Solution Processable Hybrid Hole Transport Layers for Organic Solar cells with Highly Enhanced Open-Circuit Voltage and Fill Factor

이형석,한용운,문두경 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Organic solar cells (OSCs) have been studied because of their low cost and simple manufacture process. However, OSCs have some disadvantages such as unbalanced carrier mobility, low stability resulted from energy level mismatch between electrode and active layer. To solve these issues, many researchers replaced MoO3 to various HTLs materials. Through solution process, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is commonly used as HTLs by its high conductivity and solution processable properties. However, devices introduced PEDOT:PSS still attain lower power conversion efficiency (PCE) and stability than MoO3 deposited devices. Solution processable hybrid HTLs can be modified properties of carrier mobility and energy levels. In this study, we fabricated inverted structured OSCs with hybrid HTLs via solution process. As a result, the stability and performance of OSCs with solution processable hybrid HTLs were enhanced.

최적화된 전자 수송층을 활용한 완전한 용액공정 기반 녹색 유기발광다이오드

한주원,김용현,Han, Joo Won,Kim, Yong Hyun 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.7

Solution-processed organic light-emitting diodes (OLEDs) have the advantages of low cost, fast fabrication, and large-area devices. However, most studies on solution-processed OLEDs have mainly focused on solution-processable hole transporting materials or emissive materials. Here, we report fully solution-processed green OLEDs including hole/electron transport layers and emissive layers. The electrical and optical properties of OLEDs based on solution-processed TPBi (2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) as the electron transport layer were investigated with respect to the spin speed and the number of layers. The performance of OLEDs with solution-processed TPBi exhibits a power efficiency of 9.4 lm/W. We believe that the solution-processed electron transport layers can contribute to the development of efficient fully solution-processed multilayered OLEDs.

Impact of Interface Mixing on the Performance of Solution Processed Organic Light Emitting DiodesImpedance and Ultraviolet Photoelectron Spectroscopy Study

Ahn, Dong A,Lee, Seungjun,Chung, Jaegwan,Park, Yongsup,Suh, Min Chul American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.27

<P>We investigated interfacial mixing of solution-processed organic light-emitting devices (OLEDs) using impedance spectroscopy (IS) and ultraviolet photoelectron spectroscopy (UPS) and its impact on device performance. We focused on interfacial mixing between a solution processed cross-linkable hole transport layer (XM) and an emitting layer (EML), formed either by solution processing or vacuum evaporation. The results of IS and UPS clearly indicated that extensive interfacial mixing was unavoidable, even after the XM was cross-linked to make it insoluble and rinsed to remove residual soluble species, if the subsequent EML was solution processed. In addition, we also demonstrated that interfacial mixing indeed increased hole current density in corresponding hole only device (HOD). In fact, the hole injection efficiency could be an order of magnitude better when the EML was solution processed rather than vacuum evaporated. We investigated such behavior to find the desirable process condition of solution-processed OLEDs.</P>

Effective Atmospheric-Pressure Plasma Treatment toward High-Performance Solution-Processed Oxide Thin-Film Transistors

Park, Jintaek,Huh, Jae-Eun,Lee, Sung-Eun,Lee, Junhee,Lee, Won Hyung,Lim, Keon-Hee,Kim, Youn Sang American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.36

<P>Solution-processed oxide semiconductors (OSs) have attracted much attention because they can simply, quickly, and cheaply produce transparent channels on flexible substrates. However, despite such advantages, in the fabrication process of OS thin-film transistors (TFTs) using the solution process, it is a fatal problem that there are hardly any ways to simply and effectively control important TFT parameters, including the turn-on voltage (<I>V</I><SUB>on</SUB>) and on/off current ratio. For the practical application of solution-processed OS TFT, approaches to simply and effectively control the parameters are urgently required. Here, we newly propose an atmospheric-pressure plasma (APP) treatment that can simply and effectively control the electrical properties in solution-processed InO<I><SUB>x</SUB></I> TFTs. Through exposure of APP, we successfully realized the changes in important TFT parameters of solution-processed InO<I><SUB>x</SUB></I> TFT, <I>V</I><SUB>on</SUB> from −11.4 to −1.9 V and the on/off current ratio from ∼10<SUP>3</SUP> to ∼10<SUP>6</SUP>, which still keep up the high field-effect mobility (>20 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>). On the basis of various analyses such as X-ray-based analysis and UV-visible spectroscopy, we identified that the APP treatment can effectively control oxygen vacancy and carrier concentration in solution-processed OS.</P> [FIG OMISSION]</BR>

Solution-processed lanthanum-doped Al₂O₃ gate dielectrics for high-mobility metal-oxide thin-film transistors

Kim, Jaeyoung,Choi, Seungbeom,Jo, Jeong-Wan,Park, Sung Kyu,Kim, Yong-Hoon Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>Solution-processed oxide gate dielectrics play an important in thin-film transistors (TFTs), determining their operation voltage, device performance and power consumption. Up to now, various solution-processed oxide gate dielectrics such as aluminum oxide (Al<SUB>2</SUB>O<SUB>3</SUB>) have been surveyed, however, they generally exhibit relatively high leakage current, low dielectric constant, and hysteresis which are unfavorable for stable device operation. Here, we demonstrate solution-processed lanthanum (La)-doped Al<SUB>2</SUB>O<SUB>3</SUB> (LAO) gate dielectrics which exhibit low leakage current density, high dielectric constant, and relatively small frequency-dependent capacitance variation. In order to find the optimal doping concentration of lanthanum in Al<SUB>2</SUB>O<SUB>3</SUB> film, various electrical, morphological, and spectroscopic analyses were carried out. We found that the addition of lanthanum in Al<SUB>2</SUB>O<SUB>3</SUB> film effectively reduced the defective metal hydroxide bonding states within the film and significantly enhanced its dielectric characteristics. At an optimal doping concentration of lanthanum (20 at.%), gate dielectrics showing leakage current density, dielectric constant, and breakdown field of ~10<SUP>−8</SUP> A/cm<SUP>2</SUP> (at 2 MV/cm), 10.5, and >5 MV/cm were obtained. Using the LAO film as a gate dielectric, solution-processed indium-zinc-oxide TFTs having a field-effect mobility of 11.9 cm<SUP>2</SUP>/V-s, subthreshold slope of 0.38 V/dec, and on/off ratio of 10<SUP>4</SUP>–10<SUP>5</SUP> were demonstrated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lanthanum-doped Al<SUB>2</SUB>O<SUB>3</SUB> gate dielectrics were fabricated by using a solution process. </LI> <LI> The lanthanum doping enhanced the dielectric properties of Al<SUB>2</SUB>O<SUB>3</SUB> films. </LI> <LI> Solution-processed indium-zinc-oxide thin-film transistors were demonstrated. </LI> </UL> </P>

Solution-processed high-k thin films as a resistive switching for ReRAM applications

Jang, K.H.,Oh, S.M.,An, H.M.,Cho, W.J. Elsevier 2014 Current Applied Physics Vol.14 No.3

Resistive switching characteristics of solution-processed high-k thin films (HfO<SUB>x</SUB> and TaO<SUB>x</SUB>) were investigated for ReRAM applications. The thickness of solution-processed high-k thin films can be easily controlled by simple spin coating. We optimized the critical thickness of solution-processed HfO<SUB>x</SUB> and TaO<SUB>x</SUB> thin films, for reliable ReRAM operations. A similar bipolar resistive switching behavior was observed from both solution-processed and sputter-processed HfO<SUB>x</SUB> films. Furthermore, it was found that the solution-processed HfO<SUB>x</SUB> and TaO<SUB>x</SUB> films have a uniform resistive switching characteristic. The dominant conduction of these solution-processed films is described by Ohmic conduction in the low-resistance state. On the other hand, Ohmic conduction at low voltage and Poole-Frenkel emission at high voltage dominate in the high-resistance state. It was verified that the solution-processed HfO<SUB>x</SUB> and TaO<SUB>x</SUB> films have superior endurance and retention characteristics. Therefore, ReRAM devices based on solution-processed high-k materials are expected to be a promising candidate, for usage of resistive memory in glass substrate or flexible substrate based electronic devices.

Image-processing technique to detect carbonation regions of concrete sprayed with a phenolphthalein solution

Choi, Jeong-Il,Lee, Yun,Kim, Yun Yong,Lee, Bang Yeon Elsevier BV 2017 Construction and Building Materials Vol.154 No.-

<P><B>Abstract</B></P> <P>The carbonation of concrete is one of the factors influencing the durability of reinforced concrete members or structures. Manual measurements can reportedly induce low reproducibility when measuring carbonation depths. This study presents a new image-processing algorithm for the automatic detection of carbonated regions of concrete sprayed with a phenolphthalein solution. The proposed image-processing algorithm consists of a primary detection process based on binarization and a morphology analysis and a secondary detection process based on a convex hull. A series of tests of images of carbonated concrete sprayed with the phenolphthalein solution is conducted to assess the validity of the proposed image-processing algorithm. The validation test results showed that the proposed image-processing algorithm is capable of the accurate detection of carbonated concrete regions compared to direct visual inspections.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Image-processing technique to detect carbonation regions of concrete is developed. </LI> <LI> The proposed algorithm consists of primary and secondary detection processes. </LI> <LI> The proposed algorithm is capable of the accurate detection of carbonated regions. </LI> </UL> </P>

Effects of Solution Temperature on Solution-Processed High-Performance Metal Oxide Thin-Film Transistors

Lee, Keun Ho,Park, Jee Ho,Yoo, Young Bum,Jang, Woo Soon,Oh, Jin Young,Chae, Soo Sang,Moon, Kyeong Ju,Myoung, Jae Min,Baik, Hong Koo American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.7

<P>Herein, we report a novel and easy strategy for fabricating solution-processed metal oxide thin-film transistors by controlling the dielectric constant of H<SUB>2</SUB>O 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 cm<SUP>2</SUP>/(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 cm<SUP>2</SUP>/(V s), respectively, after annealing at 350 °C. When the IZO precursor solution is at 4 °C, metal cations such as indium (In<SUP>3+</SUP>) and zinc ions (Zn<SUP>2+</SUP>) can be fully surrounded by H<SUB>2</SUB>O molecules, because of the higher dielectric constant of H<SUB>2</SUB>O at lower temperatures. These chemical complexes in the IZO precursor solution at 4 °C are advantageous for thermal hydrolysis and condensation reactions yielding a metal oxide lattice, because of their high potential energies. The IZO TFTs fabricated from the IZO precursor solution at 4 °C had the highest mobility because of the formation of many metal–oxygen–metal (M-O-M) bonds under these conditions. In these bonds, the ns-orbitals of the metal cations overlap each other and form electron conduction pathways. Thus, the formation of a high proportion of M-O-M bonds in the IZO thin films is advantageous for electron conduction, because oxide lattices allow electrons to travel easily through the IZO.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-7/am3032629/production/images/medium/am-2012-032629_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am3032629'>ACS Electronic Supporting Info</A></P>

Solution-processed high-k thin films as a resistive switching for ReRAM applications

장기현,오세만,안호명,조원주 한국물리학회 2014 Current Applied Physics Vol.14 No.3

Resistive switching characteristics of solution-processed high-k thin films (HfOx and TaOx) were investigated for ReRAM applications. The thickness of solution-processed high-k thin films can be easily controlled by simple spin coating. We optimized the critical thickness of solution-processed HfOx and TaOx thin films, for reliable ReRAM operations. A similar bipolar resistive switching behavior was observed from both solution-processed and sputter-processed HfOx films. Furthermore, it was found that the solution-processed HfOx and TaOx films have a uniform resistive switching characteristic. The dominant conduction of these solution-processed films is described by Ohmic conduction in the lowresistance state. On the other hand, Ohmic conduction at low voltage and PooleeFrenkel emission at high voltage dominate in the high-resistance state. It was verified that the solution-processed HfOx and TaOx films have superior endurance and retention characteristics. Therefore, ReRAM devices based on solution-processed high-k materials are expected to be a promising candidate, for usage of resistive memory in glass substrate or flexible substrate based electronic devices.

용액법으로 제작된 ZnSnO 박막트랜지스터의 전극 물질에 따른 계면 접촉특성 연구

정영민,송근규,우규희,전태환,정양호,문주호,Jeong, Young-Min,Song, Keun-Kyu,Woo, Kyoo-Hee,Jun, Tae-Hwan,Jung, Yang-Ho,Moon, Joo-Ho 한국재료학회 2010 한국재료학회지 Vol.20 No.8

We studied the influence of different types of metal electrodes on the performance of solution-processed zinc tin oxide (ZTO) thin-film transistors. The ZTO thin-film was obtained by spin-coating the sol-gel solution made from zinc acetate and tin acetate dissolved in 2-methoxyethanol. Various metals, Al, Au, Ag and Cu, were used to make contacts with the solution-deposited ZTO layers by selective deposition through a metal shadow mask. Contact resistance between the metal electrode and the semiconductor was obtained by a transmission line method (TLM). The device based on an Al electrode exhibited superior performance as compared to those based on other metals. Kelvin probe force microscopy (KPFM) allowed us to measure the work function of the oxide semiconductor to understand the variation of the device performance as a function of the types metal electrode. The solution-processed ZTO contained nanopores that resulted from the burnout of the organic species during the annealing. This different surface structure associated with the solution-processed ZTO gave a rise to a different work function value as compared to the vacuum-deposited counterpart. More oxygen could be adsorbed on the nanoporous solution-processed ZTO with large accessible surface areas, which increased its work function. This observation explained why the solution-processed ZTO makes an ohmic contact with the Al electrode.