Conjugated Polymers and DNA for Photovoltaic and Photonic Applications

Date of Completion

January 2011


Chemistry, Polymer




One of the most promising avenues towards improving the efficiency of organic bulk heterojunction (BHJ) solar cells is the design and synthesis of novel donor materials. A series of synthesized alternating copolymers are described, containing 2-decylseleno(3,2-c)thiophene as the donor and fluorene, benzene or benzothiadiazole as the acceptor. The benzothiadiazole-containing copolymer shows the best spectral overlap with the solar spectrum among the three synthesized. Furthermore, the copolymers show deeper HOMO values compared to the homopolymer poly[2-decylseleno(3,2-c)thiophene]. The power conversion efficiency predictions made using Schaber's model reveals that these copolymers are good donor materials for fullerene-based BHJ solar cells. ^ An organic-processable copper phthalocyanine-surfactant complex was prepared as a donor material for BHJ solar cells. The fullerene-based solar cells made using this complex as the donor were compared to those made with poly(3-hexylthiophene) a.k.a P3HT as the donor. Even though the efficiencies of the copper phthalocyanine solar cells were low compared to the P3HT solar cells, this approach provides a facile way to make small molecular solar cells. ^ On a different note, DNA's complex with the cationic surfactant cetyltrimethylammonium (CTMA) bromide was utilized for photonic and environmental applications. The studies on hemicyanine dye (Hemi-22) loaded thin films of DNA-CTMA and polymethylmethacrylate (PMMA) showed that Hemi22 demonstrates high photostability and reduced aggregate formation in DNA-CTMA compared to PMMA. An efficient cascade Förster resonance energy transfer was also realized in a solid-state matrix of DNA-CTMA using a three-dye system, without any necessity for covalent attachments. The improved energy transfer efficiency can be attributed to the ability of DNA to interact with the encapsulated dyes, and to provide the required proximity and orientation. ^ In addition to photonic applications of DNA-CTMA, its environmental applications were explored by preparing a DNA-magnetite hybrid with DNA-CTMA and oleic acid coated magnetite nanoparticles. This hybrid was fabricated into uniform and high surface area nanofibers, which were used to remove organic and inorganic toxicants from aqueous media. The superparamagnetic behavior of the hybrid nanofibers enabled fast and easy separation under an external magnetic field. ^