Photochemical Sciences Ph.D. Dissertations

Stable Hetero-Acene Analogs of Heptacene: The Synthesis and Study of their Conductive Properties in Organic Transistors And The Photo-induced Formation of Quantum Dot – Conductive Polymers (QD:CP) for Application in Photovoltaics

Date of Award

2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Douglas Neckers

Second Advisor

Thomas Kinstle (Committee Member)

Third Advisor

Marshall Wilson (Committee Member)

Fourth Advisor

Andreas Luescher (Committee Member)

Abstract

Part I: Stable Hetero-Acene Analogs of Heptacene: The Synthesis and Study of their Conductive Properties in Organic Transistors. The surge of organic electronics in the last two decades has augmented the necessity for the development of high performance devices with superior and less expensive processability. Polycyclic Aromatic Hydrocarbons (PAHs) have been widely investigated for this purpose2-5. With advancement in this field, PAH-based organic semiconductors, in some instances, have superseded Si in performance6-7. They exhibit hole mobilities as high8 as 5.5 cm2V-1S-1. Pentacene, for example, has become a benchmark for organic molecular semiconductors8. Use of such materials for fabrication of electronic devices, however, is limited due to their extreme lack of stability under ambient conditions. Therefore, efforts have been made to develop materials that exhibit comparable mobilities, and also are air-stable. Heterocyclic aromatic hydrocarbons were first developed as viable materials in this. However, though they are quite stable under ambient conditions, their low hole mobilities as compared to their PAH counterparts are an issue. Recently, heterocyclic aromatic hydrocarbons with high air-stable mobilities have been reported. Dinaptho[2,3-b:2,3-f]thieno[3,2-b]-thiophene (DNTT)9-11, for example, showed mobilities as high as 3.1 cm2V-1S-1. It is believed that materials with additional fused rings fused in such systems will allow higher stacking and better molecular packing, leading to higher mobilities. Hence, we propose the synthesis of dianthra[2,3-b:2,3-b]thiophene (DAT) for applications in organic electronics. Preliminary theoretical calculations on DAT suggest that such a material will have hole mobilities as high as ~ 3 cm2V-1S-1. DAT, therefore, will be promising for applications in organic electronics, namely OFETs, OLEDs, etc. We have synthesized this material, developed collaboration with a research group at Stanford to make devices with it, and detailed studies on its device performances are underway. References: 1. Sheats, J. R. J. Mater. Res.2004, 19, 1974. 2. Butko, V. Y.; Chi, X.; Lang, D. V.; Ramirez. A. P.; Appl. Phys. Lett.2003, 83, 4773. 3. Zhang, Y.; Petta, J. R.; Ambily, S.; Shen, Y.; Ralph, D. C.; Malliaras, G. C. Adv. Mater.2003, 15, 1632. 4. Dimitrakopoulos, C. D.; Kymissis, I.; Purushothaman, S.; Neumayer, D. A.; Duncombe, P. R.; Laibowitz, R. B.; Adv. Mater.1999, 11, 1372. 5. Odom, S. A.; Parkin, S. R.; Anthony, J. E. Org. Lett.2003, 5, 4245. 6. Sundar, V. C.; Zaumseil, J.; Podzorov, V.; Menard, E.; Willett, R. L.; Someya, T.; Gershenson, M. E.; Rodgers, J. A. Science2004, 303, 1644. 7. Reese, C.; Chung, W. J.; Ling, M. M.; Roberts, M.; Bao, Z. N. Appl. Phys. Lett.2006, 89, 202108. 8. Lee, S.; Koo, B.; Shin, J.; Lee, E.; Park, H.; Kim, H. Appl. Phys. Lett.2006, 88, 162109. 9. Yamamoto, T.; Takimiya, K. J. Am. Chem. Soc.2007, 129, 2224. 10. Yamamoto, T.; Takimiya, K. J. Photopolym. Sci. Technol.2007, 20, 57. 11. Sanchez-carrera, R. S.; Atahan, S.; Schrier, J.; Aspuru-Guzik, A. J. Phys. Chem. C 2010, 114, 2334. Part II: The Photo-induced Formation of Quantum Dot – Conductive Polymers (QD:CP) for Application in Photovoltaics. The worlds increasing population and energy consumption has led to a serious issue in dealing with energy supply1,2. A recent study3 suggests that, with current world-wide socio-economic growth, the global energy demand increases at a rate of 2% a year, and an additional 10 terawatts (TW) of energy is needed to sustain the worlds population by 2050. While the present supply of energy is not going to be exhausted in the near future, a shortfall in the supply of energy is impending considering the rapid growth in demand4. Solar energy stands out as the most viable alternative energy resource available because the amount of sunlight that reaches the surface of the Earth each hour is approximately as much as to...

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