Effect of long alkyl chains of aniline donor on the photovoltaic performance of D-π-A zinc porphyrin for dye-sensitized solar cells

Three novel dyes of JJ1, JJ2, and JJ6 featured zinc porphyrin as a basic core structure; N, N-alkyl-4-(prop-1-yn-1-yl)aniline as an electron donor linked to meso-10-position; 4-(prop-1-yn-1-yl)benzoic acid as an electron acceptor linked to meso-20-position; and 2,6-bis(dodecyloxy)phenyl or 2,6-bis(octyloxy)phenyl respectively linked to meso-5 and meso-15-positions of zinc porphyrin have been synthesized and used for dye-sensitized solar cells. Porphyrin JJ6 featured the shortest alkyl group (C4H9) on the donor, whereas JJ2 contained the longest alkyl groups (C12H25), and JJ1 has a medium length of octyl groups. With these new porphyrin sensitizers, we observed that JJ6 has 7.55% power conversion efficiency under simulated one-sun illumination (AM 1.5 G, 100 mW/cm(2)) with J(SC) = 18.64 mA/cm(2), V-OC = 0.66 V, and fill factor (FF) = 0.61, which was higher than the other two; JJ1 (7.35%) with J(SC) = 18.83 mA/cm(2), V-OC = 0.68 V, and FF = 0.60; and JJ2 (6.33%) with J(SC) = 15.69 mA/cm(2), V-OC = 0.62 V, and FF = 0.65. The power conversion efficiency of JJ6 and JJ1 were higher than JJ2, demonstrating that the lengthy alkyl groups on the aniline cause a decrease in efficiency of the devices.