Novel porphyrin polymers: synthesis and photoelectric property

Abstract

A series of novel porphyrin monomers with different tail lengths were synthesized through the Alder–Longo method, and the corresponding polymers were successfully synthesized via radical polymerization. The structures of the porphyrin monomers and polymers were all depicted through proton nuclear magnetic resonance (1H-NMR) and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, and the photophysical and electrochemical properties were confirmed through UV–Vis spectroscopy, photoluminescence spectroscopy, and cyclic voltammetry. The results showed that the polymers exhibited a deep highest occupied molecular orbital (HOMO) energy level and a large optical band gap, demonstrating their usefulness in photovoltaic devices. All of the porphyrin monomers formed a typical columnar phase, and the cleaning point of these porphyrin monomers reduced with the increasing length of the alkoxy tail chain. Thermogravimetric analysis demonstrated that the polymers had excellent thermal stability; the decomposition temperature was higher than 400 °C. The UV absorption spectrum of the polymers was between 400 and 670 nm. Compared with the absorption peak of the solution, the absorption peak after film formation presented a certain redshift. The HOMO level was lower than the stable critical level of the conjugated polymer in air (− 5.2 eV), indicating that the polymer is stable in air. In addition, the lowest unoccupied molecular orbital energy level was 0.49–0.64 eV, which was higher than that of the recipient PCBM, indicating that the polymers can be used as a donor material for solar cells.