Linear and star branched perylene-containing polyimides: Synthesis, characterization, and photovoltaic properties of novel donor-acceptor dyes used in solar cell

A series of novel linear and star branched triphenylamine-containing aromatic polyimides (AI, AII, AIII) were designed and synthesized by the condensation of 4-aminotriphenylamine(I), 4,4′-diamino triphenylamine(II), 4,4′,4″-triamino triphenyl-amine(III) with perylene-3,4,9,10-tetra- carboxylic dianhydride to investigate the influence of topological structure on the energy levels and photophysical performance. The polyimides were characterized by elemental analysis, FTIR, and ¹H-NMR. The onset temperatures for 5% weight loss determined by thermoanalysis were between 415 and 428°C. The results of UV-vis spectra, quantum chemical calculation, and cyclic voltammetry revealed that introduction of triphenylamine group changed the energy levels of entire dye system. The aggregation way of polymers was also studied by the methods of UV-vis spectra, X-ray diffraction (XRD), atom force microscopy, and the molecular simulation. The dye-sensitized solar cells prepared by using the series of dyes showed big photoelectric response.