Development of Organic Semiconductors for Soft Electronics

Organic semiconductors, Soft electronics, Colloid, Mini-emulsion synthesis, Breath-figure moldingOrganic semiconductor based soft electronic devices are demonstrated: (1) effects of conjugation length on charge transport in polymer semiconductors, (2) water-borne colloids of organic semiconductors, and (3) breath-figure molding of polymer semiconductors for sensors. To improve the charge carrier mobility of diketopyrrolopyrrole donor-acceptor copolymer semiconductors, the length of the donor building block is controlled using vinylene moieties, and its effects on crystalline structure and charge transport are systematically studied. We synthesize P29-DPP-TBT with two vinylene linkages between thiophene units and compare it with P29-DPP-TVT with single vinylene linkage. Density functional theory calculations predict enhanced backbone planarity of P29-DPP-TBT compared to P29-DPP-TVT, which can be related with the increased conjugation length of P29-DPP-TBT as proved by the increased free exciton bandwidth extracted from UV-vis absorption spectra and the wavenumber shift of the C–C peaks to higher values in Raman spectra. From two-dimensional grazing incident X-ray diffraction studies, it is turned out that the paracrystalline disorder is lower in P29-DPP-TBT than in P29-DPP-TVT. Near-edge X-ray absorption fine structure spectroscopy reveal that more edge-on structure of polymer backbone is formed in the case of P29-DPP-TBT. By measuring the temperature-dependence of the charge carrier mobilities, it is turned out that the activation energy for charge hopping is lower for P29-DPP-TBT than for P29-DPP-TVT. Collectively, these results imply that the substitution of extended π-conjugated donor moiety of polymeric semiconductors can yield a more planar backbone structure and thus enhanced intermolecular interaction which enables more perfect crystalline structure as well as enhanced charge transport behavior. A synthetic approach has demonstrated to enhance coalescence phenomenon during solidification of water-borne colloids so that thin, even, and continuous film morphology of polymer semiconductors can be realized. From theoretical study of complex colloids, it is shown that small-sized and uniform colloid particles are essential to minimize depletion contact energy between colloid particles and thus to enhance coalescence. Therefore, the newly synthesized polymer semiconductor is designed for better molecular affinity with surfactants, so that phase transfer of polymer semiconductors from organic phase to water phase can proceed more efficiently during mini-emulsion synthesis. This is achieved by substituting a Si atom to the branching C atom of the alkyl solubilizing group of a conventional donor-acceptor polymer semiconductor. Such a chemical modification increases the volumetric portion of hydrophobic alkyl chains and thus enables higher solu-bility as well as higher hydrophobicity, all of which are closely related with enhancing molecular affinity be-tween polymer semiconductor and surfactants. As a result, the performance of organic field-effect transistors fabricated from water-borne colloids can be improved to a level similar to the case of organic solvents. More importantly, the reproducibility of transistor performance is also greatly improved due to the small and uni-form water-borne colloidal particles. Strategically designed polymer semiconductor thin film morphology with both high responsivity to the specific gas analyte and high signal transport efficiency is reported to realize high-performance flexible NOx gas sensors. Breath-Figure (BF) molding of polymer semiconductors enables a finely defined degree of nano-porosity in polymer films with high reproducibility while maintaining a high charge carrier mobility characteristics of organic field effect transistors (OFETs). The optimized BF-OFET with a donor-acceptor copolymer exhibits a maximum responsivity of over 104%, sensitivity of 774%/ppm, and limit of detection (LOD) of 110 ppb against NO. When tested across at NO concentrations of 0.2–10 ppm, the BF-OFET gas sensor ex-hibits a response time of 100–300 s, which is suitable for safety purposes in practical applications. Further-more, BF-OFETs show a high reproducibility as confirmed by statistical analysis on 64 independently fabri-cated devices. Selectivity to NOx analytes is tested by comparing the sensing ability of BF-OFET to other re-ducing gases and volatile organic compounds. Finally, flexible BF-OFETs conjugated with plastic substrates are demonstrated and they exhibit a sensitivity of 500%/ppm and LOD of 215 ppb, with a responsivity degradation of only 14.2% after 10,000 bending cycle at 1% strain.YPart Ⅰ. Effects of conjugation length on crystalline perfectness and charge transport in diketopyrrolopyrrole-based polymer semiconductors 1 Ⅰ. Introduction 2 Ⅱ. Experimental Section 3 2.1 Materials 3 2.2 Device fabrication 3 2.3 Characterization 4 2.4 Measurements 4 Ⅲ. Results and Discussions 5 Ⅳ. Conclusion 13 Ⅴ. References 14 Part Ⅱ. Facilitating Phase Transfer of Polymer Semiconductor in Mini-Emulsion Synthesis via Molecular Affinity Engineering 18 Ⅰ. Introduction 19 Ⅱ. Experimental Section 21 2.1 Materials 21 2.2 Colloid synthesis 21 2.3 Device fabrication 21 2.4 Characterization 21 2.5 Measurements 22 Ⅲ. Results and Discussions 22 3.1 Efficiency of Mini-emulsion 22 3.2 Film Morphology 26 3.3 Crystallinity and Molecular Orientation 28 3.3 Electrical Properties of Organic Field-effect Transistors (OFETs) 30 Ⅳ. Conclusion 32 Ⅴ. References 33 Part Ⅲ. Breath-Figure Molding of Polymer Transistors to Implement Flexible and High-Performance NOx Sensors 36 Ⅰ. Introduction 37 Ⅱ. Experimental Section 39 2.1 Device fabrication 39 2.2 Film characterization 39 2.3 Measurements 40 Ⅲ. Results and Discussions 40 Ⅳ. Conclusion 50 Ⅴ. References 51 국문요약 55본 논문은 유기 반도체를 이용한 유연 소자 개발 방법들을 제시한다: (1) 고분자 반도체의 공액 길이에 따른 전하 이동 영향, (2) 수분산 유기 반도체 콜로이드 합성 및 이를 이용한 소자 개발, (3) breath-figure 패턴 몰딩법을 이용한 센서 개발. 디케토피롤로피롤(diketopyrrolopyrrole) 전자 주개-받개 구조의 공중합체 반도체의 전하 운반체 이동성을 향상시키기 위해, 주개 구조의 길이는 비닐렌 단위체를 사용하여 제어된 채 결정 구조 및 전하 수송에 미치는 영향을 체계적으로 연구한다. 티오펜 단위체 사이에 2 개의 비닐렌 결합을 갖는 P29-DPP-TBT를 합성하고 단일 비닐렌 결합을 갖는 P29-DPP-TVT와 비교한다. 분자 이론 계산을 통하여 P29-DPP-TVT와 비교하여 P29-DPP-TBT의 향상된 백본 평면성을 예측하고, 자외선-가시광선 흡광 스펙트럼과 라만 스펙트럼을 이용하여 추출된 자유 엑시톤 대역폭이 증가함에 따라 P29-DPP-TBT의 공액 길이가 길어짐을 증명한다. 2 차원 X- 선 회절 분석법을 이용하여, P29-DPP-TVT보다 P29-DPP-TBT에서 결정성이 뛰어남을 확인하였다. 추가적으로, X- 선 흡수 미세 구조 분광법에서 P29-DPP-TBT의 경우에 고분자 백본이 더 많은 에지-온 구조로 형성됨을 보여준다. 전하이동도의 온도 의존성을 측정함으로써, 전하 호핑을 위한 활성화 에너지는 P29-DPP-TVT보다 P29-DPP-TBT에 대해 더 낮은 것으로 밝혀졌다. 종합적으로, 이들 결과는 공중합체 고분자 반도체의 연장된 π- 공액 전자 주개 부분의 치환이 보다 평면적 인 골격 구조를 생성할 수 있고, 이에 따라 보다 완전한 결정질 구조 및 향상된 전하 수송 거동을 가능하게 하여 분자간 상호 작용을 향상시킬 수 있음을 의미한다. 고분자 합성 측면에 있어 수성 콜로이드의 박막화 동안 응축 현상을 향상시켜서, 고분자 반도체의 얇고 균일하며 연속적인 박막 형태가 실현될 수 있음을 입증하였다. 콜로이드에 대한 이론적 연구로, 크기가 작고 균일한 콜로이드 입자가 콜로이드 입자 사이의 공핍 접촉 에너지를 최소화하고 따라서 응축을 향상시키는 데 필수적이라는 것이 밝혀졌다. 따라서, 새롭게 합성된 공중합체 고분자 반도체는 계면활성제와의 분자 친화성이 향상되도록 설계되어, 유기상으로부터 수상으로 공중합체 고분자 반도체의 상 전이가 미니-에멀젼 합성 동안 보다 효율적으로 진행될 수 있다. 이는 통상적인 전자 주개-받개 구조의 공중합체 고분자 반도체의 알킬 체인 그룹의 분 지형 C 원자에 Si 원자를 치환함으로써 가능하게 하였다. 이러한 화학적 변형은 소수성 알킬 체인의 부피를 증가시키고 따라서 더 높은 용해도 및 더 높은 소수성을 가능하게 하며, 이는 모두 공중합체 고분자 반도체와 계면활성제 사이의 분자 친화도를 향상시키는 것과 밀접한 관련이 있다. 결과적으로, 수계 콜로이드로 제조된 유기 전계 효과 트랜지스터의 성능은 유기 용매의 경우와 유사한 수준으로 개선될 수 있음을 입증하였다. 더불어 작고 균일한 수성 콜로이드 입자로 인해 박막 트랜지스터 성능의 재현성이 크게 향상된다. 특정 가스 분석 물질에 대한 높은 반응성과 높은 신호 전송 효율을 모두 갖춘 고분자 반도체 박막 모폴로지를 구현함으로써, 고성능의 유연한 NOx 가스 센서를 실현하였다. 고분자 반도체의 Breath-Figure (BF) 몰딩은 유기 전계 효과 트랜지스터 (OFET)의 높은 전하 캐리어 이동 특성을 유지하면서 고분자 박막에서 미세한 크기의 나노 다공성 표면 개질을 가능하게 하였다. 전자 주개-받개 구조의 공중합체 기반의 최적화된 BF-OFET는 최대 104 % 이상의 반응성과, 774% / ppm의 감도 및 NO에 대한 110 ppb의 검출 한계 (LOD)를 나타낸다. 0.2 ~ 10ppm의 NO 농도에서 측정시에 BF-OFET 가스 센서는 100 ~ 300 초의 응답 시간을 나타내며 이는 실제 응용 소자로 쓰일 수 있는 수준이다. 또한, BF-OFET는 64 개의 독립적으로 제조된 소자에 대한 통계 분석에 의해 확인 된 바와 같이 높은 재현성을 나타낸다. NOx 가스에 대한 선택성은 BF-OFET의 감지 능력을 다른 환원 가스 및 휘발성 유기 화합물과 비교하여 측정하였다. 최종적으로 플라스틱 기판과 접합된 유연한 BF-OFET을 구현하였으며 이 소자는 1% 변형률에서 10,000 회 굽힘 주기 후 14.2%의 응답성 저하를 보였으며, 500 % / ppm의 감도와 215ppb의 LOD를 나타냈다.MasterdCollectio

Measuring Interactions among Agricultural Productivity, Trade Openness, Agricultural GDP, and Income in Korea (1972- 2007)

Agricultural and Food Policy,

"Choice of Air Cargo Transshipment Airport: An Application to Air Cargo Traffic to/from Northeast Asia"

Based on a unique data set of 760 air cargo transshipment routings to/from the Northeast Asian region in 2000, this paper applies an aggregate form of multinomial logit model to identify the critical factors influencing air cargo transshipment route choice decisions. The analysis focuses on the trade-off between monetary cost and time cost while considering other variables relevant for choice of transshipment airport. The estimation method considers the presence of unobserved attributes, and corrects for resulting endogeneity via a two-stage least squares estimation using instrumental variables. Our empirical results show that choice of air cargo transshipment hub is more sensitive to time cost than the monetary costs such as landing fees and line-haul price. For example, our simulation results suggest that a one-hour reduction in total transport and processing time for a particular O-D air cargo traffic would be more effective than a US$1,000 reduction in airport charges. This suggests that it is important to reduce air cargo connecting time at an airport via adequate investment in capacity and automation even by increasing landing and other airport charges.

Theory of magnetic field-induced metaelectric critical end point in BiMn2_2O5_5

A recent experiment on the multiferroic BiMn$_2$O$_5$ compound under a strong applied magnetic field revealed a rich phase diagram driven by the coupling of magnetic and charge (dipolar) degrees of freedom. Based on the exchange-striction mechanism, we propose here a theoretical model with the intent to capture the interplay of the spin and dipolar moments in the presence of a magnetic field in BiMn$_2$O$_5$. Experimentally observed behavior of the dielectric constants, magnetic susceptibility, and the polarization is, for the most part, reproduced by our model. The critical behavior observed near the polarization reversal $(P=0)$ point in the phase diagram is interpreted as arising from the proximity to the critical end point.Comment: Theory; relevant experiment uploaded as arXiv:0810.190

Physical properties of transparent perovskite oxides (Ba,La)SnO3 with high electrical mobility at room temperature

Transparent electronic materials are increasingly in demand for a variety of optoelectronic applications. BaSnO3 is a semiconducting oxide with a large band gap of more than 3.1 eV. Recently, we discovered that La doped BaSnO3 exhibits unusually high electrical mobility of 320 cm^2(Vs)^-1 at room temperature and superior thermal stability at high temperatures [H. J. Kim et al. Appl. Phys. Express. 5, 061102 (2012)]. Following that work, we report various physical properties of (Ba,La)SnO3 single crystals and films including temperature-dependent transport and phonon properties, optical properties and first-principles calculations. We find that almost doping-independent mobility of 200-300 cm^2(Vs)^-1 is realized in the single crystals in a broad doping range from 1.0x10^19 to 4.0x10^20 cm^-3. Moreover, the conductivity of ~10^4 ohm^-1cm^-1 reached at the latter carrier density is comparable to the highest value. We attribute the high mobility to several physical properties of (Ba,La)SnO3: a small effective mass coming from the ideal Sn-O-Sn bonding, small disorder effects due to the doping away from the SnO2 conduction channel, and reduced carrier scattering due to the high dielectric constant. The observation of a reduced mobility of ~70 cm^2(Vs)^-1 in the film is mainly attributed to additional carrier-scatterings which are presumably created by the lattice mismatch between the substrate SrTiO3 and (Ba,La)SnO3. The main optical gap of (Ba,La)SnO3 single crystals remained at about 3.33 eV and the in-gap states only slightly increased, thus maintaining optical transparency in the visible region. Based on these, we suggest that the doped BaSnO3 system holds great potential for realizing all perovskite-based, transparent high-frequency high-power functional devices as well as highly mobile two-dimensional electron gas via interface control of heterostructured films.Comment: 31 pages, 7 figure

Processing SPARQL queries with regular expressions in RDF databases

Background: As the Resource Description Framework (RDF) data model is widely used for modeling and sharing a lot of online bioinformatics resources such as Uniprot (dev.isb-sib.ch/projects/uniprot-rdf) or Bio2RDF (bio2rdf.org), SPARQL - a W3C recommendation query for RDF databases - has become an important query language for querying the bioinformatics knowledge bases. Moreover, due to the diversity of users' requests for extracting information from the RDF data as well as the lack of users' knowledge about the exact value of each fact in the RDF databases, it is desirable to use the SPARQL query with regular expression patterns for querying the RDF data. To the best of our knowledge, there is currently no work that efficiently supports regular expression processing in SPARQL over RDF databases. Most of the existing techniques for processing regular expressions are designed for querying a text corpus, or only for supporting the matching over the paths in an RDF graph. Results: In this paper, we propose a novel framework for supporting regular expression processing in SPARQL query. Our contributions can be summarized as follows. 1) We propose an efficient framework for processing SPARQL queries with regular expression patterns in RDF databases. 2) We propose a cost model in order to adapt the proposed framework in the existing query optimizers. 3) We build a prototype for the proposed framework in C++ and conduct extensive experiments demonstrating the efficiency and effectiveness of our technique. Conclusions: Experiments with a full-blown RDF engine show that our framework outperforms the existing ones by up to two orders of magnitude in processing SPARQL queries with regular expression patterns.X113sciescopu