Synthesis, Characterization, Electrochemical and Optoelectronic Properties and LED Device Fabrication of Low Band-Gap Donor-Acceptor Organic Semiconducting Small Molecules

Abstract

Organic fluorophores that exhibit efficient emission in the NIR region, especially in the solid state, are scarce. The design of organic materials towards efficient solid state emission has gained immense importance [1] due to their applications in various fields, such as organic light emitting devices (OLEDs), flat panel displays, organic solid-state lasers and fluorescent sensors [2]. Among the various fluorophores, red emitters have acquired a great deal of importance since red is one of the three primary colors used for white light emission [3]. The development of p-conjugated systems emitting in the NIR region is of great importance as they are often used in bio-imaging, laser printers, optical disks, plasma panel displays and heat absorbers [4]. For low energy emission such as red and NIR, planar molecular architecture with extended conjugation is inevitable for lowering the band-gap. But this extended planar architecture often leads to a strong intermolecular p-p interaction, a detrimental phenomenon by which the molecule loses its excitation energy through a non-radiative emission, resulting in weak emission. In the light of these facts it is a challenging task to design molecules that would exhibit efficient emission in the solid state, especially in the red to NIR region. This presentation will discourse upon the synthesis, characterization, electrochemical, optoelectronic properties and LED device fabrication of low band-gap donor-acceptor organic semiconducting small molecules that exhibit solid state emission in the yellow to NIR region. References a) Shimizu, M.; Hiyama, T. Chem. Asian. J. 2010, 5, 1516; b) Sreejith, S.; Divya, K. P.; Ajayghosh, A. Chem. Commun. 2008, 2903; c) Zhang, Z.; Xu, B.; Su, J.; Shen, L.; Xie, Y.; Tian, H. Angew. Chem. 2011, 123, 11858; d) Zhou, Y.; Kim, J. W.; Kim, M. J.; Son, W. J.; Han, S. J.; Kim, H. N.; Han, S.; Kim, Y.; Lee, C.; Kim, S. J.; Kim, D. H.; Kim, J. J.; Yoon, J. Org. Lett. 2010, 12,1272.a) Kulkarni, A. P.; Tonzola, C. J.; Babel, A.; Jenekhe, S. A. Chem. Mater. 2004, 16, 4556; b) Justel, T.; Nikol, H.; Ronda, C. Angew. Chem. 1998, 110, 3250; c) Samuel, I. D. W.; Turnbull, G. A. Chem. Rev. 2007, 107, 1272; d) Zhang, S. W.; Swager, T. M. J. Am. Chem. Soc. 2003, 125, 3420.a) Adhikari, R. M.; Duan, I.; Hou, L.; Qiu, Y.; Neckers, D. C.; Sha, B. K. Chem. Mater. 2009, 21, 4638; b) Park, M. J.; Lee, J.; Park, J. H.; Lee, S. K.; Lee, J. I.; Chu, H. Y.; Hwang, D. H.; Shim, H. K. Macromolecules. 2008, 41, 3063.Qian, G.; Wang, Z. U. Chem. Asian J. 2010, 5, 1006. Figure 1