proceedings Library, 1997Co-Authors: Eric W Forsythe, David C Morton, Yongli GaoAbstract:Multilayer organic light emitting devices based on triss-8s-(hydroxyquinoline) aluminum (Alq_3) and a naphthyl-substituted Benzidine Derivative (NPB) have demonstrated practical electroluminescence with a wide range of color. Trap states in these materials play an important role in the carrier transport as well as the light emission process. We report the first observation of thermally stimulated luminescence (TSL) from Alq_3 and NPB. The TSL spectra from 8 K to 300 K were used to determine the trap states in Alq_3 and NPB. The results for Alq_3 show a significant trap distribution at 156 K, which corresponds to a mean trap depth ranging from 0.18 to 0.12 eV, whereas the trap states in NPB are centered from 0.15 eV to 0.01 eV. We have used TSL to study the trap state properties of thin metal layers in the Alq_3 films. In addition, we report photoluminescence as a function of temperature for Alq_3. TSL spectroscopy provides a technique to study the trap states in a specific layer of the device structure.