Synthesis of bipyridyl-porphyrins as dye-photosensitizers for solar cells

Abstract

Bipyridylporphyrin derivatives were designed and synthesized for use as dye-sensitizer in dye-sensitized solar cells (DSSCs). Bipyridylporphyrin derivatives composed of Donor-Acceptor system (D-A) based on porphyrin moiety as the electron donor (D) and bipyridyl moiety as the electron-acceptor (A). All compounds were characterized and confirmed structures by NMR, IR, Mass spectroscopy and Elemental Analysis. From the experimental and the theoretical calculation, the HOMO and LUMO energy levels of all compounds are in range, which match well with the CB band of TiO₂ favoring electron injection from the exited dyes (s*) to TiO₂ and the redox potential of the I⁻/I₃⁻ electrolyte favoring electron injection from the electrolyte to the cationic dyes (S³). Upon the studies of the photovoltaic performance measurements, a overall solar-to-electric conversion efficiency under AM 1.5 irradiation and use 0.10 M LiI, 0.05 M I₂, 0.40 M pyridine and 0.60 M TPAI as electrolytic system of 0.05, 0.28, 0.38 and 0.05 % was achieved based on the bipyridylporphyrin dyes A5, A6, A7 and A8, respectively, which were lower than the efficiency (5.97%) obtained from the standard dye N719. From the short circuit photocurrent density of the bipyridylporphyrin dyes A5, A6, A7 and A8, showed lower than the standard dye N719, possibly due to poorer electron injection from bipyridylporphyrin dyes onto the TiO₂ surface. In addition, the efficiency of the dye was improved by adding chenodeoxycholic acid (CDCA) as the coadsorbant.