E. Muller, A. Bhuwalka and M. Jeffries-EL
Department of Chemistry, Iowa State University, 50011, Ames, IA USA Presenting author: ewmuller@iastate.edu
The continued development of conjugated polymers has led to breakthroughs in the design and application of organic semiconductor materials in devices ranging from light emitting diodes to photovoltaic cells. In order to develop new materials that are viable for commercial applications, a number of new structures have been developed in an attempt to improve upon the conjugated materials that are currently in use. The electron-donating benzo[1,2-b:4,5-b′]dithiophene (BDT) system has attracted interest due to its highly planar structure, facilitating improved 𝝅-𝝅 stacking between polymer chains which in turn leads to enhanced charge carrier mobility values.[1-3] Devices with PCE values approaching 8% have been obtained using BDT monomers as donating units in donor-acceptor copolymers, and BDT has seen widespread adoption as a benchmark donor unit in the development of new high-performing conjugated polymers.[2, 3] Recently our group explored the use of benzo[1,2-b:4,5-b’]difuran (BDF) as a replacement for BDT in conjugated polymers. The positive attributes of BDT largely carry over into BDF systems, while the smaller atomic radius of oxygen compared to sulfur is predicted to reduce steric strain in the system and thus increase the planarity as well as the extent of conjugation within the system. Calculations have predicted BDF systems to contain narrower band-gaps than their BDT analogues, and until recently the limitations of BDF were largely synthetic in nature. We have developed synthetic routes to BDF systems which entail few steps, give high yields, and enable reasonable substrate scope at different positions of the BDF monomer. In addition to BDF based materials, we have developed a high yielding synthetic approach to naphtho[1,2-b:6,7-b’]difuran (NDF) based materials which have not been widely explored as donor units in conjugated materials. The NDF monomer is predicted to be highly planar with a longer conjugation length than BDF analogues, and the incorporation of both NDF and BDF into copolymer systems has been explored within our group. Further exploration of new donor-acceptor conjugated polymers using BDF and NDF monomers along with various electron-deficient comonomers is underway within our group for use in photovoltaic devices.
References
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