Synthesis of Porphyrin-Appended Poly(fluorene-alt-triphenylamine)s: Effect of Appending Groups on Optical and Electrochemical Properties

Series of poly(fluorene-alt-triphenylamine)s having 5 and 10% equivalent of porphyrin appended through oxyethylene spacer in carbazole and aldehyde as side chain in triphenylamine unit (P2-P5 CHO) were synthesized using Suzuki polycondensation. The synthesized polymers were compared with their parent polymer (P1 CHO). The effect of side chains in polymer backbone was studied by using aldehyde and dicyanomethane as side chain in triphenylamine moiety of polymer. Further, the role of spatial arrangement of appended porphyrin group on the polymer's optical and electrochemical properties was also studied. Thermal studies of the polymers showed that, these polymers were thermally stable up to 200 degrees C. Optical absorption studies of the porphyrin appended polymers showed absorption maxima at around 301 nm, 375 nm, and 421 nm with Q bands of porphyrin. As thin film, photoluminescence emission studies of the polymers showed emission maxima at around 650 and 719nm. Electrochemical study reveals that m-phenyloxy trisphenylporphyrin appended polymers showed HOMO energy level at around -5.45eV and LUMO energy level at around -3.45eV. While, p-phenyloxy trisphenylporphyrin appended polymers showed a marginal shift in HOMO and LUMO energy levels. Photovoltaic studies of the porphyrin appended polymer showed up to 0.1% power conversion efficiency with an open circuit voltage of 0.76V and the details are reported.