Conjugated polymers provide a unique encompassing set of structurally tunable optical, electronic transport, and redox properties that allows their present and potential use in a host of applications which span, field effect transistors, light emitting diodes, electrochromism, solar cells, and photodetectors, along with batteries and supercapacitors. In this lecture, we will address the synthesis and optimization of the morphology of solution processed ?-conjugated oligomers and polymers, as they are applied in organic electronic devices. We seek to address the processing gap that is holding back developments in solid-state organic photovoltaics, along with redox active electrochromism and charge storage. Processing of these materials is carried out using a variety of solution methods including spin-coating, spray-coating, blade-coating, slot die coating and ink jet printing. Using thiophene-based donors and linkers, we use a Donor-Acceptor (D-A) arrangement with isoindigo, thienoisoindigo, and diketopyrrolopyrrole (DPP) acceptors to prepare photoactive materials with AM 1.5 power conversion efficiencies ranging from 5 to 8.5%.1 Film solidification rates are found to be rapid after initial formation of a super-saturated solution. We will use the reversible redox switching of electron-rich polymers to demonstrate electrical charge storage, potentially useful in supercapacitor applications.2,3 The optical absorbance spectra of electron-rich pi-conjugated oligomers and polymers can be tuned to yield electrochromic materials of all colors that can be switched to highly transmissive forms as desired for absorptive/reflective (display type) and absorptive/transmissive (window type) devices. We will demonstrate how structural design and synthesis of fully conjugated polymers, along with mixing in polymer blends, has been used to complete the color palette of electrochromic polymers (ECPs) needed for subtractive color mixing.4 Colorimetric tuning (using the L*a*b* color space) using a combination of electron rich and poor units, in conjunction with employing subtle changes in steric strain or relaxation, allows for the enhancement of the neutral form color vibrancy, and the transmissivity of the oxidized forms. We have developed a set of fast switching, high contrast black and brown ECP blends. We use these brown blends to demonstrate the attractiveness of ECPs in window-type electrochromic devices (ECDs) as active materials in color changing eyewear.5 Finally, we combine our ECP and OPV technologies into possibilities for solar powered electrochromic windows.
Dr. John R. Reynolds is a Professor of Chemistry and Biochemistry, and Materials Science and Engineering at the Georgia Institute of Technology with expertise in polymer chemistry. He serves as a member of the Center for Organic Photonics and Electronics (COPE) and Director of the Georgia Tech Polymer Network (GTPN). His research interests have involved electrically conducting and electroactive conjugated polymers for over 35 years with work focused to the development of new polymers by manipulating their fundamental organic structure in order to control their optoelectronic and redox properties. His group has been heavily involved in developing new polyheterocycles for visible and infrared light electrochromism, along with light emission from polymer and composite LEDs (both visible and near-infrared) and light emitting electrochemical cells (LECs). Further work is directed to using organic polymers and oligomers in charge storing supercapacitors and photovoltaic cells. Reynolds obtained his M.S. (1982) and Ph.D. (1984) degrees from the University of Massachusetts in Polymer Science and Engineering, he has published over 350 peer-reviewed scientific papers, has 35 patents issued and ~10 patents pending, and served as co-editor of the “Handbook of Conducting Polymers” which was published in 2007. He serves on the editorial board for the journals ACS Applied Materials and Interfaces, ACS Central Science, Macromolecular Rapid Communications, Polymers for Advanced Technologies, and the Journal of Macromolecular Science, Chemistry. John has been married since October of 1986, has three children, and he and his wife make their home in Dunwoody GA. He can be reached by e-mail at reynolds at chemistry.gatech.edu or see http://ww2.chemistry.gatech.edu/reynolds/