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ANTS Seminar: Tuesday, January 31, 2006
Switching the ‘Color’ in Variable Gap
Conjugated Polymers
Prof. John Reynolds
Department of Chemistry
University of Florida, Gainesville
By controlling the energy levels of the HOMO and LUMO states
in conjugated polymers, along with the magnitude of the electronic
band gap, optoelectronic properties can be optimized for
specific applications. To this end, we have developed a family
of soluble conjugated polymers with band gaps ranging from
3.2 eV – 1.5 eV and evaluated the utility of these
polymers for device applications. Our use of 3,4-alkylenedioxythiophene
(XDOT) donors, along with cyanovinylene and pyridopyrazine
acceptors has led to the development of a representative
class of soluble narrow gap polymers. Variable gap electrochromic
polymers, where the HOMO and LUMO levels are set for facile
redox chemistry yield multi-color EC materials that can be
processed from aqueous and organic solutions. Novel EC devices
will be demonstrated that efficiently modulate reflectivity
of metal surfaces over broad spectral ranges, while all-polymer
EC devices are flexible and exhibit multi-color states. PCBM-based
solar cells where the HOMO is set for air stability, the
LUMO for excited state donation to the PCBM acceptor, and
the band gap for broad absorption of the solar spectrum will
be discussed. Of special interest are the narrow gap conjugated
polymers that can absorb solar energy most strongly at the
peak of solar photon flux near 1.8 eV. We will discuss fundamental
optical and electrochemical data in order to establish the
band structure of the newly synthesized polymers, along with
presenting results from photovoltaic (PV) as platforms for
materials property optimization. Conjugated polymer blends
using polymers of varied band gap have been used in PV devices
in order to obtain spectral broadening of the absorption
characteristics.
All seminars take place at 500 Technology Square (MIT
Building NE47), First Floor Seminar Room. Any member of
the MIT or Army communities is welcome to attend. For more
information, write to isn@mit.edu.
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