Browsing by Author "Du, Jia"
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Item Biocompatible Organic Charge Transfer Complex Nanoparticles Based on a Semi-Crystalline Cellulose Template(Royal Society of Chemistry, 2015-06-19) Nagai, A.; Miller, J. B.; Du, Jia; Kos, P.; Stefan, Mihaela C.; Siegwart, D. J.; 55039821 (Stefan, MC); Stefan, Mihaela C.Using a bio-inspired cellulose template, new charge transfer (CT) nanoparticles (NPs) with unique and intriguing emission properties are reported. Pyrene-modified 2,3-di-O-methyl cellulose formed CT complexes with small molecule acceptors, e.g. 7,7,8,8-tetracyanoquinodimethane (TCNQ), and exhibited aggregation-induced emission (AIE) in aqueous medium upon nanoparticle formation. The TCNQ-CT NPs showed multicolor fluorescence emissions at 370-400 nm, 602 nm and 777 nm, when excited at 330 nm, 485 nm and 620 nm respectively. The cellulose-TCNQ NPs are biocompatible and demonstrate an advance in the use of the CT mechanism for biomedical imaging applications both in vitro and in vivo.Item Developments of Furan and Benzodifuran Semiconductors for Organic Photovoltaics(Royal Society of Chemistry, 2015-02-13) Huang, Peishen; Du, Jia; Biewer, Michael C.; Stefan, Mihaela C.; 55039821 (Stefan, MC); Biewer, Michael C.; Stefan, Mihaela C.This review describes the developments of organic photovoltaic materials containing furan or benzo[1,2-b:4,5-b']difuran (BDF) building blocks. Promising power conversion efficiencies above 6% have been achieved in the past two years for the BDF donor-acceptor polymers. Fundamentals of organic photovoltaics are briefly introduced at the beginning of this review. The uniqueness and advantages of BDF building block in semiconducting materials are discussed and compared with benzo[1,2-b:4,5-b']dithiophene analogues.Item Donor-Acceptor Organic Semiconductors: Investigations of Optical, Electronic, and Morphological Properties(2017-05) Du, Jia; Stefan, Mihaela C.Organic semiconductors have drawn remarkable attention due to their light weight, feasible fabrication and flexibility in the field of organic photovoltaics and field effect transistors. The rapidly increasing world population and the accompanied with huge energy demands are becoming a big concern for the future, which makes harvesting unlimited solar power using photovoltaic devices extremely important. A remarkable amount of research has been done to improve the power conversion efficiency in terms of the materials design, morphology investigations and device engineering. Organic field effect transistors utilizing solution-processed conjugated polymers can be fabricated efficiently at a low cost roll-to-roll technique over a large area. Designing high performing conjugated polymers and investigating their morphology is essential. In this dissertation, the fundamentals and the recent developments of organic semiconductors are covered in Chapter 1. The basic operation mechanism of organic photovoltaics and field effect transistors are introduced. Semiconducting molecules and polymers that have been reported using benzo[1,2-b;4,5-b’]dithiophene (BDT), benzo[1,2-b;4,5-b’]difuran (BDF), 2,1,3-benzothiadiazole (BT), and diketopyrrolopyrrole (DPP), are discussed and summarized. Chapter 2 describes the isomeric effect of two small molecules containing BDT and BT units on the photovoltaic performance. The influence on UV-vis absorption, frontier molecular orbital energy level, and morphology due to the position of the BT unit was systematically investigated. The photovoltaic performance was studied in bulk heterojunction solar cells with [6, 6]-phenyl-C71-butyric acid methyl ester used as the acceptor. Chapter 3 describes the synthesis of novel conjugated polymers built from BDF and furan substituted DPP unit. Furan and its derivatives are regarded as green and renewable building units. This polymer was tested in bulk heterojunction solar cells with the highest power conversion efficiency of 5.55% and high fill factor of 0.73 achieved when 4% diphenyl ether was applied to optimize the phase separation. The morphology of the blend films was investigated by atomic force microscopy, grazing incident wide-angle X-ray scattering and transmission electron microscopy. In Chapter 4, an alternative copolymer built from furan substituted DPP and (E)-1,2-di(furan-2-yl)ethene was synthesized by Stille coupling and employed in organic field effect transistors. Hole mobility of 0.42 cm2 V-1 s-1 was achieved with current on/off ratio of 104 after annealing the thin film at 150 oC for 5 minutes. The higher mobility after thermal annealing was explained by the increased crystallinity, which was revealed by atomic force microscopy and grazing incident X-ray diffraction. At the end, the prospective and future work for the organic photovoltaics and field effect transistors are discussed in Chapter 5.Item A Semiconducting Liquid Crystalline Block Copolymer Containing Regioregular Poly-(3-hexylthiophene) and Nematic Poly(n-hexyl Isocyanate) and its Application in Bulk Heterojunction Solar Cells(Royal Soc Chemistry, 2014-08-06) Bhatt, Mahesh P.; Du, Jia; Rainbolt, Elizabeth A.; Pathiranage, Taniya M. S. K.; Huang, Peishen; Reuther, James F.; Novak, Bruce M.; Biewer, Michael C.; Stefan, Mihaela C.; 0000 0000 8413 1147 (Novak, BM); 98037603 (Novak, BM); 55039821 (Stefan, MC); Novak, Bruce M.; Biewer, Michael C.; Stefan, Mihaela C.A liquid crystalline diblock copolymer containing regioregular poly(3-hexylthiophene) (P3HT) and poly-(n-hexyl isocyanate) (PHIC) was synthesized by the combination of Grignard metathesis polymerization (GRIM) and titanium mediated coordination polymerization methods. The poly(3-hexylthiophene)-b-poly(n-hexyl isocyanate) (P3HT-b-PHIC) diblock copolymer used in this study contained ~10 mol% of P3HT and ~90 mol% of PHIC. The diblock copolymer displayed solvatochromism in THF-water and THF-methanol mixtures. The field-effect mobilities of the synthesized block copolymer were measured in bottom gate-bottom contact organic field-effect transistors (OFETs). The surface morphology of the polymer thin film was investigated in the channel region of the OFET devices by tapping mode atomic force microscopy (TMAFM). The diblock copolymer displayed nanostructured morphology in thin film and had good mobility despite the low content of the semiconducting P3HT block. The diblock copolymer was also used as an additive to improve the performance of P3HT/PCBM bulk heterojunction (BHJ) solar cells. Liquid crystalline characteristics of the diblock copolymer were examined by cross-polarizing microscopy and X-ray diffraction.Item Structural Variation of Donor-Acceptor Copolymers Containing Benzodithiophene with Bithienyl Substituents to Achieve High Open Circuit Voltage in Bulk Heterojunction Solar Cells(Royal Soc Chemistry, 2013-11-06) Kularatne, Ruvini S.; Taenzler, Ferdinand J.; Magurudeniya, Harsha D.; Du, Jia; Murphy, John W.; Sheina, E. E.; Gnade, Bruce E.; Biewer, Michael C.; Stefan, Mihaela C.; 0000 0003 8371 1336 (Gnade, BE); 00049719 (Gnade, BE); 55039821 (Stefan, MC); Gnade, Bruce E.; Biewer, Michael C.; Stefan, Mihaela C.Three new donor-acceptor copolymers P1, P2, and P3 were synthesized with benzodithiophene with bithienyl substituents as the donor and 5,6-difluorobenzo[c][1,2,5]thiadiazole, 4,7-di(thiophen-2-yl)benzo[c][1,2,5] thiadiazole, and 5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole as the acceptors, respectively. The insertion of thiophene spacer between the donor and the acceptor broadened the absorption of the polymers P2 and P3 and resulted in a red shift of ~30 nm as compared to that of the polymer P1. However, the inclusion of fluorine atoms on the polymer had detrimental effects on the photovoltaic properties of the polymers. The synthesized donor-acceptor polymers were tested in bulk heterojunction (BHJ) solar cells with [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) acceptor. Polymer P2 gave a PCE of 3.52% with PC71BM in which the active layer was prepared in chloroform with 3% v/v 1,8-diiodooctane (DIO) additive. The effect of fluorine substitution and thiophene group insertion on the UV/Vis absorbance, photovoltaic performances, morphology, and charge carrier mobilities for the polymers are discussed.