We report on the fabrication of plasma damage-free organic light-emitting devices (OLEDs) by usin... more We report on the fabrication of plasma damage-free organic light-emitting devices (OLEDs) by using a mirror shape target sputtering (MSTS) technique. It is shown that OLEDs with Al cathode deposited by the MSTS show much lower leakage current (1×10-5mA/cm2) at reverse bias of -6V, compared to that (1×10-1-˜10-2mA/cm2 at -6V) of OLEDs with Al cathodes grown by conventional dc magnetron sputtering. This indicates that there is no plasma damage, which is caused by the bombardment of energetic particles. This suggests that MSTS could be a useful plasma damage-free and low-temperature deposition technique for both top- and bottom-emitting OLEDs and flexible displays.
... Seung Hyun JI 2 and Young Soo YOON 2Ã ... caused by native defects such as oxygen vacancies a... more ... Seung Hyun JI 2 and Young Soo YOON 2Ã ... caused by native defects such as oxygen vacancies and zinc interstitials.9) Sheng et al.10) fabricated a Schottky diode using Ag on ð11 20Þ ZnO and reported an SBH of Ag (0.89 and 0.92eV) with a leakage current of 0.1nA at a 1V ...
The characteristics of a SiN x passivation layer grown by a specially designed catalyzer-enhanced... more The characteristics of a SiN x passivation layer grown by a specially designed catalyzer-enhanced chemical vapor deposition ͑CECVD͒ system for top-emitting organic light-emitting diodes ͑TOLEDs͒ were investigated. Using a tungsten catalyzer connected in series, a high-density SiN x passivation layer with high transmittance was deposited on TOLEDs at a substrate temperature of 50°C. Even at low substrate temperature, 150 nm thick SiN x passivation layer prepared by CECVD exhibited a low water vapor transmission rate of 2-6 ϫ 10 −2 g/m 2 /day. In addition, it was found that the transmittance of SiN x film at 550 nm was significantly influenced by the hydrogen flow rate. Current density-voltage-luminescence results of TOLEDs passivated with a 150 nm thick SiN x film indicated that the electrical and optical properties of TOLEDs were not affected by the high temperature tungsten catalyzer during the SiN x deposition. The lifetime to half initial luminance of a TOLED passivated with a 150 nm thick SiN x layer was much longer than that of a nonpassivated reference sample. This shows that the CECVD is a promising plasma free thin-film passivation technique for high-performance TOLEDs and flexible displays.
The preparation and characteristics of a transparent conducting indium zinc tin oxide ͑IZTO͒ anod... more The preparation and characteristics of a transparent conducting indium zinc tin oxide ͑IZTO͒ anode for highly efficient phosphorescent organic light emitting diodes ͑OLEDs͒ is described. The resistivity and transmittance of the IZTO anode are comparable to reference In 2 O 3 ͑ITO͒ anode films even though it was prepared at room temperature. In addition, the work function of the ozone-treated amorphous IZTO anode ͑5.12 ± 0.02 eV͒ is much higher than that of ozone-treated reference ITO anodes ͑4.94 ± 0.02 eV͒. The current-voltage-luminance characteristics and efficiencies of OLEDs prepared on the IZTO anode are critically dependent on the sheet resistance of the IZTO anode. Furthermore, both the quantum efficiency and power efficiency of the OLED fabricated on the amorphous IZTO anode are much higher than those of an OLED with the reference ITO anode due to the higher work function of the IZTO anode than those of conventional ITO anode. This indicates that IZTO is an alternative material for conventional ITO anodes used in OLEDs and flexible displays.
The series resistance of organic photovoltaic ͑OPV͒ devices was decreased by reducing the sheet r... more The series resistance of organic photovoltaic ͑OPV͒ devices was decreased by reducing the sheet resistance ͑R sh ͒ of the indium tin oxide ͑ITO͒ electrode, which leads to increasing device efficiency. The performance of bulk heterojunction OPVs was critically dependent on R sh of the ITO electrode. Upon reducing R sh of the ITO from 39 to 8.5 ⍀/ᮀ, the fill factor and power conversion efficiency of OPV was improved ͑from 0.407 to 0.580 and from 1.63 Ϯ 0.2 to 2.5 Ϯ 0.1%, respectively͒ under an AM1.5 simulated solar intensity of 100 mW/cm 2 . The dependence of the series resistance on R sh of the ITO suggests the dominance of the bulk resistance of the ITO electrode as a limiting factor in practical cell efficiencies.
We have investigated nonalloyed Al/Pt ohmic contacts on n-type ZnO:Al (n d ϭ2.0ϫ10 18 cm Ϫ3 ). It... more We have investigated nonalloyed Al/Pt ohmic contacts on n-type ZnO:Al (n d ϭ2.0ϫ10 18 cm Ϫ3 ). It is shown that the as-deposited Al/Pt contacts produce a specific contact resistivity of 1.2 ϫ10 Ϫ5 ⍀ cm 2 . Auger electron spectroscopy and x-ray photoelectron spectroscopy depth profile results show interdiffusion between oxygen and aluminum, resulting in an increase of carrier concentrations near the ZnO surface. The increase of the carrier concentration at the surface region of ZnO is attributed to the low resistance of the nonalloyed Al/Pt contact.
Abstract We report on a promising metallisation scheme for high-quality ohmic contacts to n-ZnO: ... more Abstract We report on a promising metallisation scheme for high-quality ohmic contacts to n-ZnO: Al (nd= 3× 10 18 cm-3. The as-deposited contact yields a specific contact resistance of 2.1× 10-3 Omega {\ cdot} cm 2. However, annealing of the contact at 700 C for 1 min ...
Dry etching processes for bulk-single crystal zinc oxide ͑ZnO͒ and molecular beam epitaxy ͑MBE͒ g... more Dry etching processes for bulk-single crystal zinc oxide ͑ZnO͒ and molecular beam epitaxy ͑MBE͒ grown ZnO have been investigated using inductively coupled plasma ͑ICP͒ of CH 4 and SiCl 4 based plasma chemistry. The CH 4 -based chemistry showed a higher etch rate than the SiCl 4 based chemistry, presumably due to the formation of highly volatile metal organic zinc compound. The influence of base pressure, radio frequency table power, and ICP power on etch rate was studied. Auger electron spectroscopy has been employed to examine the surface stoichiometry of etched ZnO using both plasma chemistries. Furthermore, with optimized process parameters, the effect of plasma etching on the optical properties of MBE grown ZnO film is studied. An enhancement of the band edge luminescence along with almost complete suppression of defect level luminescence in hydrogen-containing plasma treated ZnO film has been observed.
We prepared a nanoscale Ag-layer-inserted Ga-doped ZnO ͑GZO͒ multilayer on a flexible poly͑ether ... more We prepared a nanoscale Ag-layer-inserted Ga-doped ZnO ͑GZO͒ multilayer on a flexible poly͑ether sulfone͒ ͑PES͒ substrate using a continuous roll-to-roll ͑RTR͒ sputtering system at room temperature for the fabrication of highly flexible and transparent conducting oxide electrodes. When the thickness of the Ag interlayer was optimized ͑12 nm͒, the resulting GZO/Ag/GZO ͑GAG͒ multilayer showed a resistivity of 5.58 ϫ 10 −5 ⍀ cm and a transparency of 87.2% without in situ or ex situ annealing processes. However, although it exhibited lower resistivity, the GAG multilayer showed decreased optical transparency above the critical Ag interlayer thickness of 12 nm due to severe light scattering caused by the Ag layer. The results of bending tests demonstrated that the GAG multilayer resistance ͑⌬R/R͒ varies depending on the bending radius of the sample during repeated bending cycles. The constant surface morphology and resistance of the GAG multilayer even after the performance of bending tests indicate that RTR sputter grown GAG multilayers are promising as flexible transparent conducting electrodes for use in cost-efficient flexible displays and photovoltaics.
ZnO thin lms and nanostructures were grown on Si substrates in a metal organic chemical vapor dep... more ZnO thin lms and nanostructures were grown on Si substrates in a metal organic chemical vapor deposition (MOCVD) process as a function of growth conditions including source ow rates and growth temperatures. ZnO thin lms with smooth surface morphology were grown in growth conditions with low zinc source ow rates and high growth temperatures. On the other hand, the surface morphology of thin lms became dramatically rough on increasing the ow rate of the zinc source, resulting in the formation of various kinds of nanostructures such as nanorods, nanotowers, and nanocactuses, depending on the MOCVD growth temperature. This result is mainly due to the strong tendency of ZnO toward a three-dimensional (3D) growth mode with higher ow rates of the zinc source in a MOCVD process, indicating that a route from thin lms to nanostructures relies on the 3D growth behavior of ZnO.
Transmission Electron Microscope Study of In Situ Polycrystalline Si Film Grown by Catalyzer-Enha... more Transmission Electron Microscope Study of In Situ Polycrystalline Si Film Grown by Catalyzer-Enhanced Chemical Vapor Deposition. [Journal of The Electrochemical Society 154, J73 (2007)]. Han-Ki Kim, Myung Soo Kim, Jeong-Woo Park, Woon Jo Cho. Abstract. ...
The thin-film passivation of organic light-emitting diodes ͑OLEDs͒ by a SiN x film grown by catal... more The thin-film passivation of organic light-emitting diodes ͑OLEDs͒ by a SiN x film grown by catalyzer-enhanced chemical vapor deposition was investigated. Using a tungsten catalyzer connected in series, a high-density SiN x passivation layer was deposited on OLEDs and bare polycarbonate ͑PC͒ substrates at a substrate temperature of 50°C. Despite the low substrate temperature, the single SiN x passivation layer, grown on the PC substrate, exhibited a low water vapor transmission rate of ͑2-6͒ ϫ 10 −2 g/m 2 / day and a high transmittance of 87%. In addition, current-voltage-luminescence results of an OLED passivated with a 150-nm-thick SiN x film compared to nonpassivated sample were identical indicating that the performance of an OLED is not critically affected by radiation from tungsten catalyzer during the SiN x deposition. Moreover, the lifetime to half initial luminance of an OLED passivated with the single 150-nm-thick SiN x layer was 2.5 times longer than that of a nonpassivated sample.
The preparation and characteristics of flexible indium tin oxide (ITO) electrodes grown on polyet... more The preparation and characteristics of flexible indium tin oxide (ITO) electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible organic solar cells are described. It was found that both electrical and optical properties of the flexible ITO electrode were critically dependent on the Ar/O 2 flow ratio in the continuous roll-to-roll sputter process. In spite of the low substrate temperature (o50 1C), we can obtain the flexible ITO electrode with a sheet resistance of 47.4 O/square and an average optical transmittance of 83.46% in the green region of 500-550 nm wavelength. Both X-ray diffraction and field emission scanning electron microscopy analysis results showed that all flexible ITO electrodes grown on the PET substrate were amorphous with a very smooth and featureless surface, regardless of the Ar/O 2 flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion-beam-treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet-cleaned PET substrates, due to an increased adhesion between the flexible ITO and the PET substrates. Furthermore, the flexible organic solar cell fabricated on the rollto-roll sputter-grown flexible ITO electrode at an optimized condition exhibited a power conversion efficiency of 1.88%. This indicates that the roll-to-roll sputtering technique is a promising continuous sputtering process in preparing flexible transparent electrodes for flexible solar cells or displays.
Inductively coupled plasma reactive ion etching ͑ICP-RIE͒ of ZrO 2 :H solid electrolyte films was... more Inductively coupled plasma reactive ion etching ͑ICP-RIE͒ of ZrO 2 :H solid electrolyte films was investigated using BCl 3 -based plasma. ZrO 2 :H etch rates were studied as a function of the BCl 3 /Ar chemistry, ICP coil power, bias voltage, and working pressure. Scanning electron microscopy and atomic force microscopy were employed to characterize the etch rate and root-mean-square surface roughness of etched samples. It was found that in comparison with Cl 2 -based gas mixtures, pure BCl 3 plasma results in a high etch rate of ZrO 2 :H layer, suggesting an abundance of B and BCl radicals made up of a volatile compound such as B x O y , BCl-O, and Zr-Cl bond. In addition, Auger electron spectroscopy analysis exhibits that the BCl 3 -based etching process produces no change in surface stoichiometry of the ZrO 2 :H films.
We demonstrate a high-performance flexible organic light-emitting diode ͑OLED͒ employing amorphou... more We demonstrate a high-performance flexible organic light-emitting diode ͑OLED͒ employing amorphous indium zinc oxide ͑IZO͒ anode. The amorphous IZO on flexible polycarbonate ͑PC͒ substrate shows similar electrical conductivity and optical transmittance with commercial ͑ITO͒ glass, even though it was prepared at Ͻ50°C. Moreover, it exhibits little resistance change during 5000 bending cycles, demonstrating good mechanical robustness. A green phosphorescent OLED fabricated on amorphous IZO on flexible PC shows maximum external quantum efficiency of ext = 13.7% and power efficiency of p = 32.7 lm/W, which are higher than a device fabricated on a commercial ITO on glass ͑ ext = 12.4% and p = 30.1 lm/W͒ and ITO on flexible PC ͑ ext = 8.5% and p =14.1 lm/W͒. The mechanical robustness and low-temperature deposition of IZO combined with high OLED performance clearly manifest that the amorphous IZO is a promising anode material for flexible displays.
... Jae-Kwan Kim, Jun Young Kim, Seung-Cheol Han, Joon Seop Kwak, Han-Ki Kim, Ji ... and atomic c... more ... Jae-Kwan Kim, Jun Young Kim, Seung-Cheol Han, Joon Seop Kwak, Han-Ki Kim, Ji ... and atomic concentration of the etched surface by SEM and energy-dispersive X-ray analysis (EDX ... REPresley, D.Hong, HQChiang, CMHung, RLHoffman, and JFWager, Solid-State Electron., 50 ...
The characteristics of an SiN x passivation layer grown by a specially designed inductively coupl... more The characteristics of an SiN x passivation layer grown by a specially designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system with straight antennas for the top-emitting organic light emitting diodes (TOLEDs) are investigated. Using a high-density plasma on the order of ∼ 10 11 electrons/cm 3 formed by nine straight antennas connected in parallel, a high-density SiN x passivation layer was deposited on a transparent Mg-Ag cathode at a substrate temperature of 40°C. Even at a low substrate temperature, single SiN x passivation layer prepared by ICP-CVD showed a low water vapor transmission rate of 5 × 10 − 2 g/m 2 /day and a transparency of ∼ 85% respectively. In addition, currentvoltage-luminescence results of the TOLED passivated by the SiN x layer indicated that the electrical and optical properties of the TOLED were not affected by the high-density plasma during the SiN x deposition process.
We report on the fabrication of plasma damage-free organic light-emitting devices (OLEDs) by usin... more We report on the fabrication of plasma damage-free organic light-emitting devices (OLEDs) by using a mirror shape target sputtering (MSTS) technique. It is shown that OLEDs with Al cathode deposited by the MSTS show much lower leakage current (1×10-5mA/cm2) at reverse bias of -6V, compared to that (1×10-1-˜10-2mA/cm2 at -6V) of OLEDs with Al cathodes grown by conventional dc magnetron sputtering. This indicates that there is no plasma damage, which is caused by the bombardment of energetic particles. This suggests that MSTS could be a useful plasma damage-free and low-temperature deposition technique for both top- and bottom-emitting OLEDs and flexible displays.
... Seung Hyun JI 2 and Young Soo YOON 2Ã ... caused by native defects such as oxygen vacancies a... more ... Seung Hyun JI 2 and Young Soo YOON 2Ã ... caused by native defects such as oxygen vacancies and zinc interstitials.9) Sheng et al.10) fabricated a Schottky diode using Ag on ð11 20Þ ZnO and reported an SBH of Ag (0.89 and 0.92eV) with a leakage current of 0.1nA at a 1V ...
The characteristics of a SiN x passivation layer grown by a specially designed catalyzer-enhanced... more The characteristics of a SiN x passivation layer grown by a specially designed catalyzer-enhanced chemical vapor deposition ͑CECVD͒ system for top-emitting organic light-emitting diodes ͑TOLEDs͒ were investigated. Using a tungsten catalyzer connected in series, a high-density SiN x passivation layer with high transmittance was deposited on TOLEDs at a substrate temperature of 50°C. Even at low substrate temperature, 150 nm thick SiN x passivation layer prepared by CECVD exhibited a low water vapor transmission rate of 2-6 ϫ 10 −2 g/m 2 /day. In addition, it was found that the transmittance of SiN x film at 550 nm was significantly influenced by the hydrogen flow rate. Current density-voltage-luminescence results of TOLEDs passivated with a 150 nm thick SiN x film indicated that the electrical and optical properties of TOLEDs were not affected by the high temperature tungsten catalyzer during the SiN x deposition. The lifetime to half initial luminance of a TOLED passivated with a 150 nm thick SiN x layer was much longer than that of a nonpassivated reference sample. This shows that the CECVD is a promising plasma free thin-film passivation technique for high-performance TOLEDs and flexible displays.
The preparation and characteristics of a transparent conducting indium zinc tin oxide ͑IZTO͒ anod... more The preparation and characteristics of a transparent conducting indium zinc tin oxide ͑IZTO͒ anode for highly efficient phosphorescent organic light emitting diodes ͑OLEDs͒ is described. The resistivity and transmittance of the IZTO anode are comparable to reference In 2 O 3 ͑ITO͒ anode films even though it was prepared at room temperature. In addition, the work function of the ozone-treated amorphous IZTO anode ͑5.12 ± 0.02 eV͒ is much higher than that of ozone-treated reference ITO anodes ͑4.94 ± 0.02 eV͒. The current-voltage-luminance characteristics and efficiencies of OLEDs prepared on the IZTO anode are critically dependent on the sheet resistance of the IZTO anode. Furthermore, both the quantum efficiency and power efficiency of the OLED fabricated on the amorphous IZTO anode are much higher than those of an OLED with the reference ITO anode due to the higher work function of the IZTO anode than those of conventional ITO anode. This indicates that IZTO is an alternative material for conventional ITO anodes used in OLEDs and flexible displays.
The series resistance of organic photovoltaic ͑OPV͒ devices was decreased by reducing the sheet r... more The series resistance of organic photovoltaic ͑OPV͒ devices was decreased by reducing the sheet resistance ͑R sh ͒ of the indium tin oxide ͑ITO͒ electrode, which leads to increasing device efficiency. The performance of bulk heterojunction OPVs was critically dependent on R sh of the ITO electrode. Upon reducing R sh of the ITO from 39 to 8.5 ⍀/ᮀ, the fill factor and power conversion efficiency of OPV was improved ͑from 0.407 to 0.580 and from 1.63 Ϯ 0.2 to 2.5 Ϯ 0.1%, respectively͒ under an AM1.5 simulated solar intensity of 100 mW/cm 2 . The dependence of the series resistance on R sh of the ITO suggests the dominance of the bulk resistance of the ITO electrode as a limiting factor in practical cell efficiencies.
We have investigated nonalloyed Al/Pt ohmic contacts on n-type ZnO:Al (n d ϭ2.0ϫ10 18 cm Ϫ3 ). It... more We have investigated nonalloyed Al/Pt ohmic contacts on n-type ZnO:Al (n d ϭ2.0ϫ10 18 cm Ϫ3 ). It is shown that the as-deposited Al/Pt contacts produce a specific contact resistivity of 1.2 ϫ10 Ϫ5 ⍀ cm 2 . Auger electron spectroscopy and x-ray photoelectron spectroscopy depth profile results show interdiffusion between oxygen and aluminum, resulting in an increase of carrier concentrations near the ZnO surface. The increase of the carrier concentration at the surface region of ZnO is attributed to the low resistance of the nonalloyed Al/Pt contact.
Abstract We report on a promising metallisation scheme for high-quality ohmic contacts to n-ZnO: ... more Abstract We report on a promising metallisation scheme for high-quality ohmic contacts to n-ZnO: Al (nd= 3× 10 18 cm-3. The as-deposited contact yields a specific contact resistance of 2.1× 10-3 Omega {\ cdot} cm 2. However, annealing of the contact at 700 C for 1 min ...
Dry etching processes for bulk-single crystal zinc oxide ͑ZnO͒ and molecular beam epitaxy ͑MBE͒ g... more Dry etching processes for bulk-single crystal zinc oxide ͑ZnO͒ and molecular beam epitaxy ͑MBE͒ grown ZnO have been investigated using inductively coupled plasma ͑ICP͒ of CH 4 and SiCl 4 based plasma chemistry. The CH 4 -based chemistry showed a higher etch rate than the SiCl 4 based chemistry, presumably due to the formation of highly volatile metal organic zinc compound. The influence of base pressure, radio frequency table power, and ICP power on etch rate was studied. Auger electron spectroscopy has been employed to examine the surface stoichiometry of etched ZnO using both plasma chemistries. Furthermore, with optimized process parameters, the effect of plasma etching on the optical properties of MBE grown ZnO film is studied. An enhancement of the band edge luminescence along with almost complete suppression of defect level luminescence in hydrogen-containing plasma treated ZnO film has been observed.
We prepared a nanoscale Ag-layer-inserted Ga-doped ZnO ͑GZO͒ multilayer on a flexible poly͑ether ... more We prepared a nanoscale Ag-layer-inserted Ga-doped ZnO ͑GZO͒ multilayer on a flexible poly͑ether sulfone͒ ͑PES͒ substrate using a continuous roll-to-roll ͑RTR͒ sputtering system at room temperature for the fabrication of highly flexible and transparent conducting oxide electrodes. When the thickness of the Ag interlayer was optimized ͑12 nm͒, the resulting GZO/Ag/GZO ͑GAG͒ multilayer showed a resistivity of 5.58 ϫ 10 −5 ⍀ cm and a transparency of 87.2% without in situ or ex situ annealing processes. However, although it exhibited lower resistivity, the GAG multilayer showed decreased optical transparency above the critical Ag interlayer thickness of 12 nm due to severe light scattering caused by the Ag layer. The results of bending tests demonstrated that the GAG multilayer resistance ͑⌬R/R͒ varies depending on the bending radius of the sample during repeated bending cycles. The constant surface morphology and resistance of the GAG multilayer even after the performance of bending tests indicate that RTR sputter grown GAG multilayers are promising as flexible transparent conducting electrodes for use in cost-efficient flexible displays and photovoltaics.
ZnO thin lms and nanostructures were grown on Si substrates in a metal organic chemical vapor dep... more ZnO thin lms and nanostructures were grown on Si substrates in a metal organic chemical vapor deposition (MOCVD) process as a function of growth conditions including source ow rates and growth temperatures. ZnO thin lms with smooth surface morphology were grown in growth conditions with low zinc source ow rates and high growth temperatures. On the other hand, the surface morphology of thin lms became dramatically rough on increasing the ow rate of the zinc source, resulting in the formation of various kinds of nanostructures such as nanorods, nanotowers, and nanocactuses, depending on the MOCVD growth temperature. This result is mainly due to the strong tendency of ZnO toward a three-dimensional (3D) growth mode with higher ow rates of the zinc source in a MOCVD process, indicating that a route from thin lms to nanostructures relies on the 3D growth behavior of ZnO.
Transmission Electron Microscope Study of In Situ Polycrystalline Si Film Grown by Catalyzer-Enha... more Transmission Electron Microscope Study of In Situ Polycrystalline Si Film Grown by Catalyzer-Enhanced Chemical Vapor Deposition. [Journal of The Electrochemical Society 154, J73 (2007)]. Han-Ki Kim, Myung Soo Kim, Jeong-Woo Park, Woon Jo Cho. Abstract. ...
The thin-film passivation of organic light-emitting diodes ͑OLEDs͒ by a SiN x film grown by catal... more The thin-film passivation of organic light-emitting diodes ͑OLEDs͒ by a SiN x film grown by catalyzer-enhanced chemical vapor deposition was investigated. Using a tungsten catalyzer connected in series, a high-density SiN x passivation layer was deposited on OLEDs and bare polycarbonate ͑PC͒ substrates at a substrate temperature of 50°C. Despite the low substrate temperature, the single SiN x passivation layer, grown on the PC substrate, exhibited a low water vapor transmission rate of ͑2-6͒ ϫ 10 −2 g/m 2 / day and a high transmittance of 87%. In addition, current-voltage-luminescence results of an OLED passivated with a 150-nm-thick SiN x film compared to nonpassivated sample were identical indicating that the performance of an OLED is not critically affected by radiation from tungsten catalyzer during the SiN x deposition. Moreover, the lifetime to half initial luminance of an OLED passivated with the single 150-nm-thick SiN x layer was 2.5 times longer than that of a nonpassivated sample.
The preparation and characteristics of flexible indium tin oxide (ITO) electrodes grown on polyet... more The preparation and characteristics of flexible indium tin oxide (ITO) electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible organic solar cells are described. It was found that both electrical and optical properties of the flexible ITO electrode were critically dependent on the Ar/O 2 flow ratio in the continuous roll-to-roll sputter process. In spite of the low substrate temperature (o50 1C), we can obtain the flexible ITO electrode with a sheet resistance of 47.4 O/square and an average optical transmittance of 83.46% in the green region of 500-550 nm wavelength. Both X-ray diffraction and field emission scanning electron microscopy analysis results showed that all flexible ITO electrodes grown on the PET substrate were amorphous with a very smooth and featureless surface, regardless of the Ar/O 2 flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion-beam-treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet-cleaned PET substrates, due to an increased adhesion between the flexible ITO and the PET substrates. Furthermore, the flexible organic solar cell fabricated on the rollto-roll sputter-grown flexible ITO electrode at an optimized condition exhibited a power conversion efficiency of 1.88%. This indicates that the roll-to-roll sputtering technique is a promising continuous sputtering process in preparing flexible transparent electrodes for flexible solar cells or displays.
Inductively coupled plasma reactive ion etching ͑ICP-RIE͒ of ZrO 2 :H solid electrolyte films was... more Inductively coupled plasma reactive ion etching ͑ICP-RIE͒ of ZrO 2 :H solid electrolyte films was investigated using BCl 3 -based plasma. ZrO 2 :H etch rates were studied as a function of the BCl 3 /Ar chemistry, ICP coil power, bias voltage, and working pressure. Scanning electron microscopy and atomic force microscopy were employed to characterize the etch rate and root-mean-square surface roughness of etched samples. It was found that in comparison with Cl 2 -based gas mixtures, pure BCl 3 plasma results in a high etch rate of ZrO 2 :H layer, suggesting an abundance of B and BCl radicals made up of a volatile compound such as B x O y , BCl-O, and Zr-Cl bond. In addition, Auger electron spectroscopy analysis exhibits that the BCl 3 -based etching process produces no change in surface stoichiometry of the ZrO 2 :H films.
We demonstrate a high-performance flexible organic light-emitting diode ͑OLED͒ employing amorphou... more We demonstrate a high-performance flexible organic light-emitting diode ͑OLED͒ employing amorphous indium zinc oxide ͑IZO͒ anode. The amorphous IZO on flexible polycarbonate ͑PC͒ substrate shows similar electrical conductivity and optical transmittance with commercial ͑ITO͒ glass, even though it was prepared at Ͻ50°C. Moreover, it exhibits little resistance change during 5000 bending cycles, demonstrating good mechanical robustness. A green phosphorescent OLED fabricated on amorphous IZO on flexible PC shows maximum external quantum efficiency of ext = 13.7% and power efficiency of p = 32.7 lm/W, which are higher than a device fabricated on a commercial ITO on glass ͑ ext = 12.4% and p = 30.1 lm/W͒ and ITO on flexible PC ͑ ext = 8.5% and p =14.1 lm/W͒. The mechanical robustness and low-temperature deposition of IZO combined with high OLED performance clearly manifest that the amorphous IZO is a promising anode material for flexible displays.
... Jae-Kwan Kim, Jun Young Kim, Seung-Cheol Han, Joon Seop Kwak, Han-Ki Kim, Ji ... and atomic c... more ... Jae-Kwan Kim, Jun Young Kim, Seung-Cheol Han, Joon Seop Kwak, Han-Ki Kim, Ji ... and atomic concentration of the etched surface by SEM and energy-dispersive X-ray analysis (EDX ... REPresley, D.Hong, HQChiang, CMHung, RLHoffman, and JFWager, Solid-State Electron., 50 ...
The characteristics of an SiN x passivation layer grown by a specially designed inductively coupl... more The characteristics of an SiN x passivation layer grown by a specially designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system with straight antennas for the top-emitting organic light emitting diodes (TOLEDs) are investigated. Using a high-density plasma on the order of ∼ 10 11 electrons/cm 3 formed by nine straight antennas connected in parallel, a high-density SiN x passivation layer was deposited on a transparent Mg-Ag cathode at a substrate temperature of 40°C. Even at a low substrate temperature, single SiN x passivation layer prepared by ICP-CVD showed a low water vapor transmission rate of 5 × 10 − 2 g/m 2 /day and a transparency of ∼ 85% respectively. In addition, currentvoltage-luminescence results of the TOLED passivated by the SiN x layer indicated that the electrical and optical properties of the TOLED were not affected by the high-density plasma during the SiN x deposition process.
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