Showing papers by "Jin Young Oh published in 2013"
TL;DR: Th thin-film transistors (TFTs) with a solution-processed channel layer of indium zinc oxide (IZO) on a peroxo-zirconium oxide (ZrO(2)) dielectric with a maximum temperature of 350 °C are demonstrated and successfully blocked leakage current even in annealing at 300 °C.
Abstract: We demonstrated solution-processed thin film transistors on a peroxo-zirconium oxide (ZrO2) dielectric with a maximum temperature of 350 °C. The formation of ZrO2 films was investigated by TG-DTA, FT-IR, and XPS analyses at various temperatures. We synthesized a zirconium oxide solution by adding hydrogen peroxide (H2O2). The H2O2 forms peroxo groups in the ZrO2 film producing a dense-amorphous phase and a smooth surface film. Because of these characteristics, the ZrO2 film successfully blocked leakage current even in annealing at 300 °C. Finally, to demonstrate that the ZrO2 film is dielectric, we fabricated thin-film transistors (TFTs) with a solution-processed channel layer of indium zinc oxide (IZO) on ZrO2 films at 350 °C. These TFTs had a mobility of 7.21 cm2/(V s), a threshold voltage (Vth) of 3.22 V, and a Vth shift of 1.6 V under positive gate bias stress.
163 citations
TL;DR: The results suggest that aqueous solution-processed In2O3 TFTs on ZrO2:B dielectrics could potentially be used for low-cost, low-temperature, and high-performance flexible devices.
Abstract: We developed a solution-processed indium oxide (In2O3) thin-film transistor (TFT) with a boron-doped peroxo-zirconium (ZrO2:B) dielectric on silicon as well as polyimide substrate at 200 °C, using water as the solvent for the In2O3 precursor. The formation of In2O3 and ZrO2:B films were intensively studied by thermogravimetric differential thermal analysis (TG-DTA), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT IR), high-resolution X-ray diffraction (HR-XRD), and X-ray photoelectron spectroscopy (XPS). Boron was selected as a dopant to make a denser ZrO2 film. The ZrO2:B film effectively blocked the leakage current at 200 °C with high breakdown strength. To evaluate the ZrO2:B film as a gate dielectric, we fabricated In2O3 TFTs on the ZrO2:B dielectrics with silicon substrates and annealed the resulting samples at 200 and 250 °C. The resulting mobilities were 1.25 and 39.3 cm(2)/(V s), respectively. Finally, we realized a flexible In2O3 TFT with the ZrO2:B dielectric on a polyimide substrate at 200 °C, and it successfully operated a switching device with a mobility of 4.01 cm(2)/(V s). Our results suggest that aqueous solution-processed In2O3 TFTs on ZrO2:B dielectrics could potentially be used for low-cost, low-temperature, and high-performance flexible devices.
111 citations
TL;DR: A novel and easy strategy for fabricating solution-processed metal oxide thin-film transistors by controlling the dielectric constant of H2O through manipulation of the metal precursor solution temperature is reported, which means indium zinc oxide (IZO) thin- Film transistors fabricated from IZO solution at 4 °C can be operated after annealing at low temperatures.
Abstract: Herein, we report a novel and easy strategy for fabricating solution-processed metal oxide thin-film transistors by controlling the dielectric constant of H2O through manipulation of the metal precursor solution temperature. As a result, indium zinc oxide (IZO) thin-film transistors (TFTs) fabricated from IZO solution at 4 °C can be operated after annealing at low temperatures (∼250 °C). In contrast, IZO TFTs fabricated from IZO solutions at 25 and 60 °C must be annealed at 275 and 300 °C, respectively. We also found that IZO TFTs fabricated from the IZO precursor solution at 4 °C had the highest mobility of 12.65 cm2/(V s), whereas the IZO TFTs fabricated from IZO precursor solutions at 25 and 60 °C had field-effect mobility of 5.39 and 4.51 cm2/(V s), respectively, after annealing at 350 °C. When the IZO precursor solution is at 4 °C, metal cations such as indium (In3+) and zinc ions (Zn2+) can be fully surrounded by H2O molecules, because of the higher dielectric constant of H2O at lower temperatures. ...
42 citations
TL;DR: In this paper, the authors applied a C&H process with a P3HT/PCBM m-xylene solution to generate P3H:PCBM nanofibril composite films and found that the hole transport was 2.6 times faster in the thickness direction and 6.5 times more conductive in the in-plane direction.
Abstract: Applying conventional printing technologies to fabricate large-area flexible bulk heterojunction (BHJ) solar cells is of great interest. Achieving this task requires (i) large tolerance of the maximum photoconversion efficiency (PCE) to the film thickness, (ii) fast hole transport in both the thickness and lateral directions of the BHJ layer, and (iii) improved stability against bending and heat. This paper demonstrates that a P3HT:PCBM BHJ layer made of long P3HT nanofibrils of almost 100% crystallinity can be an excellent approach to achieve large-area printed solar cells. We applied a cool-and-heat (C&H) process with a P3HT/PCBM m-xylene solution to generate P3HT:PCBM nanofibril composite films. We found that the hole transport of the nanofibril composite was 2.6 times faster in the thickness direction and 6.5 times more conductive in the in-plane direction compared with conventionally annealed composites. The fast hole transport in the thickness direction led to negligible dependence of the PCE on the...
39 citations
TL;DR: In this article, the authors reported a 36% improvement in the performance of inverted solar cells as a result of increased shortcircuit current (JSC) obtained using a composition of zinc oxide (ZnO) and reduced graphene oxide (RGO) as an n-type buffer layer.
Abstract: In this study, we reported a 36% improvement in the performance of inverted solar cells as a result of increased short-circuit current (JSC) obtained using a composition of zinc oxide (ZnO) and reduced graphene oxide (RGO) as an n-type buffer layer. RGO-ZnO nanocomposites show higher electron conductivity than intrinsic ZnO; moreover, they show reduced contact resistance at the interface between the active layer and n-type buffer layer. These factors prevent carrier loss resulting from defects and recombinations in the device, thereby significantly increasing the JSC value for the device. Thus, an efficiency of 4.15% was achieved for inverted solar cells with a controlled RGO-ZnO nanocomposites layer.
35 citations
TL;DR: In this article, a strategy for the in line mass production of a 3D non-woven nanofabric consisting of crystalline P3HT nanofibrils, created by in situ cooling of the transportation line to feed a P3H solution for a coating tool, was introduced.
Abstract: A strategy for the in line mass production of a three-dimensional (3D) non-woven nanofabric consisting of crystalline P3HT nanofibrils, created by in situ cooling of the transportation line to feed a P3HT solution for a coating tool, was introduced. The required cooling-temperature with respect to the feeding rate for the overall nanofibril creating process and the yield of the nanofibrils in solution with various organic solvents were determined. Considering the influence of a change in the temperature on the status of the precipitated nanofibrils until feeding it into the spray nozzle, the margin of the surviving nanofibrils at a certain temperature was also investigated. To verify the superiority of our strategy and present directions regarding its application to industry, arrays of organic solar cells based on a 3D non-woven nanofabric structure consisting of P3HT nanofibrils were designed and fabricated using our in situ process combined with a spray-coating system. As a result, through the in situ cooling process, a considerable solar energy harvesting efficiency near 4%, which is a state-of-the-art value in a bi-layer-based solar cell, was obtained.
17 citations
TL;DR: A compartmentalized multidomain alignment state of a layer of liquid crystal display is achieved using an ultrathin, highly transparent, and ultrafast-responsive alignment layer fabricated by a simple method.
Abstract: A compartmentalized multidomain alignment state of a layer of liquid crystal display is achieved using an ultrathin, highly transparent, and ultrafast-responsive alignment layer fabricated by a simple method. The ultrathin alignment layer consists of a self-assembled oligomer layer of poly(dimethylsiloxane) (PDMS) formed by utilizing the oligomers that diffuse out from a PDMS elastomer stamp during a contact printing process.
10 citations
TL;DR: The role of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as an n-type homologue buffer layer (HBL) was investigated in a bulk-heterojunction solar cell as discussed by the authors.