Microstructural Control over Soluble Pentacene Deposited by Capillary Pen Printing for Organic Electronics

Lee, Wi Hyoung,Min, Honggi,Park, Namwoo,Lee, Junghwi,Seo, Eunsuk,Kang, Boseok,Cho, Kilwon,Lee, Hwa Sung American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.16

<P>Research into printing techniques has received special attention for the commercialization of cost-efficient organic electronics. Here, we have developed a capillary pen printing technique to realize a large-area pattern array of organic transistors and systematically investigated self-organization behavior of printed soluble organic semiconductor ink. The capillary pen-printed deposits of organic semiconductor, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS_PEN), was well-optimized in terms of morphological and microstructural properties by using ink with mixed solvents of chlorobenzene (CB) and 1,2-dichlorobenzene (DCB). Especially, a 1:1 solvent ratio results in the best transistor performances. This result is attributed to the unique evaporation characteristics of the TIPS_PEN deposits where fast evaporation of CB induces a morphological evolution at the initial printed position, and the remaining DCB with slow evaporation rate offers a favorable crystal evolution at the pinned position. Finally, a large-area transistor array was facilely fabricated by drawing organic electrodes and active layers with a versatile capillary pen. Our approach provides an efficient printing technique for fabricating large-area arrays of organic electronics and further suggests a methodology to enhance their performances by microstructural control of the printed organic semiconducting deposits.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-16/am401698c/production/images/medium/am-2013-01698c_0010.gif'></P>

Efficiency and Lifetime Improvement of Organic Light- Emitting Diodes with a Use of Lithium-Carbonate- Incorportated Cathode Structure

Mok, Rang-Kyun,Kim, Tae-Wan The Korean Institute of Electrical and Electronic 2012 Transactions on Electrical and Electronic Material Vol.13 No.2

Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate ($Li_2CO_3$) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/$Alq_3$ (60 nm)/$Li_2CO_3$ (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of $Li_2CO_3$ layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of $Li_2CO_3$ layer is 0.7 nm, the current efficiency and luminance of the device at 8.0 V are improved by a factor of about 18 and 3,000 compared to the ones without the $Li_2CO_3$ layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of $Li_2CO_3$ electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of $Li_2CO_3$ layer, the optimum thickness of $Li_2CO_3$ layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by $Li_2CO_3$ layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of $Li_2CO_3$ layer to be about 1.0 nm.

Toward High-performance Quinoxaline Based Unfused Non-fullerene Acceptors for Organic Solar Cells

Amna Ayub,Muhammad Ans,Sehrish Gul,Ahmed M. Shawky,Khurshid Ayub,Javed Iqbal,Muhammad Ali Hashmi,Ahmed Lakhani 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.1

Unfused non-fullerene acceptors with the advantages of simple synthesis, high yields, and low cost have received a lot ofinterest in recent years. Herein, we designed fi ve structures (UF-M1–UF-M5) with unfused non-fullerene acceptors coupledto electron-defi cient quinoxaline (Qx) as the core unit via electron-donating cyclo-penta-dithiophene (CPDT) as the conjugatedbackbone by modifi cation in UF-Qx-2Cl taken as reference. Among all, mPW1PW91 method predicted λ max closestto the λ max of UF-Qx-2Cl, so we implemented the mPW1PW91 method with a 6-31G(d,p) basis set for the optimization ofdesigned geometries and their molecular electrostatic mapping (MEP). Further parameters like FMOs (frontier molecularorbitals), TDM (transition density matrix analysis), DOS (density of state analysis), electron–hole mobility rate (reorganizationenergies), dipole moment, and chemical quantum descriptive parameters were evaluated for organic photovoltaics. Among all, UF-M4 predicted better absorption in the gaseous and solvent phase (λ max = 726 nm and 789 nm respectively),lower bandgap (E g = 2.03 eV), higher dipole moment (1.99 and 5.33 debye in gaseous and solvent phase respectively), betterquantum chemical descriptive parameters, and higher electron mobility rate (λ e = 0.00766 eV). The results reveal that theacceptor molecule UF-M4 that has been created performs better in studies and better opportunities for organic-photovoltaics. To summarize, the unfused non-fullerene-based acceptor modifi cation technique has shown eff ective in paving the way forthe development of promising photovoltaic materials. All currently projected acceptor contributors (UF-M1–UF-M5) shouldbe targeted to produce future competent organic photovoltaics.

Organic/metal hybrid cathode for transparent organic light-emitting diodes

Huh, J.W.,Moon, J.,Lee, J.W.,Lee, J.,Cho, D.H.,Shin, J.W.,Han, J.H.,Hwang, J.,Joo, C.W.,Lee, J.I.,Chu, H.Y. Elsevier Science 2013 Organic electronics Vol.14 No.8

We report a highly transparent organic/metal hybrid cathode of a Cs-doped electron transport layer (Cs-ETL)/Ag for transparent organic light-emitting diode (TOLED) applications. Particular attention is paid to the surface morphology on the Ag film and its influence on the optical transparency and electrical conductivity. With the use of Cs-ETL, a smooth and continuous surface morphology of Ag film was achieved, leading to a high transmittance of ~75% in TOLED with a low sheet resistance of 4.5Ω/Sq in cathode film. We successfully applied our Cs-ETL/Ag transparent cathode to fabricate highly transparent OLEDs. Our approach suggests a new electrode structure for transparent OLED applications.

Enhanced photovoltaic performance in inverted organic photovoltaics using organic-inorganic hybrid electron transport layer

이의진,한용운,한재필,문두경 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

In this study, We modified ZnO electron transport layer (ETL) with water/alcohol soluble polymer and controlled the surface property of the organic-inorganic hybrid ETL (m-ZnO). The morphology of photoactive layer and interfacial contact between ETL and photoactive layer were enhanced by introducing m-ZnO. We fabricated inverted organic photovoltaic (IOPV) devices by introducing m-ZnO. For the reference device (ITO/ZnO/photoactive layer/MoO₃/Ag), the open circuit voltage (Voc), short circuit current (Jsc), fill factor (FF) and power conversion efficiency (PCE) were 0.717 V, 16.3 mA/cm², 64.7% and 7.2%, respect respectively. By introducing m-ZnO, the IOPV with ITO/m-ZnO/photoactive layer/MoO3/Ag, exhibited enhanced performances which were 0.737 V, 18.5 mA/cm², 65.7% and 9.0%.

Oxidation inhibition of poly(3-hexylthiophene-2,5-diyl) in the bulk heterojunction by an electron acceptor

Woo, Tae Gyun,Cha, Byeong Jun,Seo, Hyun Ook,Kim, Young Dok Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.458 No.-

<P><B>Abstract</B></P> <P>Poly(3-hexylthiophene-2,5-diyl) (P3HT) is an organic semiconducting polymer that is widely used in organic electronic devices such as organic solar cells. In this work, we studied the oxidation behavior of P3HT on glass under exposure to visible light and dry air. We also compared the oxidation behavior of bare P3HT films with that of P3HT/phenyl-C<SUB>61</SUB>-butyric acid methyl ester (PCBM) bulk heterojunction systems consisting of donor and acceptor. UV–Vis absorption spectroscopy and X-ray photoelectron spectroscopy were employed to provide evidence that optically excited P3HT could undergo oxidation, which was likely initiated via electron transfer from the conduction band of P3HT to O<SUB>2</SUB>, forming strongly oxidizing O<SUB>2</SUB> <SUP>–</SUP> species. By contrast, P3HT + PCBM yielded almost no oxidation of organic materials under the same conditions. PCBM was thus suggested to extract optically excited electrons from P3HT, thereby inhibiting the formation of O<SUB>2</SUB> <SUP>–</SUP>. PCBM thus played a role in separating electron-hole pairs from the photoactive layers of organic solar cells and affected the passivating oxidation of photoactive conjugate polymers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> P3HT, a semiconductive polymer, is easily oxidized by visible light under air. </LI> <LI> Oxidizing agent of P3HT is O<SUB>2</SUB> <SUP>–</SUP> formed by electron transfer from P3HT to O<SUB>2</SUB>. </LI> <LI> PC<SUB>61</SUB>BM, an electron acceptor, passivates oxidation of P3HT. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Exploring the ultrasonic nozzle spray-coating technique for the fabrication of solution-processed organic electronics

Han, Singu,Jeong, Heejeong,Jang, Hayeong,Baek, Seolhee,Kim, Se Hyun,Lee, Hwa Sung ELSEVIER 2017 ORGANIC ELECTRONICS Vol.49 No.-

<P><B>Abstract</B></P> <P>The ultrasonic nozzle (US) spray method was investigated for its utility in fabricating organic electrodes composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a standard conductive polymer material used to produce large-area low-cost OFETs. The US spray technique involves generating a solution spray by first passing the solution through a head and nozzle subjected to ultrasonic vibrations that induce atomization. This method is advantageous in that the resulting spray comprises extremely small solution droplets a few micrometers in diameter, unlike the spray produced using conventional air spray methods. The PEDOT:PSS US solution spraying process was optimized by controlling the flow rate of the N<SUB>2</SUB> carrier gas and the substrate temperature while monitoring the quality of the resulting PEDOT:PSS electrode films. The pentacene field-effect transistors prepared using the US spray method displayed a maximum field-effect mobility of 0.47 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP> (with an average value of 0.31 cm<SUP>2</SUP>V<SUP>−1</SUP>s<SUP>−1</SUP>), 35% better than the mobilities achieved using the conventional air spray method. In addition, the device-to-device reproducibility was improved, as indicated by a decrease in the standard deviation of the mobility values from 30% for the air spray devices to 24% for the US spray devices. These results indicated that the US spray technique is efficient and superior to the conventional air spray method for the development of low-cost large-area organic electronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> US spray method is investigated for printing organic PEDOT:PSS electrodes. </LI> <LI> Pentacene-FETs using US spray display 35% higher μ<SUB>FET</SUB> compared with conventional spray method. </LI> <LI> The mobility reproducibility is improved by a decrease of the standard deviation from 30% to 24%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Vapor-phase deposition of organic/inorganic hybrid layers and their applications

임성갑 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Organic-inorganic hybrid dielectrics have attracted considerable attention for improving both the dielectric constant (k) and mechanical flexibility of the gate dielectric layer for emerging flexible and wearable electronics. However, conventional solution-based hybrid materials, such as nanocomposite and self-assembled nanodielectrics, have limitations in the dielectric quality when the thickness is deep-scaled, which is critical to realizing high-performance flexible devices. This study proposes a novel vapor-phase synthesis method to form an ultrathin, homogeneous, high-k organic-inorganic hybrid dielectric. A series of hybrid dielectrics is synthesized via initiated chemical vapor deposition (iCVD) in a one-step manner. The hybrid dielectric synthesized via the iCVD process is a promising candidate for highperformance, low-power flexible electronics

Three‐Dimensional Integration of Organic Resistive Memory Devices

Song, Sunghoon,Cho, Byungjin,Kim, Tae‐,Wook,Ji, Yongsung,Jo, Minseok,Wang, Gunuk,Choe, Minhyeok,Kahng, Yung Ho,Hwang, Hyunsang,Lee, Takhee WILEY‐VCH Verlag 2010 Advanced Materials Vol.22 No.44

<P><B>Organic memory</B>: Our three‐dimensionally (3D) stacked 8 × 8 cross‐bar array organic resistive memory devices showed non‐volatile memory switching behavior, in which individual memory cells in the different layers can be independently controlled and monitored. The 3D stackable organic memory devices will enable achieving highly integrable organic memory devices and other organic‐based electronics with much increased cell density. </P>

Efficiency and Lifetime Improvement of Organic Light- Emitting Diodes with a Use of Lithium-Carbonate- Incorportated Cathode Structure

Rang Kyun Mok,김태완 한국전기전자재료학회 2012 Transactions on Electrical and Electronic Material Vol.13 No.2

Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate (Li2CO3) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/Alq3 (60 nm)/Li2CO3 (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of Li2CO3layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of Li2CO3 layer is 0.7 nm, the current efficiency and luminance of the device at 8.0V are improved by a factor of about 18 and 3,000 compared to the ones without the Li2CO3 layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of Li2CO3 electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of Li2CO3 layer, the optimum thickness of Li2CO3 layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by Li2CO3 layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of Li2CO3 layer to be about 1.0 nm.